v45-0005-Row-pattern-recognition-patch-executor-and-comma.patch
application/octet-stream
Filename: v45-0005-Row-pattern-recognition-patch-executor-and-comma.patch
Type: application/octet-stream
Part: 4
Message:
Re: Row pattern recognition
Patch
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GET /api/v1/attachments/:id/patch
the parsed metadata as JSON — format, series position, per-file stats; never the diff bytes.
API reference →
Format: format-patch
Series: patch v45-0005
Subject: Row pattern recognition patch (executor and commands).
| File | + | − |
|---|---|---|
| src/backend/commands/explain.c | 461 | 0 |
| src/backend/executor/execRPR.c | 3037 | 0 |
| src/backend/executor/Makefile | 1 | 0 |
| src/backend/executor/meson.build | 1 | 0 |
| src/backend/executor/nodeWindowAgg.c | 841 | 9 |
| src/backend/utils/adt/windowfuncs.c | 23 | 2 |
| src/include/catalog/pg_proc.dat | 6 | 0 |
| src/include/executor/execRPR.h | 40 | 0 |
| src/include/nodes/execnodes.h | 118 | 0 |
From d09207b33f2f16ef9cadc015cc44c579635857ce Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Wed, 18 Mar 2026 20:16:17 +0900
Subject: [PATCH v45 5/8] Row pattern recognition patch (executor and
commands).
---
src/backend/commands/explain.c | 461 ++++
src/backend/executor/Makefile | 1 +
src/backend/executor/execRPR.c | 3037 ++++++++++++++++++++++++++
src/backend/executor/meson.build | 1 +
src/backend/executor/nodeWindowAgg.c | 850 ++++++-
src/backend/utils/adt/windowfuncs.c | 25 +-
src/include/catalog/pg_proc.dat | 6 +
src/include/executor/execRPR.h | 40 +
src/include/nodes/execnodes.h | 118 +
9 files changed, 4528 insertions(+), 11 deletions(-)
create mode 100644 src/backend/executor/execRPR.c
create mode 100644 src/include/executor/execRPR.h
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 296ea8a1ed2..36d2648ccac 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -29,6 +29,7 @@
#include "nodes/extensible.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
+#include "optimizer/rpr.h"
#include "parser/analyze.h"
#include "parser/parsetree.h"
#include "rewrite/rewriteHandler.h"
@@ -118,6 +119,20 @@ static void show_window_def(WindowAggState *planstate,
static void show_window_keys(StringInfo buf, PlanState *planstate,
int nkeys, AttrNumber *keycols,
List *ancestors, ExplainState *es);
+static void append_rpr_quantifier(StringInfo buf, RPRPatternElement *elem);
+static char *deparse_rpr_pattern(RPRPattern *pattern);
+static void deparse_rpr_elements(RPRPattern *pattern, int *idx,
+ StringInfoData *buf, RPRDepth groupDepth,
+ RPRDepth *prevDepth, bool *needSpace);
+static void deparse_rpr_group(RPRPattern *pattern, int *idx,
+ StringInfoData *buf, RPRDepth *prevDepth,
+ bool *needSpace);
+static void deparse_rpr_alt(RPRPattern *pattern, int *idx,
+ StringInfoData *buf, RPRDepth *prevDepth,
+ bool *needSpace, List **altSeps);
+static void deparse_rpr_var(RPRPattern *pattern, int *idx,
+ StringInfoData *buf, RPRDepth *prevDepth,
+ bool *needSpace, List **altSeps);
static void show_storage_info(char *maxStorageType, int64 maxSpaceUsed,
ExplainState *es);
static void show_tablesample(TableSampleClause *tsc, PlanState *planstate,
@@ -128,6 +143,7 @@ static void show_incremental_sort_info(IncrementalSortState *incrsortstate,
static void show_hash_info(HashState *hashstate, ExplainState *es);
static void show_material_info(MaterialState *mstate, ExplainState *es);
static void show_windowagg_info(WindowAggState *winstate, ExplainState *es);
+static void show_rpr_nfa_stats(WindowAggState *winstate, ExplainState *es);
static void show_ctescan_info(CteScanState *ctescanstate, ExplainState *es);
static void show_table_func_scan_info(TableFuncScanState *tscanstate,
ExplainState *es);
@@ -2891,6 +2907,284 @@ show_sortorder_options(StringInfo buf, Node *sortexpr,
}
}
+/*
+ * Append quantifier suffix for a pattern element.
+ */
+static void
+append_rpr_quantifier(StringInfo buf, RPRPatternElement *elem)
+{
+ /* Append quantifier if not {1,1} */
+ if (elem->min == 0 && elem->max == RPR_QUANTITY_INF)
+ appendStringInfoChar(buf, '*');
+ else if (elem->min == 1 && elem->max == RPR_QUANTITY_INF)
+ appendStringInfoChar(buf, '+');
+ else if (elem->min == 0 && elem->max == 1)
+ appendStringInfoChar(buf, '?');
+ else if (elem->max == RPR_QUANTITY_INF)
+ appendStringInfo(buf, "{%d,}", elem->min);
+ else if (elem->min == elem->max && elem->min != 1)
+ appendStringInfo(buf, "{%d}", elem->min);
+ else if (elem->min != 1 || elem->max != 1)
+ appendStringInfo(buf, "{%d,%d}", elem->min, elem->max);
+
+ if (RPRElemIsReluctant(elem))
+ {
+ if (elem->min == 1 && elem->max == 1)
+ appendStringInfo(buf, "{1}"); /* make reluctant ? unambiguous */
+ appendStringInfoChar(buf, '?');
+ }
+
+ /* Append absorption markers: " for judgment point, ' for branch only */
+ if (RPRElemIsAbsorbable(elem))
+ {
+ Assert(elem->max == RPR_QUANTITY_INF);
+ appendStringInfoChar(buf, '"');
+ }
+ else if (RPRElemIsAbsorbableBranch(elem))
+ appendStringInfoChar(buf, '\'');
+}
+
+/*
+ * Deparse a compiled RPRPattern (bytecode) back to pattern string.
+ *
+ * Walks the flat bytecode array using mutual recursion: deparse_rpr_elements
+ * processes sequential elements, and deparse_rpr_group handles BEGIN...END
+ * groups by recursing back into deparse_rpr_elements for the group content.
+ */
+static char *
+deparse_rpr_pattern(RPRPattern *pattern)
+{
+ StringInfoData buf;
+ int idx = 0;
+ RPRDepth prevDepth = 0;
+ bool needSpace = false;
+
+ Assert(pattern != NULL && pattern->numElements >= 2);
+
+ initStringInfo(&buf);
+
+ deparse_rpr_elements(pattern, &idx, &buf, RPR_DEPTH_NONE,
+ &prevDepth, &needSpace);
+
+ /* Close remaining open parens */
+ while (prevDepth > 0)
+ {
+ appendStringInfoChar(&buf, ')');
+ prevDepth--;
+ }
+
+ return buf.data;
+}
+
+/*
+ * Process pattern elements sequentially until FIN or END at groupDepth.
+ *
+ * When groupDepth >= 0, stops at the matching END element (leaving idx
+ * pointing to it) so the caller (deparse_rpr_group) can consume it.
+ * When groupDepth < 0, processes until FIN (top-level call).
+ */
+static void
+deparse_rpr_elements(RPRPattern *pattern, int *idx, StringInfoData *buf,
+ RPRDepth groupDepth, RPRDepth *prevDepth,
+ bool *needSpace)
+{
+ List *altSeps = NIL; /* pending alternation separator indices */
+
+ while (*idx < pattern->numElements)
+ {
+ RPRPatternElement *elem = &pattern->elements[*idx];
+
+ if (RPRElemIsFin(elem))
+ break;
+
+ /* Stop at END matching our group depth; caller handles it */
+ if (RPRElemIsEnd(elem) && elem->depth == groupDepth)
+ break;
+
+ /* Alternation separator */
+ if (list_member_int(altSeps, *idx))
+ {
+ /* Close parens to match separator depth first */
+ while (*prevDepth > elem->depth)
+ {
+ appendStringInfoChar(buf, ')');
+ (*prevDepth)--;
+ }
+ appendStringInfoString(buf, " | ");
+ *needSpace = false;
+ altSeps = list_delete_int(altSeps, *idx);
+ }
+
+ /* Dispatch to element-type handlers */
+ if (RPRElemIsAlt(elem))
+ deparse_rpr_alt(pattern, idx, buf, prevDepth,
+ needSpace, &altSeps);
+ else if (RPRElemIsBegin(elem))
+ deparse_rpr_group(pattern, idx, buf, prevDepth,
+ needSpace);
+ else if (RPRElemIsVar(elem))
+ deparse_rpr_var(pattern, idx, buf, prevDepth,
+ needSpace, &altSeps);
+ }
+ list_free(altSeps);
+}
+
+/*
+ * Process a BEGIN...END group.
+ *
+ * Consumes BEGIN, recurses into deparse_rpr_elements for group content,
+ * then consumes END and outputs the group quantifier.
+ *
+ * When the group wraps a single ALT with no siblings, the group-level
+ * parenthesis is suppressed since the ALT-to-children depth transition
+ * already provides it (avoids double parens like "((a | b))+").
+ */
+static void
+deparse_rpr_group(RPRPattern *pattern, int *idx, StringInfoData *buf,
+ RPRDepth *prevDepth, bool *needSpace)
+{
+ RPRPatternElement *begin = &pattern->elements[*idx];
+ RPRDepth childDepth = begin->depth + 1;
+ bool singleAlt = false;
+ RPRPatternElement *end;
+
+ /*
+ * Check if this group wraps a single ALT with no siblings. Scan from
+ * after ALT to END: if no element at childDepth exists, the ALT is the
+ * sole child.
+ */
+ if (*idx + 1 < pattern->numElements &&
+ RPRElemIsAlt(&pattern->elements[*idx + 1]))
+ {
+ int j;
+
+ singleAlt = true;
+ for (j = *idx + 2; j < pattern->numElements; j++)
+ {
+ RPRPatternElement *e = &pattern->elements[j];
+
+ if (RPRElemIsEnd(e) && e->depth == begin->depth)
+ break;
+ if (e->depth <= childDepth)
+ {
+ singleAlt = false;
+ break;
+ }
+ }
+ }
+
+ /* Open group paren (unless single ALT provides it) */
+ if (!singleAlt)
+ {
+ if (*needSpace)
+ appendStringInfoChar(buf, ' ');
+ appendStringInfoChar(buf, '(');
+ *needSpace = false;
+ }
+ *prevDepth = childDepth;
+ (*idx)++; /* consume BEGIN */
+
+ /* Process group children; stops at matching END */
+ deparse_rpr_elements(pattern, idx, buf, begin->depth,
+ prevDepth, needSpace);
+
+ /* Consume END and output quantifier */
+ Assert(*idx < pattern->numElements);
+ end = &pattern->elements[*idx];
+ Assert(RPRElemIsEnd(end) && end->depth == begin->depth);
+
+ while (*prevDepth > end->depth + 1)
+ {
+ appendStringInfoChar(buf, ')');
+ (*prevDepth)--;
+ }
+ if (!singleAlt)
+ appendStringInfoChar(buf, ')');
+ append_rpr_quantifier(buf, end);
+ *prevDepth = end->depth;
+ *needSpace = true;
+ (*idx)++; /* consume END */
+}
+
+/*
+ * Process an ALT element: adjust depth parens and register separator positions.
+ */
+static void
+deparse_rpr_alt(RPRPattern *pattern, int *idx, StringInfoData *buf,
+ RPRDepth *prevDepth, bool *needSpace, List **altSeps)
+{
+ RPRPatternElement *elem = &pattern->elements[*idx];
+
+ /* Close parens for depth decrease */
+ while (*prevDepth > elem->depth)
+ {
+ appendStringInfoChar(buf, ')');
+ (*prevDepth)--;
+ *needSpace = true;
+ }
+
+ /* Open parens up to ALT's depth */
+ while (*prevDepth < elem->depth)
+ {
+ if (*needSpace)
+ appendStringInfoChar(buf, ' ');
+ appendStringInfoChar(buf, '(');
+ (*prevDepth)++;
+ *needSpace = false;
+ }
+
+ /* Register next alternation separator position */
+ if (elem->next != RPR_ELEMIDX_INVALID)
+ {
+ RPRPatternElement *firstElem = &pattern->elements[elem->next];
+
+ if (firstElem->jump != RPR_ELEMIDX_INVALID)
+ *altSeps = lappend_int(*altSeps, firstElem->jump);
+ }
+ if (elem->jump != RPR_ELEMIDX_INVALID)
+ *altSeps = lappend_int(*altSeps, elem->jump);
+ (*idx)++;
+}
+
+/*
+ * Process a VAR element: adjust depth parens and output variable name.
+ */
+static void
+deparse_rpr_var(RPRPattern *pattern, int *idx, StringInfoData *buf,
+ RPRDepth *prevDepth, bool *needSpace, List **altSeps)
+{
+ RPRPatternElement *elem = &pattern->elements[*idx];
+
+ /* Open parens for depth increase */
+ while (*prevDepth < elem->depth)
+ {
+ if (*needSpace)
+ appendStringInfoChar(buf, ' ');
+ appendStringInfoChar(buf, '(');
+ (*prevDepth)++;
+ *needSpace = false;
+ }
+
+ /* Close parens for depth decrease */
+ while (*prevDepth > elem->depth)
+ {
+ appendStringInfoChar(buf, ')');
+ (*prevDepth)--;
+ }
+
+ if (*needSpace)
+ appendStringInfoChar(buf, ' ');
+
+ Assert(elem->varId < pattern->numVars);
+ appendStringInfoString(buf, pattern->varNames[elem->varId]);
+ append_rpr_quantifier(buf, elem);
+ *needSpace = true;
+
+ if (elem->jump != RPR_ELEMIDX_INVALID)
+ *altSeps = lappend_int(*altSeps, elem->jump);
+ (*idx)++;
+}
+
/*
* Show the window definition for a WindowAgg node.
*/
@@ -2949,6 +3243,18 @@ show_window_def(WindowAggState *planstate, List *ancestors, ExplainState *es)
appendStringInfoChar(&wbuf, ')');
ExplainPropertyText("Window", wbuf.data, es);
pfree(wbuf.data);
+
+ /* Show Row Pattern Recognition pattern if present */
+ if (wagg->rpPattern != NULL)
+ {
+ char *patternStr = deparse_rpr_pattern(wagg->rpPattern);
+
+ if (patternStr != NULL)
+ {
+ ExplainPropertyText("Pattern", patternStr, es);
+ pfree(patternStr);
+ }
+ }
}
/*
@@ -3501,6 +3807,7 @@ show_windowagg_info(WindowAggState *winstate, ExplainState *es)
{
char *maxStorageType;
int64 maxSpaceUsed;
+ WindowAgg *wagg = (WindowAgg *) winstate->ss.ps.plan;
Tuplestorestate *tupstore = winstate->buffer;
@@ -3513,6 +3820,160 @@ show_windowagg_info(WindowAggState *winstate, ExplainState *es)
tuplestore_get_stats(tupstore, &maxStorageType, &maxSpaceUsed);
show_storage_info(maxStorageType, maxSpaceUsed, es);
+
+ /* Show NFA statistics for Row Pattern Recognition */
+ if (wagg->rpPattern != NULL)
+ show_rpr_nfa_stats(winstate, es);
+}
+
+/*
+ * Show NFA statistics for Row Pattern Recognition on WindowAgg node.
+ */
+static void
+show_rpr_nfa_stats(WindowAggState *winstate, ExplainState *es)
+{
+ if (es->format != EXPLAIN_FORMAT_TEXT)
+ {
+ /* State and context counters */
+ ExplainPropertyInteger("NFA States Peak", NULL, winstate->nfaStatesMax, es);
+ ExplainPropertyInteger("NFA States Total", NULL, winstate->nfaStatesTotalCreated, es);
+ ExplainPropertyInteger("NFA States Merged", NULL, winstate->nfaStatesMerged, es);
+ ExplainPropertyInteger("NFA Contexts Peak", NULL, winstate->nfaContextsMax, es);
+ ExplainPropertyInteger("NFA Contexts Total", NULL, winstate->nfaContextsTotalCreated, es);
+ ExplainPropertyInteger("NFA Contexts Absorbed", NULL, winstate->nfaContextsAbsorbed, es);
+ ExplainPropertyInteger("NFA Contexts Skipped", NULL, winstate->nfaContextsSkipped, es);
+ ExplainPropertyInteger("NFA Contexts Pruned", NULL, winstate->nfaContextsPruned, es);
+
+ /* Match/mismatch counts and length statistics */
+ ExplainPropertyInteger("NFA Matched", NULL, winstate->nfaMatchesSucceeded, es);
+ ExplainPropertyInteger("NFA Mismatched", NULL, winstate->nfaMatchesFailed, es);
+ if (winstate->nfaMatchesSucceeded > 0)
+ {
+ ExplainPropertyInteger("NFA Match Length Min", NULL, winstate->nfaMatchLen.min, es);
+ ExplainPropertyInteger("NFA Match Length Max", NULL, winstate->nfaMatchLen.max, es);
+ ExplainPropertyFloat("NFA Match Length Avg", NULL,
+ (double) winstate->nfaMatchLen.total / winstate->nfaMatchesSucceeded, 1,
+ es);
+ }
+ if (winstate->nfaMatchesFailed > 0)
+ {
+ ExplainPropertyInteger("NFA Mismatch Length Min", NULL, winstate->nfaFailLen.min, es);
+ ExplainPropertyInteger("NFA Mismatch Length Max", NULL, winstate->nfaFailLen.max, es);
+ ExplainPropertyFloat("NFA Mismatch Length Avg", NULL,
+ (double) winstate->nfaFailLen.total / winstate->nfaMatchesFailed, 1,
+ es);
+ }
+
+ /* Absorbed/skipped context length statistics */
+ if (winstate->nfaContextsAbsorbed > 0)
+ {
+ ExplainPropertyInteger("NFA Absorbed Length Min", NULL, winstate->nfaAbsorbedLen.min, es);
+ ExplainPropertyInteger("NFA Absorbed Length Max", NULL, winstate->nfaAbsorbedLen.max, es);
+ ExplainPropertyFloat("NFA Absorbed Length Avg", NULL,
+ (double) winstate->nfaAbsorbedLen.total / winstate->nfaContextsAbsorbed, 1,
+ es);
+ }
+ if (winstate->nfaContextsSkipped > 0)
+ {
+ ExplainPropertyInteger("NFA Skipped Length Min", NULL, winstate->nfaSkippedLen.min, es);
+ ExplainPropertyInteger("NFA Skipped Length Max", NULL, winstate->nfaSkippedLen.max, es);
+ ExplainPropertyFloat("NFA Skipped Length Avg", NULL,
+ (double) winstate->nfaSkippedLen.total / winstate->nfaContextsSkipped, 1,
+ es);
+ }
+ }
+ else
+ {
+ /* State and context counters */
+ ExplainIndentText(es);
+ appendStringInfo(es->str,
+ "NFA States: " INT64_FORMAT " peak, " INT64_FORMAT " total, " INT64_FORMAT " merged\n",
+ winstate->nfaStatesMax,
+ winstate->nfaStatesTotalCreated,
+ winstate->nfaStatesMerged);
+ ExplainIndentText(es);
+ appendStringInfo(es->str,
+ "NFA Contexts: " INT64_FORMAT " peak, " INT64_FORMAT " total, " INT64_FORMAT " pruned\n",
+ winstate->nfaContextsMax,
+ winstate->nfaContextsTotalCreated,
+ winstate->nfaContextsPruned);
+
+ /* Match/mismatch counts with length min/max/avg */
+ ExplainIndentText(es);
+ appendStringInfo(es->str, "NFA: ");
+ if (winstate->nfaMatchesSucceeded > 0)
+ {
+ double avgLen = (double) winstate->nfaMatchLen.total / winstate->nfaMatchesSucceeded;
+
+ appendStringInfo(es->str,
+ INT64_FORMAT " matched (len " INT64_FORMAT "/" INT64_FORMAT "/%.1f)",
+ winstate->nfaMatchesSucceeded,
+ winstate->nfaMatchLen.min,
+ winstate->nfaMatchLen.max,
+ avgLen);
+ }
+ else
+ {
+ appendStringInfo(es->str, "0 matched");
+ }
+ if (winstate->nfaMatchesFailed > 0)
+ {
+ double avgFail = (double) winstate->nfaFailLen.total / winstate->nfaMatchesFailed;
+
+ appendStringInfo(es->str,
+ ", " INT64_FORMAT " mismatched (len " INT64_FORMAT "/" INT64_FORMAT "/%.1f)",
+ winstate->nfaMatchesFailed,
+ winstate->nfaFailLen.min,
+ winstate->nfaFailLen.max,
+ avgFail);
+ }
+ else
+ {
+ appendStringInfo(es->str, ", 0 mismatched");
+ }
+ appendStringInfoChar(es->str, '\n');
+
+ /* Absorbed/skipped context length statistics */
+ if (winstate->nfaContextsAbsorbed > 0 || winstate->nfaContextsSkipped > 0)
+ {
+ ExplainIndentText(es);
+ appendStringInfo(es->str, "NFA: ");
+
+ if (winstate->nfaContextsAbsorbed > 0)
+ {
+ double avgAbsorbed = (double) winstate->nfaAbsorbedLen.total / winstate->nfaContextsAbsorbed;
+
+ appendStringInfo(es->str,
+ INT64_FORMAT " absorbed (len " INT64_FORMAT "/" INT64_FORMAT "/%.1f)",
+ winstate->nfaContextsAbsorbed,
+ winstate->nfaAbsorbedLen.min,
+ winstate->nfaAbsorbedLen.max,
+ avgAbsorbed);
+ }
+ else
+ {
+ appendStringInfo(es->str, "0 absorbed");
+ }
+
+ if (winstate->nfaContextsSkipped > 0)
+ {
+ double avgSkipped = (double) winstate->nfaSkippedLen.total / winstate->nfaContextsSkipped;
+
+ appendStringInfo(es->str,
+ ", " INT64_FORMAT " skipped (len " INT64_FORMAT "/" INT64_FORMAT "/%.1f)",
+ winstate->nfaContextsSkipped,
+ winstate->nfaSkippedLen.min,
+ winstate->nfaSkippedLen.max,
+ avgSkipped);
+ }
+ else
+ {
+ appendStringInfo(es->str, ", 0 skipped");
+ }
+
+ appendStringInfoChar(es->str, '\n');
+ }
+ }
}
/*
diff --git a/src/backend/executor/Makefile b/src/backend/executor/Makefile
index 11118d0ce02..eeed9a904e5 100644
--- a/src/backend/executor/Makefile
+++ b/src/backend/executor/Makefile
@@ -26,6 +26,7 @@ OBJS = \
execPartition.o \
execProcnode.o \
execReplication.o \
+ execRPR.o \
execSRF.o \
execScan.o \
execTuples.o \
diff --git a/src/backend/executor/execRPR.c b/src/backend/executor/execRPR.c
new file mode 100644
index 00000000000..0d5ba7516e9
--- /dev/null
+++ b/src/backend/executor/execRPR.c
@@ -0,0 +1,3037 @@
+/*-------------------------------------------------------------------------
+ *
+ * execRPR.c
+ * NFA-based Row Pattern Recognition engine for window functions.
+ *
+ * This file implements the NFA execution engine for the ROWS BETWEEN
+ * PATTERN clause (SQL Standard Feature R020: Row Pattern Recognition in
+ * Window Functions).
+ *
+ * The engine executes the compiled RPRPattern structure directly, avoiding
+ * regex compilation overhead. It is called by nodeWindowAgg.c and exposes
+ * the interface declared in executor/execRPR.h.
+ *
+ *
+ * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ * src/backend/executor/execRPR.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "executor/execRPR.h"
+#include "executor/executor.h"
+#include "optimizer/rpr.h"
+#include "utils/memutils.h"
+
+/*
+ * ============================================================================
+ * PostgreSQL Row Pattern Recognition: Flat-Array Stream NFA Guide
+ * ============================================================================
+ *
+ * Target audience: Developers with a basic understanding of the PostgreSQL
+ * executor and planner architecture
+ *
+ * Scope: The entire process from PATTERN/DEFINE clause parsing to NFA
+ * runtime execution
+ *
+ * Related code:
+ * - src/backend/parser/parse_rpr.c (parser phase)
+ * - src/backend/optimizer/plan/rpr.c (optimizer phase)
+ * - src/backend/executor/nodeWindowAgg.c (executor phase, window agg)
+ * - src/backend/executor/execRPR.c (executor phase, NFA engine)
+ * - src/include/executor/execRPR.h (NFA public API)
+ * - src/include/nodes/plannodes.h (plan node definitions)
+ * - src/include/nodes/execnodes.h (execution state definitions)
+ * - src/include/optimizer/rpr.h (types and constants)
+ *
+ * ============================================================================
+ *
+ * What is a Flat-Array Stream NFA?
+ *
+ * The NFA in this implementation is not a traditional state-transition graph
+ * but a flat array of fixed-size 16-byte elements. At runtime, it processes
+ * the row stream in a forward-only manner, expanding epsilon transitions
+ * eagerly without backtracking.
+ *
+ * - Flat-Array: Pattern compiled into a flat array,
+ * not a graph (Chapter IV)
+ * - Stream: Rows consumed sequentially in one direction,
+ * never revisited (Chapter XII)
+ * - NFA: Nondeterministic execution where multiple states
+ * coexist within a single context (Chapter VI)
+ *
+ * Chapter I Row Pattern Recognition Overview
+ * ============================================================================
+ *
+ * Row Pattern Recognition (hereafter RPR) is a feature introduced in SQL:2016
+ * that matches regex-based patterns against ordered row sets.
+ *
+ * The SQL standard defines two forms:
+ *
+ * Feature R010: MATCH_RECOGNIZE (FROM clause)
+ * - Dedicated table operator
+ * - Provides dedicated functions such as MATCH_NUMBER(), CLASSIFIER()
+ * - Supports ONE ROW PER MATCH / ALL ROWS PER MATCH
+ *
+ * Feature R020: RPR in a window (WINDOW clause)
+ * - Integrated into the existing window function framework
+ * - Supports ALL ROWS PER MATCH only
+ * - No MATCH_NUMBER()
+ *
+ * This implementation targets Feature R020.
+ *
+ * The basic syntax is as follows:
+ *
+ * SELECT ...
+ * OVER (
+ * PARTITION BY ...
+ * ORDER BY ...
+ * ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING
+ * [INITIAL | SEEK] -- SEEK is defined in the standard but not implemented
+ * AFTER MATCH SKIP TO NEXT ROW | SKIP PAST LAST ROW
+ * PATTERN ( <regex> )
+ * DEFINE <variable> AS <condition>, ...
+ * )
+ *
+ * The PATTERN clause is a regular expression over row pattern variables.
+ * The DEFINE clause specifies boolean conditions that determine whether each
+ * variable evaluates to true for the current row.
+ *
+ * Example:
+ *
+ * PATTERN (A+ B)
+ * DEFINE A AS price > PREV(price),
+ * B AS price < PREV(price)
+ *
+ * This pattern matches "a span where prices rise consecutively then drop."
+ *
+ * Chapter II Overall Processing Pipeline
+ * ============================================================================
+ *
+ * RPR processing is divided into three phases:
+ *
+ * +------------------------------------------------------------+
+ * | 1. Parsing (Parser) |
+ * | SQL text -> PATTERN AST + DEFINE expression tree |
+ * | |
+ * | 2. Compilation (Optimizer/Planner) |
+ * | PATTERN AST -> optimization -> flat NFA element array |
+ * | |
+ * | 3. Execution (Executor) |
+ * | Row-by-row matching via NFA simulation |
+ * +------------------------------------------------------------+
+ *
+ * Each phase uses independent data structures, and the interfaces between
+ * phases are well-defined:
+ *
+ * Parser -> Planner: WindowClause.rpPattern (RPRPatternNode tree)
+ * WindowClause.defineClause (TargetEntry list)
+ *
+ * Planner -> Executor: WindowAgg.rpPattern (RPRPattern struct)
+ * WindowAgg.defineClause (TargetEntry list)
+ *
+ * Chapter III Parsing Phase
+ * ============================================================================
+ *
+ * III-1. Entry Point
+ *
+ * transformWindowDefinitions() (parse_clause.c)
+ * +-- transformRPR() (parse_rpr.c)
+ *
+ * transformRPR() is invoked when RPCommonSyntax is present and performs the
+ * following:
+ *
+ * (1) Frame option validation
+ * - Only ROWS is allowed (RANGE, GROUPS are not)
+ * - The start boundary must be CURRENT ROW
+ * - EXCLUDE option is not allowed
+ *
+ * (2) Transcription to WindowClause
+ * - Copies rpPattern, rpSkipTo, initial fields
+ *
+ * (3) DEFINE clause transformation (transformDefineClause)
+ *
+ * III-2. PATTERN AST
+ *
+ * The parser transforms the PATTERN clause into an RPRPatternNode tree.
+ * Each node has one of the following four types:
+ *
+ * RPR_PATTERN_VAR Variable reference. Name stored in varName field.
+ * RPR_PATTERN_SEQ Concatenation. Children node list in children.
+ * RPR_PATTERN_ALT Alternation. Branch node list in children.
+ * RPR_PATTERN_GROUP Group (parentheses). Body node list in children.
+ *
+ * All nodes have min/max fields to express quantifiers:
+ *
+ * A -> VAR(A, min=1, max=1)
+ * A+ -> VAR(A, min=1, max=INF)
+ * A* -> VAR(A, min=0, max=INF)
+ * A? -> VAR(A, min=0, max=1)
+ * A{3,5} -> VAR(A, min=3, max=5)
+ *
+ * If the reluctant field is true, the quantifier is reluctant (non-greedy).
+ * (RPRPatternNode.reluctant is bool; reluctant_location is the separate
+ * ParseLoc field holding the '?' token position, or -1 if absent.)
+ *
+ * Example: PATTERN ((A+ B) | C*)
+ *
+ * ALT
+ * +-- SEQ
+ * | +-- VAR(A, 1, INF)
+ * | +-- VAR(B, 1, 1)
+ * +-- VAR(C, 0, INF)
+ *
+ * III-3. DEFINE Clause Transformation
+ *
+ * transformDefineClause() processes each DEFINE variable as follows:
+ *
+ * (1) Checks for duplicate variable names
+ * (2) Transforms the expression into a standard SQL expression
+ * (3) Coerces to Boolean type (coerce_to_boolean)
+ * (4) Wraps in a TargetEntry with the variable name set in resname
+ *
+ * Variables that are used in PATTERN but not defined in DEFINE are implicitly
+ * evaluated as TRUE (matching all rows).
+ *
+ * Chapter IV Compilation Phase
+ * ============================================================================
+ *
+ * IV-1. Entry Point
+ *
+ * create_windowagg_plan() (createplan.c)
+ * +-- collectPatternVariables() Collect variable names
+ * +-- filterDefineClause() Remove unused DEFINE entries
+ * +-- buildRPRPattern() NFA compilation (6 phases)
+ *
+ * IV-2. The 6 Phases of buildRPRPattern()
+ *
+ * Phase 1: AST optimization (optimizeRPRPattern)
+ * Phase 2: Statistics collection (scanRPRPattern)
+ * Phase 3: Memory allocation (allocateRPRPattern)
+ * Phase 4: NFA element fill (fillRPRPattern)
+ * Phase 5: Finalization (finalizeRPRPattern)
+ * Phase 6: Absorbability analysis (computeAbsorbability)
+ *
+ * IV-3. Phase 1: AST Optimization
+ *
+ * After copying the parser-generated AST, the following optimizations are
+ * applied:
+ *
+ * (a) SEQ flattening: Unwrap nested SEQ nodes
+ * SEQ(A, SEQ(B, C)) -> SEQ(A, B, C)
+ *
+ * (b) Consecutive variable merging: Merge consecutive occurrences of the
+ * same variable into a single quantifier
+ * A A -> A{2}
+ * A{2,3} A{1,2} -> A{3,5}
+ *
+ * (c) Consecutive group merging: Merge repeated identical groups
+ * (A B)+ (A B)+ -> (A B){2,INF}
+ *
+ * (d) Consecutive ALT merging: Merge repeated identical ALT nodes
+ * (A | B) (A | B) (A | B) -> (A | B){3}
+ *
+ * (e) Prefix/suffix absorption: Absorb identical sequences before/after
+ * a group
+ * A B (A B)+ -> (A B){2,INF}
+ *
+ * (f) ALT flattening and deduplication
+ * (A | (B | C)) -> (A | B | C)
+ * (A | B | A) -> (A | B)
+ *
+ * (g) Quantifier multiplication: Collapse nested quantifiers when safe
+ * (A+)+ -> A+
+ * (A{2,3}){5} -> A{10,15}
+ *
+ * (h) Single-child unwrap
+ * SEQ(A) -> A, (A){1,1} -> A
+ *
+ * IV-4. Phase 4: NFA Element Array Generation
+ *
+ * Transforms the optimized AST into a flat array of RPRPatternElement.
+ * This is the core data structure used for NFA simulation at runtime.
+ *
+ * RPRPatternElement struct (16 bytes):
+ *
+ * Field Size Description
+ * ---------------------------------------------------------
+ * varId 1B Variable ID (0-251) or control code (252-255)
+ * depth 1B Group nesting depth
+ * flags 1B Bit flags (see below)
+ * reserved 1B Padding
+ * min 4B Quantifier lower bound
+ * max 4B Quantifier upper bound
+ * next 2B Next element index (sequential flow)
+ * jump 2B Branch target index (for ALT/GROUP)
+ *
+ * Control codes:
+ *
+ * RPR_VARID_BEGIN (252) Group start marker
+ * RPR_VARID_END (253) Group end marker
+ * RPR_VARID_ALT (254) Alternation start marker
+ * RPR_VARID_FIN (255) Pattern completion marker
+ *
+ * Element flags (1 byte, bitmask):
+ *
+ * 0x01 RPR_ELEM_RELUCTANT (VAR, BEGIN, END)
+ * Non-greedy quantifier. Prefers shorter match: try exit-loop
+ * first, then repeat. Set on VAR for simple (A+?),
+ * on BEGIN+END for group ((...)+?).
+ *
+ * 0x02 RPR_ELEM_EMPTY_LOOP (END)
+ * Group body can produce empty match (all children nullable).
+ * Creates a fast-forward exit clone alongside the normal
+ * loop-back so cycle detection doesn't kill legitimate
+ * matches. (IV-4b)
+ *
+ * 0x04 RPR_ELEM_ABSORBABLE_BRANCH (VAR, BEGIN, END, ALT)
+ * Element lies within an absorbable region. Used at runtime
+ * to track whether the current NFA state is in an absorbable
+ * context.
+ *
+ * 0x08 RPR_ELEM_ABSORBABLE (VAR, END)
+ * Absorption judgment point. Where to compare consecutive
+ * iterations for absorption.
+ * - Simple unbounded VAR (A+): set on the VAR itself
+ * - Unbounded GROUP ((A B)+): set on the END element only
+ *
+ * Accessor macros:
+ * RPRElemIsReluctant(e) (e)->flags & 0x01
+ * RPRElemCanEmptyLoop(e) (e)->flags & 0x02
+ * RPRElemIsAbsorbableBranch(e) (e)->flags & 0x04
+ * RPRElemIsAbsorbable(e) (e)->flags & 0x08
+ *
+ * Example: PATTERN (A+ B | C)
+ *
+ * AST: ALT(SEQ(VAR(A,1,INF), VAR(B,1,1)), VAR(C,1,1))
+ *
+ * Compilation result:
+ *
+ * idx varId depth min max next jump Description
+ * ------------------------------------------------------------
+ * 0 ALT 0 1 1 1 -1 Alternation start
+ * 1 A(0) 1 1 INF 2 3 Branch 1: A+
+ * 2 B(1) 1 1 1 4 -1 Branch 1: B -> FIN
+ * 3 C(2) 1 1 1 4 -1 Branch 2: C -> FIN
+ * 4 FIN 0 1 1 -1 -1 Pattern completion
+ *
+ * - idx 0: ALT marker. next(=1) is the start of the first branch
+ * - idx 1: Variable A. next(=2) is B, jump(=3) is the start of the second
+ * branch
+ * - idx 2: Variable B. next(=4) is FIN
+ * - idx 3: Variable C. next(=4) is FIN
+ * - idx 4: FIN marker. Match completion signal
+ *
+ * Roles of next and jump:
+ *
+ * - next: The next element to move to "after consuming" the current element.
+ * For VAR, the next position after a successful match.
+ * For BEGIN/END, the next position inside/outside the group.
+ *
+ * - jump: The element to "skip to."
+ * In ALT, a jump from one branch to the next branch.
+ * In BEGIN, a skip path to END+1 (for groups with min=0).
+ * In END, a loop-back to the start of the group body.
+ *
+ * Example: PATTERN ((A B)+)
+ *
+ * idx varId depth min max next jump Description
+ * --------------------------------------------------------------
+ * 0 BEGIN 0 1 INF 1 4 Group start
+ * 1 A(0) 1 1 1 2 -1 A
+ * 2 B(1) 1 1 1 3 -1 B
+ * 3 END 0 1 INF 4 1 Group end
+ * 4 FIN 0 1 1 -1 -1 Pattern completion
+ *
+ * - idx 0: BEGIN. next(=1) enters the group body.
+ * jump(=4) skips to after END = FIN (used when min=0).
+ * - idx 3: END. next(=4) exits the group.
+ * jump(=1) loops back to the start of the group body.
+ *
+ * IV-4a. Reluctant Flag (RPR_ELEM_RELUCTANT)
+ *
+ * The reluctant flag is set during Phase 4 (fillRPRPattern) when the AST node
+ * has reluctant == true. It reverses the priority of quantifier expansion at
+ * runtime:
+ *
+ * Greedy (default): try loop-back first, then exit (prefer longer match)
+ * Reluctant: try exit first, then loop-back (prefer shorter match)
+ *
+ * The flag is set on all elements that carry the quantifier:
+ *
+ * Simple VAR (A+?): RPR_ELEM_RELUCTANT on the VAR element
+ * Group ((...)+?): RPR_ELEM_RELUCTANT on BEGIN and END elements
+ *
+ * At runtime (nfa_advance), the flag controls DFS exploration order:
+ *
+ * VAR with quantifier:
+ * Greedy: primary path = next (continue), clone = jump (skip)
+ * Reluctant: primary path = jump (skip), clone = next (continue)
+ *
+ * END element:
+ * Greedy: primary path = jump (loop-back), clone = next (exit)
+ * Reluctant: primary path = next (exit), clone = jump (loop-back)
+ *
+ * BEGIN with min=0:
+ * Greedy: primary path = next (enter group), clone = jump (skip)
+ * Reluctant: primary path = jump (skip), clone = next (enter group)
+ *
+ * The absorption optimization requires greedy quantifiers. Reluctant
+ * quantifiers are excluded from absorbability analysis (see IV-5).
+ *
+ * IV-4b. Empty Loop Flag (RPR_ELEM_EMPTY_LOOP)
+ *
+ * The empty-loop flag is set during Phase 4 (fillRPRPatternGroup) on the END
+ * element when the group body is nullable -- i.e., every path through the
+ * body can match zero rows (all children are nullable).
+ *
+ * Example patterns that trigger this flag:
+ *
+ * (A?)* A is nullable (min=0), so group body is nullable -> END gets flag
+ * (A? B?)+ Both children nullable -> body nullable -> END gets flag
+ * (A | B*) B* is nullable, making the ALT nullable -> END gets flag
+ *
+ * The flag works in conjunction with the empty match cycle detection
+ * (elemIdx visited bitmap). Without this flag, cycle detection alone would
+ * cause legitimate matches to fail.
+ *
+ * Problem example: (A*){2,3}
+ * - Iteration 1: A* consumes all available rows -> count=1, END reached
+ * - Loop-back for iteration 2: A* matches zero rows -> END reached again
+ * - Cycle detection sees the same elemIdx on the same row -> state killed
+ * - count never reaches min(2) -> match fails (incorrect)
+ *
+ * With the RPR_ELEM_EMPTY_LOOP flag, nfa_advance_end creates two paths:
+ * the normal loop-back (which cycle detection will eventually kill) and
+ * a fast-forward exit clone that bypasses the loop entirely.
+ * (See IX-4(c) for detailed runtime behavior.)
+ * - Empty match is impossible since body is not nullable
+ *
+ * IV-5. Absorbability Analysis (RPR_ELEM_ABSORBABLE)
+ *
+ * Context absorption is an optimization technique that reduces O(n^2) to O(n).
+ * (Runtime behavior is described in Chapter VIII.)
+ *
+ * This phase determines whether the pattern has a structure suitable for the
+ * absorption optimization and sets flags on the relevant elements:
+ *
+ * RPR_ELEM_ABSORBABLE Absorption comparison point
+ * RPR_ELEM_ABSORBABLE_BRANCH Element within an absorbable region
+ *
+ * Eligibility conditions:
+ *
+ * (1) SKIP PAST LAST ROW (not NEXT ROW)
+ * (2) Frame end is UNBOUNDED FOLLOWING
+ *
+ * Structural conditions (isUnboundedStart + computeAbsorbabilityRecursive):
+ *
+ * Case 1: Simple VAR+ (e.g., A+)
+ * -> ABSORBABLE | ABSORBABLE_BRANCH set on the VAR
+ * Case 2: GROUP+ whose body consists only of {1,1} VARs (e.g., (A B)+)
+ * -> ABSORBABLE_BRANCH on children,
+ * ABSORBABLE | ABSORBABLE_BRANCH on END
+ * Case 3: GROUP+ whose body starts with VAR+ (e.g., (A+ B)+)
+ * -> Recurses from BEGIN into the body, applying Case 1.
+ * ABSORBABLE | ABSORBABLE_BRANCH set on A.
+ * B and END get no flags -> absorption stops once past A.
+ *
+ * Absorbability is determined per-element, not per-pattern.
+ * Absorption comparison is performed only when a state resides at an
+ * element with the RPR_ELEM_ABSORBABLE flag. Once a state leaves the
+ * flagged region, absorption is permanently disabled for that state.
+ *
+ * Through this mechanism, the runtime guarantees monotonicity:
+ * "a context that started earlier always subsumes a context that
+ * started later."
+ *
+ * Chapter V NFA Runtime Data Structures
+ * ============================================================================
+ *
+ * V-1. RPRNFAState -- NFA State
+ *
+ * A single NFA state represents "how far the pattern has progressed."
+ *
+ * Field Description
+ * -----------------------------------------------------------
+ * elemIdx Index of the current pattern element
+ * counts[] Repetition count per group depth
+ * isAbsorbable Whether the state is in an absorbable region
+ * next Next state in the linked list
+ *
+ * The size of the counts array is rpPattern->maxDepth (= maximum group
+ * nesting depth + 1), allocated as a flexible array member at the end of
+ * the struct.
+ *
+ * Example: In PATTERN ((A B)+ C), a state waiting for B in the 3rd iteration
+ *
+ * Element array: [0:BEGIN(d0) 1:A(d1) 2:B(d1) 3:END(d0) 4:C(d0) 5:FIN]
+ *
+ * elemIdx = 2 (B, depth 1)
+ * counts[0] = 2 (depth 0: depth of END. Group completed 2 iterations)
+ * counts[1] = 1 (depth 1: depth of B. A matched in current iteration)
+ *
+ * Counts are indexed by depth, not by elemIdx.
+ * counts[0] is incremented when passing through END(depth 0),
+ * and the group repetition count is preserved even when
+ * the state is at B(depth 1).
+ *
+ * Definition of two states being "equal":
+ *
+ * Two states are equal if they have the same elemIdx and the same counts
+ * up to the depth of that element.
+ * nfa_states_equal() compares counts[0..elem->depth] using memcmp.
+ * Only counts at or below the depth of the current element are meaningful.
+ *
+ * V-2. RPRNFAContext -- Matching Context
+ *
+ * A single context represents "a matching attempt started from a specific
+ * start row."
+ *
+ * Field Description
+ * ---------------------------------------------------------------------
+ * states Linked list of active NFA states
+ * matchStartRow Row number where matching started
+ * matchEndRow Row number where matching completed
+ * (-1 if incomplete)
+ * lastProcessedRow Last row processed
+ * matchedState State that reached FIN (for greedy fallback)
+ * hasAbsorbableState Whether this context can absorb other contexts
+ * allStatesAbsorbable Whether this context can be absorbed
+ * next, prev Doubly-linked list
+ *
+ * Since the NFA is nondeterministic, multiple states can coexist
+ * simultaneously within a single context.
+ *
+ * Example: In PATTERN (A | B) C, if the first row matches both A and B,
+ * two states coexist within the context:
+ *
+ * State 1: elemIdx=3 (waiting for C, via branch A)
+ * State 2: elemIdx=3 (waiting for C, via branch B)
+ *
+ * In this case, since the (elemIdx, counts) of the two states are equal,
+ * nfa_add_state_unique() retains only State 1 (branch A), which was
+ * added first.
+ * Because DFS processes the first branch of ALT first, the state via A
+ * is registered first, and the state via B is discarded as a duplicate.
+ * This is the preferment guarantee.
+ *
+ * V-3. RPR Fields of WindowAggState
+ *
+ * nfaContext / nfaContextTail Doubly-linked list of active contexts
+ * nfaContextFree Reuse pool for contexts
+ * nfaStateFree Reuse pool for states
+ * nfaVarMatched Per-row cache: varMatched[varId]
+ * nfaVisitedElems Bitmap for cycle detection
+ * nfaStateSize Precomputed size of RPRNFAState
+ *
+ * Memory management:
+ *
+ * States and contexts are managed through their own free lists.
+ * Instead of palloc, they are obtained from the reuse pool, and
+ * returned to the pool upon deallocation.
+ * This reduces the overhead of frequent allocation/deallocation.
+ *
+ * Chapter VI NFA Execution: 3-Phase Model
+ * ============================================================================
+ *
+ * VI-1. Entry Point and Overall Flow
+ *
+ * When the window function processes each row, row_is_in_reduced_frame()
+ * is called. This function determines whether the current row belongs to
+ * a matched frame, and if necessary, calls update_reduced_frame() to
+ * drive the NFA.
+ *
+ * Flow of update_reduced_frame():
+ *
+ * (1) Find or create a context for the target row
+ * (2) Enter the row processing loop
+ * (3) After the loop ends, record the result in reduced_frame_map
+ *
+ * Pseudocode of the row processing loop:
+ *
+ * targetCtx = ExecRPRGetHeadContext(pos)
+ * if targetCtx == NULL:
+ * targetCtx = ExecRPRStartContext(pos)
+ *
+ * for currentPos = startPos; targetCtx->states != NULL; currentPos++:
+ * if not nfa_evaluate_row(currentPos): -- row does not exist
+ * ExecRPRFinalizeAllContexts() -- finalize all contexts
+ * ExecRPRCleanupDeadContexts() -- clean up after finalization
+ * break
+ *
+ * ExecRPRProcessRow(currentPos) -- 3-phase processing
+ * ExecRPRStartContext(currentPos + 1) -- pre-create next start point
+ * ExecRPRCleanupDeadContexts() -- remove dead contexts
+ *
+ * Key point: Processing a single row may require processing multiple rows
+ * ahead. Due to the nature of window functions, determining the frame for
+ * row N requires looking at rows beyond N.
+ *
+ * VI-2. Context Creation: ExecRPRStartContext()
+ *
+ * Creates a new context and performs the initial advance.
+ *
+ * (1) Allocate context via nfa_context_alloc()
+ * (2) Set matchStartRow = pos
+ * (3) Create initial state: elemIdx=0 (first pattern element),
+ * counts=all zero
+ * (4) Call nfa_advance(initialAdvance=true)
+ *
+ * The initial advance expands epsilon transitions at the beginning of
+ * the pattern. For example, the initial advance for PATTERN ((A | B) C):
+ *
+ * Start: elemIdx=0 (ALT)
+ * -> Expand ALT branches
+ * -> elemIdx=1 (A) -- VAR, so add state; stop here
+ * -> elemIdx=2 (B) -- VAR, so add state; stop here
+ *
+ * Result: Two states in the context {waiting for A, waiting for B}
+ *
+ * During the initial advance, reaching FIN is not recorded as a match.
+ * This is to prevent empty matches.
+ *
+ * VI-3. Row Evaluation: nfa_evaluate_row()
+ *
+ * Evaluates all variable conditions in the DEFINE clause at once for
+ * the current row.
+ *
+ * for each defineClause[i]:
+ * result = ExecEvalExpr(defineClause[i])
+ * varMatched[i] = (not null and true)
+ *
+ * To support row navigation operators such as PREV() and NEXT(),
+ * the previous row, current row, and next row are set in separate slots:
+ *
+ * ecxt_scantuple = previous row (for PREV reference)
+ * ecxt_outertuple = current row (default reference)
+ * ecxt_innertuple = next row (for NEXT reference)
+ *
+ * The varMatched array is referenced later in Phase 1 (Match).
+ *
+ * VI-4. ExecRPRProcessRow(): 3-Phase Processing
+ *
+ * NFA processing for a single row is divided into three phases:
+ *
+ * +--------------------------------------------+
+ * | Phase 1: MATCH (convergence) |
+ * | Compare the current row against each VAR |
+ * | state. Remove states that fail to match. |
+ * | |
+ * | Phase 2: ABSORB (absorption) |
+ * | Merge duplicate contexts to prevent |
+ * | state explosion. |
+ * | |
+ * | Phase 3: ADVANCE (expansion) |
+ * | Expand epsilon transitions to prepare |
+ * | for the next row. |
+ * +--------------------------------------------+
+ *
+ * This ordering is important:
+ *
+ * - Match executes first to "consume the current row."
+ * - Absorb executes immediately after Match, when states have been updated.
+ * - Advance executes last to prepare "states waiting for the next row."
+ *
+ * Chapter VII Phase 1: Match
+ * ============================================================================
+ *
+ * nfa_match() iterates through each state in the context:
+ *
+ * (1) Check whether the state's elemIdx is a VAR element
+ * (2) Compare against the current row using nfa_eval_var_match()
+ * (3) Match success: increment repetition count, retain state
+ * (4) Match failure: remove state
+ *
+ * Match determination (nfa_eval_var_match):
+ *
+ * If varId is within the range of defineVariableList:
+ * Use the value of varMatched[varId]
+ *
+ * If varId exceeds the range (variable not defined in DEFINE):
+ * Unconditionally true (matches all rows)
+ *
+ * Immediate advance for simple VARs:
+ *
+ * For a VAR with min=1, max=1 where the next element is END,
+ * the Match phase processes through END immediately.
+ * This is necessary for accurate state comparison in Phase 2 (Absorb).
+ *
+ * Example: In PATTERN ((A B)+), when A matches, it immediately advances
+ * to B, and when B matches, it immediately advances through END to
+ * complete the group count. This enables absorption comparison with
+ * other contexts.
+ *
+ * Chapter VIII Phase 2: Absorb (Context Absorption)
+ * ============================================================================
+ *
+ * VIII-1. Problem
+ *
+ * In the current implementation, a new context is started for each row
+ * processed.
+ * Applying PATTERN (A+) to 10 rows produces 10 contexts,
+ * each of which tracks state independently.
+ *
+ * If there are N rows, the total number of states becomes O(N^2):
+ *
+ * Context 1 (started at row 1): can match A up to N times
+ * Context 2 (started at row 2): can match A up to N-1 times
+ * ...
+ * Context N (started at row N): can match A 1 time
+ *
+ * VIII-2. Solution: Context Absorption
+ *
+ * Key observation: a context started earlier contains
+ * all matches of a later-started context (monotonicity principle).
+ *
+ * If Context 1 started at row 1 and matched A 5 times,
+ * the state where Context 2 (started at row 2) matched A 4 times
+ * is already contained within Context 1.
+ *
+ * Therefore Context 2 can be "absorbed" into Context 1.
+ *
+ * VIII-3. Absorption Conditions
+ *
+ * (1) The pattern is marked as isAbsorbable (see IV-5)
+ * (2) allStatesAbsorbable of the target context is true
+ * (3) An earlier context "covers" all states of the target
+ *
+ * Cover condition (nfa_states_covered):
+ *
+ * A state with the same elemIdx exists in the earlier context,
+ * and the count at that depth is greater than or equal -- then it is covered.
+ *
+ * VIII-4. Dual-Flag Design
+ *
+ * Two boolean flags make the absorption decision efficient:
+ *
+ * hasAbsorbableState (monotonic: only true->false transition possible)
+ * "Does this context have the ability to absorb other contexts?"
+ * true if at least one absorbable state exists.
+ * Transitions to false when states are removed leaving no absorbable
+ * states.
+ * Once false, it never becomes true again.
+ *
+ * allStatesAbsorbable (dynamic: can fluctuate)
+ * "Can this context be absorbed?"
+ * true if all states are in an absorbable region.
+ * Becomes false when a non-absorbable state is added; reverts to true
+ * when it is removed.
+ *
+ * VIII-5. Absorption Order
+ *
+ * nfa_absorb_contexts() traverses from tail (newest) to head (oldest).
+ *
+ * for ctx = tail to head:
+ * if ctx.allStatesAbsorbable:
+ * for older = ctx.prev to head:
+ * if older.hasAbsorbableState:
+ * if nfa_states_covered(older, ctx):
+ * free(ctx) -- absorbed
+ * break
+ *
+ * Since inspection starts from the newest context, the most recently started
+ * (= having the shortest match) context is absorbed first.
+ *
+ * Chapter IX Phase 3: Advance (Epsilon Transition Expansion)
+ * ============================================================================
+ *
+ * IX-1. Overview
+ *
+ * nfa_advance() expands epsilon transitions from each state after Match,
+ * generating "new states waiting for the next row."
+ *
+ * An epsilon transition is a transition that moves without consuming a row:
+ *
+ * - ALT: branch to each alternative
+ * - BEGIN: enter group (or skip if min=0)
+ * - END: loop-back within group (or exit when condition is met)
+ * - FIN: record match completion
+ * - VAR loop/exit: repeat/exit according to the quantifier
+ *
+ * Expansion stops upon reaching a VAR element, and the state is added.
+ * This is because VAR is the element that "will consume the next row."
+ *
+ * IX-2. Processing Order: DFS and Preferment
+ *
+ * advance processes states in lexicographic order,
+ * performing Depth-First Search (DFS) on each state.
+ *
+ * This DFS order is what guarantees the SQL standard's "preferment":
+ *
+ * The branch that appears first in the PATTERN text takes precedence.
+ *
+ * Example: PATTERN (A | B) C
+ *
+ * The first branch A of the ALT takes precedence over the second branch B.
+ * When both A and B can match, the match via A is selected.
+ *
+ * nfa_add_state_unique() prevents duplicate addition of the same state,
+ * so the state added first (= from the preferred branch) is retained.
+ *
+ * IX-3. Routing Function: nfa_route_to_elem()
+ *
+ * All inter-element transitions in the advance phase go through
+ * nfa_route_to_elem().
+ * This function branches its behavior based on the type of the next element:
+ *
+ * If the next element is VAR:
+ * (1) Add the state to the context (nfa_add_state_unique)
+ * (2) If the VAR has min=0, also add a skip path (recurse via next)
+ * -> Expansion stops here (VAR is the element that "will consume the next
+ * row")
+ *
+ * If the next element is non-VAR (ALT, BEGIN, END, FIN):
+ * -> Recursively call nfa_advance_state() to continue expansion
+ *
+ * With this structure, advance recursively follows epsilon transitions
+ * until reaching a VAR, consistently stopping only at VAR elements.
+ *
+ * IX-4. Per-Element advance Behavior
+ *
+ * (a) ALT (nfa_advance_alt)
+ *
+ * Upon encountering an ALT element, all branches are expanded in order.
+ * The first element of each branch is connected via a jump pointer.
+ *
+ * idx=0 (ALT) -> branch 1 start (next) -> branch 2 start (jump) -> ...
+ *
+ * nfa_advance_state() is recursively called for each branch.
+ *
+ * (b) BEGIN (nfa_advance_begin)
+ *
+ * Handles group entry.
+ * jump points to the element after END (= first element outside the group).
+ *
+ * Greedy (default):
+ * (1) Enter the group body (move via next, reset the count at that depth)
+ * (2) If min=0, also add a group skip path (move via jump)
+ *
+ * Reluctant:
+ * Order reversed -- skip path first, group entry second.
+ * If the skip path reaches FIN, the group entry path is not generated
+ * (shortest match preferred).
+ *
+ * (c) END (nfa_advance_end)
+ *
+ * Handles group termination. This is the core of the repetition logic.
+ *
+ * Let count be the count at the current depth:
+ *
+ * count < min:
+ * Loop-back (move via jump, repeat the group body)
+ *
+ * If the RPR_ELEM_EMPTY_LOOP flag is set:
+ * In addition to loop-back, also add a fast-forward exit path.
+ * This is because the body may produce an empty match, causing count
+ * to never reach min. fast-forward resets counts[depth] to 0
+ * and exits via next (treating the remaining required iterations
+ * as empty matches).
+ *
+ * min <= count < max:
+ * Greedy: loop-back first, exit second
+ * Reluctant: exit first, loop-back second
+ * If the exit path reaches FIN, loop-back is omitted.
+ *
+ * count >= max:
+ * Unconditional exit (move via next)
+ *
+ * On exit: reset counts[depth] = 0, and if the next element is an outer END,
+ * increment the count at the outer depth.
+ *
+ * (d) VAR (nfa_advance_var)
+ *
+ * Handles repeat/exit for a VAR element with a quantifier.
+ *
+ * Let count be the count at the current depth:
+ *
+ * count < min:
+ * Unconditional loop (stay at the same elemIdx, wait for the next row)
+ *
+ * min <= count < max:
+ * Greedy: loop first, exit (next) second
+ * Reluctant: exit first, loop second
+ * If the exit path reaches FIN, loop is omitted.
+ *
+ * count >= max:
+ * Unconditional exit (move via next)
+ *
+ * On exit: reset counts[depth] = 0.
+ *
+ * (e) FIN
+ *
+ * Match success. The current state is moved to matchedState for recording,
+ * and matchEndRow is set to the current row.
+ *
+ * Upon reaching FIN, all remaining unprocessed states are removed
+ * (early termination). By DFS order, the path that reached FIN first
+ * has the highest preferment, so the rest are inferior paths.
+ * This is the core mechanism that guarantees preferment.
+ *
+ * In SKIP PAST LAST ROW mode, upon reaching FIN, subsequent contexts
+ * that started within the match range are immediately pruned.
+ *
+ * IX-5. State Deduplication: nfa_add_state_unique()
+ *
+ * When adding a new state to a context, it is compared against existing
+ * states;
+ * if an identical state already exists, it is not added.
+ *
+ * Comparison criteria: elemIdx + counts[0..elem->depth] (see V-1)
+ *
+ * This deduplication is the core mechanism that suppresses NFA state
+ * explosion.
+ * Because DFS order causes preferred-branch states to be added first,
+ * identical states from lower-priority branches are automatically discarded.
+ *
+ * IX-6. Cycle Detection: nfaVisitedElems
+ *
+ * When a group body can produce an empty match,
+ * looping back from END may cause an infinite loop.
+ *
+ * Example: PATTERN ((A?)*)
+ *
+ * A? has min=0, so it can pass through without matching.
+ * If the outer group repeats: BEGIN -> A? skip -> END -> BEGIN -> ...
+ *
+ * To prevent this:
+ *
+ * (1) At compile time: set the RPR_ELEM_EMPTY_LOOP flag on the END
+ * of groups whose body is nullable.
+ * The runtime effect of this flag is described in IX-4(c):
+ * when count < min, a fast-forward exit path is added,
+ * resolving the deadlock where count cannot increase due to empty
+ * matches.
+ *
+ * (2) At runtime: initialize the nfaVisitedElems bitmap immediately before
+ * DFS expansion of each state within advance (once per state).
+ * During DFS, set the corresponding elemIdx bit when visiting each
+ * element.
+ * If a previously visited elemIdx is revisited, that path is terminated.
+ *
+ * Note: the bitmap tracks only elemIdx and does not consider counts.
+ * Therefore, legitimate revisits to the same elemIdx but with different
+ * counts may also be blocked. This only occurs when the group body is
+ * nullable (all paths can match empty), causing END -> loop-back ->
+ * skip -> END within a single DFS. In such cases the END element has
+ * the RPR_ELEM_EMPTY_LOOP flag, so the fast-forward exit (IX-4(c))
+ * provides an alternative path that bypasses the cycle.
+ *
+ * Chapter X Match Result Processing
+ * ============================================================================
+ *
+ * X-1. Reduced Frame Map
+ *
+ * RPR match results are recorded in a byte array called reduced_frame_map.
+ * One byte is allocated per row, and the value is one of the following:
+ *
+ * RF_NOT_DETERMINED (0) Not yet processed
+ * RF_FRAME_HEAD (1) Start row of the match
+ * RF_SKIPPED (2) Interior row of the match (skipped in frame)
+ * RF_UNMATCHED (3) Match failure
+ *
+ * The window function references this map to determine frame inclusion for
+ * each row.
+ *
+ * X-2. AFTER MATCH SKIP
+ *
+ * Determines the starting point for the next match attempt after a successful
+ * match:
+ *
+ * SKIP TO NEXT ROW:
+ * New match attempt begins from the row after the match start row.
+ * Overlapping matches are possible.
+ *
+ * SKIP PAST LAST ROW:
+ * New match attempt begins from the row after the match end row.
+ * Only non-overlapping matches are possible.
+ *
+ * X-3. INITIAL vs SEEK
+ *
+ * Standard definition (section 6.12):
+ * INITIAL: "is used to look for a match whose first row is R."
+ * SEEK: "is used to permit a search for the first match anywhere
+ * from R through the end of the full window frame."
+ * In either case, if there is no match, the reduced window frame is empty.
+ * The default is INITIAL.
+ *
+ * Current implementation:
+ * SEEK is not supported (the parser raises an error).
+ * Only INITIAL is supported, searching only for matches starting at each
+ * row position pos.
+ *
+ * Chapter XI Worked Example: Full Execution Trace
+ * ============================================================================
+ *
+ * XI-1. Query
+ *
+ * SELECT company, tdate, price,
+ * first_value(price) OVER w AS start_price,
+ * last_value(price) OVER w AS end_price
+ * FROM stock
+ * WINDOW w AS (
+ * PARTITION BY company
+ * ORDER BY tdate
+ * ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING
+ * AFTER MATCH SKIP PAST LAST ROW
+ * PATTERN (A+ B)
+ * DEFINE A AS price > PREV(price),
+ * B AS price < PREV(price)
+ * );
+ *
+ * XI-2. Data
+ *
+ * Row# tdate price
+ * --------------------------
+ * 0 2024-01-01 100
+ * 1 2024-01-02 110
+ * 2 2024-01-03 120
+ * 3 2024-01-04 115
+ * 4 2024-01-05 130
+ *
+ * XI-3. Compilation Result
+ *
+ * PATTERN (A+ B) -> unchanged after optimization
+ *
+ * idx varId depth min max next jump
+ * -----------------------------------------
+ * 0 A(0) 0 1 INF 1 -1 A+
+ * 1 B(1) 0 1 1 2 -1 B
+ * 2 FIN 0 1 1 -1 -1
+ *
+ * DEFINE: A -> "price > PREV(price)", B -> "price < PREV(price)"
+ * isAbsorbable = true (A+ is a simple unbounded VAR)
+ *
+ * XI-4. Execution Trace
+ *
+ * --- Row 0 (price=100) ---
+ *
+ * update_reduced_frame(0) called.
+ *
+ * Context C0 created (matchStartRow=0).
+ * Initial advance: elemIdx=0(A) -> VAR, so state is added.
+ * C0.states = [{elemIdx=0, counts=[0]}]
+ *
+ * nfa_evaluate_row(0):
+ * A: price(100) > PREV(price) -> no PREV -> false
+ * B: price(100) < PREV(price) -> no PREV -> false
+ * varMatched = [false, false]
+ *
+ * ExecRPRProcessRow(0):
+ * Phase 1 (Match): A(0) state vs varMatched[0]=false -> state removed
+ * C0.states = [] (empty)
+ *
+ * Phase 2 (Absorb): skipped (no states)
+ * Phase 3 (Advance): skipped (no states)
+ *
+ * C0.states is empty, so the loop terminates.
+ * matchEndRow < matchStartRow -> RF_UNMATCHED.
+ * register_reduced_frame_map(0, RF_UNMATCHED).
+ *
+ * --- Row 1 (price=110) ---
+ *
+ * update_reduced_frame(1) called.
+ *
+ * Context C1 created (matchStartRow=1).
+ * Initial advance: C1.states = [{elemIdx=0, counts=[0]}]
+ *
+ * nfa_evaluate_row(1):
+ * A: 110 > PREV(100) -> true
+ * B: 110 < PREV(100) -> false
+ * varMatched = [true, false]
+ *
+ * ExecRPRProcessRow(1):
+ * Phase 1 (Match): A(0) match succeeds -> counts[0]++ -> counts=[1]
+ * C1.states = [{elemIdx=0, counts=[1]}]
+ *
+ * Phase 3 (Advance):
+ * State {elemIdx=0, counts=[1]}: A+ (min=1, count=1, max=INF)
+ * count >= min, so:
+ * Greedy -> loop first: keep {elemIdx=0, counts=[1]}
+ * exit: reset counts[0]=0, next(=1) -> {elemIdx=1,
+ * counts=[0]}
+ * C1.states = [{elemIdx=0, counts=[1]}, {elemIdx=1, counts=[0]}]
+ *
+ * --- Row 2 (price=120) ---
+ *
+ * Context C2 created (matchStartRow=2).
+ * Initial advance: C2.states = [{elemIdx=0, counts=[0]}]
+ *
+ * nfa_evaluate_row(2):
+ * A: 120 > PREV(110) -> true
+ * B: 120 < PREV(110) -> false
+ * varMatched = [true, false]
+ *
+ * C1 ExecRPRProcessRow(2):
+ * Phase 1 (Match):
+ * {elemIdx=0, counts=[1]}: A matches -> counts=[2]
+ * {elemIdx=1, counts=[0]}: B does not match -> removed
+ * C1.states = [{elemIdx=0, counts=[2]}]
+ *
+ * C2 ExecRPRProcessRow(2):
+ * Phase 1 (Match):
+ * {elemIdx=0, counts=[0]}: A matches -> counts=[1]
+ * C2.states = [{elemIdx=0, counts=[1]}]
+ *
+ * Phase 2 (Absorb):
+ * Does C1 (started earlier) cover C2?
+ * C1: {elemIdx=0, counts=[2]}, C2: {elemIdx=0, counts=[1]}
+ * Same elemIdx, C1.counts >= C2.counts -> covered
+ * C2 absorbed. -> removed.
+ *
+ * Phase 3 (Advance):
+ * {elemIdx=0, counts=[2]}: Greedy -> loop + exit
+ * Loop: {elemIdx=0, counts=[2]}
+ * Exit: reset counts[0]=0, next(=1) -> {elemIdx=1, counts=[0]}
+ * C1.states = [{elemIdx=0, counts=[2]}, {elemIdx=1, counts=[0]}]
+ *
+ * Context C3 created (matchStartRow=3).
+ *
+ * --- Row 3 (price=115) ---
+ *
+ * nfa_evaluate_row(3):
+ * A: 115 > PREV(120) -> false
+ * B: 115 < PREV(120) -> true
+ * varMatched = [false, true]
+ *
+ * ExecRPRProcessRow(3):
+ * Phase 1 (Match):
+ * {elemIdx=0, counts=[2]}: A does not match -> removed
+ * {elemIdx=1, counts=[0]}: B matches -> counts=[1]
+ * C1.states = [{elemIdx=1, counts=[1]}]
+ *
+ * Phase 3 (Advance):
+ * {elemIdx=1, counts=[1]}: B (min=1, max=1)
+ * count(1) >= max(1) -> unconditional exit
+ * Reset counts[0]=0, next = 2 (FIN)
+ * FIN reached -> matchEndRow = 3, matchedState recorded.
+ * Early termination: no remaining states, so completed immediately.
+ * C1.states = [] (empty after reaching FIN)
+ *
+ * C1.states is empty and matchEndRow=3 >= matchStartRow=1 -> match succeeds.
+ *
+ * register_reduced_frame_map(1, RF_FRAME_HEAD)
+ * register_reduced_frame_map(2, RF_SKIPPED)
+ * register_reduced_frame_map(3, RF_SKIPPED)
+ *
+ * --- Row 4 (price=130) ---
+ *
+ * update_reduced_frame(4) called.
+ * C3 was already created but matchStartRow=3, so it is not applicable.
+ * New context C4 created (matchStartRow=4).
+ *
+ * nfa_evaluate_row(4):
+ * A: 130 > PREV(115) -> true
+ * B: 130 < PREV(115) -> false
+ *
+ * ... No subsequent rows, so ExecRPRFinalizeAllContexts() is called.
+ * Match incomplete -> RF_UNMATCHED.
+ *
+ * XI-5. Final Result
+ *
+ * Row 0: RF_UNMATCHED -> frame = the row itself
+ * Row 1: RF_FRAME_HEAD -> frame = rows 1 through 3
+ * Row 2: RF_SKIPPED -> inside row 1's match
+ * Row 3: RF_SKIPPED -> inside row 1's match
+ * Row 4: RF_UNMATCHED -> frame = the row itself
+ *
+ * Chapter XII Summary of Key Design Decisions
+ * ============================================================================
+ *
+ * XII-1. Flat Array vs Tree-Based NFA
+ *
+ * Choice: Flat array (RPRPatternElement[])
+ *
+ * Rationale:
+ * - Cache-friendly: 16-byte fixed size, contiguous memory
+ * - Index-based references: 2-byte indices instead of pointers
+ * - Easy to serialize: can use memcpy when passing to plan nodes
+ *
+ * XII-2. Forward-only Execution vs Backtracking
+ *
+ * Choice: Forward-only (state set tracking)
+ *
+ * Rationale:
+ * - Backtracking takes exponential time in the worst case
+ * - NFA simulation guarantees polynomial time
+ * - DFS order naturally guarantees preferment.
+ * Greedy/reluctant per quantifier requires only reversing the DFS order
+ * - Window functions receive sorted rows sequentially.
+ * Forward-only fits directly into this pipeline,
+ * whereas backtracking requires re-fetching previous rows
+ * - DEFINE conditions are SQL expressions (PREV, RUNNING aggregates, etc.)
+ * with high re-evaluation cost. Forward-only requires only one evaluation
+ * per row
+ *
+ * XII-3. Per-Context Management
+ *
+ * Choice: Independent context per start row
+ *
+ * Rationale:
+ * - Supports overlapping matches under SKIP TO NEXT ROW
+ * - Determines the frame for each row independently
+ * - Absorption optimization can eliminate redundant contexts in O(n)
+ *
+ * XII-4. Memory Pool Management
+ *
+ * Choice: Custom free list
+ *
+ * Rationale:
+ * - NFA states are created and destroyed in large numbers per row
+ * - Avoids palloc/pfree overhead
+ * - State size is variable (counts[] array), but within a single query
+ * maxDepth is fixed, so all states have the same size
+ *
+ * XII-5. Execution Optimization Summary
+ *
+ * The following optimizations make the NFA simulation practical.
+ *
+ * -- Compile-time --
+ *
+ * (1) AST Optimization (IV-3)
+ *
+ * Simplifies the AST before converting the pattern to an NFA.
+ * Reduces the number of NFA elements through consecutive variable
+ * merging (A A -> A{2}), SEQ flattening, quantifier multiplication,
+ * and other transformations.
+ *
+ * Significance: Reducing the element count directly shrinks the state
+ * space, decreasing the cost of all subsequent runtime phases (match,
+ * absorb, advance).
+ *
+ * -- Runtime: advance phase --
+ *
+ * (2) Group Skip (IX-4(b))
+ *
+ * At the BEGIN of a group with min=0, uses jump to skip the entire
+ * group. Moves directly to the first element outside the group without
+ * exploring the group body. Greedy enters then skips; Reluctant skips
+ * then enters.
+ *
+ * Significance: For optional groups (min=0), immediately generates
+ * a skip path without exploring the body, avoiding unnecessary DFS
+ * expansion.
+ *
+ * (3) State Deduplication (IX-5)
+ *
+ * During advance, DFS may generate states with the same (elemIdx,
+ * counts) combination through multiple paths. Additionally, unlike
+ * VAR repetition, group repetition cannot perform absorption
+ * comparison using VAR states, so inline advance is performed from
+ * after Phase 1 match through to END; this process can also produce
+ * duplicate states reaching the same END.
+ * nfa_add_state_unique() blocks duplicate addition of identical states
+ * in both cases.
+ *
+ * Significance: Prevents exponential growth of the state count in
+ * ALT branches and quantifier expansion. Since DFS order causes the
+ * preferred branch's state to be registered first, identical states
+ * from lower-priority branches are automatically discarded, thereby
+ * also guaranteeing preferment.
+ *
+ * (4) Cycle Detection and Fast-Forward (IX-6, IX-4(c))
+ *
+ * When a nullable group body (e.g., A?) repeats empty matches,
+ * the END -> BEGIN loop-back can continue indefinitely.
+ *
+ * Two mechanisms resolve this:
+ * - A visited bitmap (nfaVisitedElems) blocks revisitation of the
+ * same element, preventing infinite loops (safety)
+ * - At an END with the RPR_ELEM_EMPTY_LOOP flag set, when
+ * count < min, the remaining required iterations are treated as
+ * empty matches and a fast-forward exit path out of the group is
+ * added (correctness)
+ *
+ * Significance: Cycle detection guarantees termination, and
+ * fast-forward guarantees that the min condition is satisfied.
+ * Without these, patterns containing nullable groups would fall
+ * into infinite loops or fail to match.
+ *
+ * (5) Match Pruning (IX-4(e))
+ *
+ * When a state reaches FIN during advance, all remaining unprocessed
+ * states of that context are removed. Because of DFS order, the path
+ * that reaches FIN first has the highest preferment, so the remaining
+ * paths are inferior.
+ *
+ * Significance: Once the best match is determined, exploration of
+ * inferior paths is immediately terminated. This mechanism achieves
+ * both preferment guarantees and performance optimization.
+ *
+ * -- Runtime: inter-context --
+ *
+ * (6) Early Termination (SKIP PAST LAST ROW)
+ *
+ * In SKIP PAST LAST ROW mode, when a match is found, subsequent
+ * contexts whose start rows fall within the match range are pruned
+ * immediately without further processing.
+ * In SKIP TO NEXT ROW mode, overlapping contexts are preserved
+ * because each row requires its own independent match.
+ *
+ * Significance: Prunes subsequent contexts whose start rows overlap
+ * with a prior match range, avoiding unnecessary processing.
+ *
+ * (7) Context Absorption (Chapter VIII)
+ *
+ * If an independent context is created for each row, O(n^2) states
+ * accumulate. By exploiting the monotonicity that an earlier-started
+ * context subsumes the states of a later-started context, redundant
+ * contexts are eliminated early.
+ *
+ * Absorbability is determined per-element; comparison is performed
+ * only at elements with the RPR_ELEM_ABSORBABLE flag (see IV-5).
+ *
+ * Significance: Keeps the number of active contexts at a constant
+ * level, achieving O(n^2) -> O(n) time complexity. Without this,
+ * performance degrades sharply on long partitions.
+ *
+ * Appendix A. Key Function Index
+ * ============================================================================
+ *
+ * Function File Role
+ * --------------------------------------------------------------------------
+ * transformRPR parse_rpr.c Parser entry point
+ * transformDefineClause parse_rpr.c DEFINE transformation
+ * collectPatternVariables rpr.c Variable collection
+ * filterDefineClause rpr.c DEFINE filtering
+ * buildRPRPattern rpr.c NFA compilation main
+ * optimizeRPRPattern rpr.c AST optimization
+ * fillRPRPattern rpr.c NFA element generation
+ * finalizeRPRPattern rpr.c Finalization
+ * computeAbsorbability rpr.c Absorption analysis
+ * update_reduced_frame nodeWindowAgg.c Execution main loop
+ * nfa_evaluate_row nodeWindowAgg.c DEFINE evaluation
+ * ExecRPRStartContext execRPR.c Context creation
+ * ExecRPRProcessRow execRPR.c 3-phase processing
+ * nfa_match execRPR.c Phase 1
+ * nfa_absorb_contexts execRPR.c Phase 2
+ * nfa_advance execRPR.c Phase 3
+ * nfa_advance_state execRPR.c Per-state branching
+ * nfa_route_to_elem execRPR.c Element routing
+ * nfa_advance_alt execRPR.c ALT handling
+ * nfa_advance_begin execRPR.c BEGIN handling
+ * nfa_advance_end execRPR.c END handling
+ * nfa_advance_var execRPR.c VAR handling
+ * nfa_add_state_unique execRPR.c Deduplication
+ * nfa_states_covered execRPR.c Absorption check
+ *
+ * Appendix B. Data Structure Relationship Diagram
+ * ============================================================================
+ *
+ * Parser Layer
+ * --------
+ * RPCommonSyntax
+ * |--- rpSkipTo: RPSkipTo
+ * |--- initial: bool
+ * +--- rpPattern: RPRPatternNode* (tree)
+ * |--- nodeType: VAR | SEQ | ALT | GROUP
+ * |--- min, max: quantifier
+ * |--- varName: variable name (VAR only)
+ * +--- children: List* (SEQ/ALT/GROUP only)
+ *
+ * Planner Layer
+ * ----------
+ * WindowAgg (plan node)
+ * |--- rpSkipTo: RPSkipTo
+ * |--- defineClause: List<TargetEntry>
+ * +--- rpPattern: RPRPattern*
+ * |--- numVars: int
+ * |--- varNames: char**
+ * |--- maxDepth: RPRDepth
+ * |--- isAbsorbable: bool
+ * |--- numElements: int
+ * +--- elements: RPRPatternElement[] (flat array)
+ * |--- varId (1B)
+ * |--- depth (1B)
+ * |--- flags (1B)
+ * |--- reserved (1B)
+ * |--- min, max (4B + 4B)
+ * +--- next, jump (2B + 2B)
+ *
+ * Executor Layer
+ * ----------
+ * WindowAggState
+ * |--- rpSkipTo: RPSkipTo (AFTER MATCH SKIP mode)
+ * |--- rpPattern: RPRPattern* (copied from plan)
+ * |--- defineVariableList: List<String> (variable names, DEFINE order)
+ * |--- defineClauseList: List<ExprState>
+ * |--- nfaVarMatched: bool[] (per-row cache)
+ * |--- nfaVisitedElems: bitmapword* (cycle detection)
+ * |--- nfaStateSize: Size (pre-calculated RPRNFAState allocation size)
+ * |--- nfaContext <-> nfaContextTail (doubly-linked list)
+ * | +--- RPRNFAContext
+ * | |--- states: RPRNFAState* (linked list)
+ * | | |--- elemIdx
+ * | | |--- counts[]
+ * | | +--- isAbsorbable
+ * | |--- matchStartRow, matchEndRow
+ * | |--- lastProcessedRow
+ * | |--- matchedState (cloned on FIN arrival)
+ * | |--- hasAbsorbableState
+ * | +--- allStatesAbsorbable
+ * |--- nfaContextFree (recycling pool)
+ * +--- nfaStateFree (recycling pool)
+ *
+ * Appendix C. NFA Element Array Examples
+ * ============================================================================
+ *
+ * C-1. PATTERN (A B C)
+ *
+ * idx varId depth min max next jump
+ * ------------------------------------------
+ * 0 A 0 1 1 1 -1
+ * 1 B 0 1 1 2 -1
+ * 2 C 0 1 1 3 -1
+ * 3 FIN 0 1 1 -1 -1
+ *
+ * C-2. PATTERN (A+ B*)
+ *
+ * idx varId depth min max next jump flags
+ * ------------------------------------------------------------------------
+ * 0 A 0 1 INF 1 -1 ABSORBABLE | ABSORBABLE_BRANCH
+ * 1 B 0 0 INF 2 -1
+ * 2 FIN 0 1 1 -1 -1
+ *
+ * Only A+ is the absorption point (Case 1). Once past A,
+ * absorption is permanently disabled for that state.
+ *
+ * C-3. PATTERN (A | B | C)
+ *
+ * idx varId depth min max next jump
+ * ----------------------------------------
+ * 0 ALT 0 1 1 1 -1 alternation start
+ * 1 A 1 1 1 4 2 branch 1 -> FIN, jump -> branch 2
+ * 2 B 1 1 1 4 3 branch 2 -> FIN, jump -> branch 3
+ * 3 C 1 1 1 4 -1 branch 3 -> FIN
+ * 4 FIN 0 1 1 -1 -1
+ *
+ * C-4. PATTERN ((A B)+ C)
+ *
+ * idx varId depth min max next jump flags
+ * --------------------------------------------------------------------------
+ * 0 BEGIN 0 1 INF 1 4 ABSORBABLE_BRANCH
+ * 1 A 1 1 1 2 -1 ABSORBABLE_BRANCH
+ * 2 B 1 1 1 3 -1 ABSORBABLE_BRANCH
+ * 3 END 0 1 INF 4 1 ABSORBABLE | ABSORBABLE_BRANCH
+ * 4 C 0 1 1 5 -1
+ * 5 FIN 0 1 1 -1 -1
+ *
+ * Case 2: GROUP+ with {1,1} body VARs. A, B are branches;
+ * END is the absorption point. Compare with C-6 (Case 3).
+ *
+ * C-5. PATTERN ((A | B)+? C)
+ *
+ * idx varId depth min max next jump flags
+ * -------------------------------------------------------------------
+ * 0 BEGIN 0 1 INF 1 5 RELUCTANT, group start
+ * 1 ALT 1 1 1 2 -1 alternation start
+ * 2 A 2 1 1 4 3 branch 1
+ * 3 B 2 1 1 4 -1 branch 2
+ * 4 END 0 1 INF 5 1 RELUCTANT, group end
+ * 5 C 0 1 1 6 -1
+ * 6 FIN 0 1 1 -1 -1
+ *
+ * C-6. PATTERN ((A+ B)+ C) -- Absorbability flag example
+ *
+ * idx varId depth min max next jump flags
+ * ---------------------------------------------------------------------------
+ * 0 BEGIN 0 1 INF 1 4 ABSORBABLE_BRANCH, group start
+ * 1 A 1 1 INF 2 -1 ABSORBABLE | ABSORBABLE_BRANCH
+ * 2 B 1 1 1 3 -1
+ * 3 END 0 1 INF 4 1 group end
+ * 4 C 0 1 1 5 -1
+ * 5 FIN 0 1 1 -1 -1
+ *
+ * Recurses from BEGIN into the body -> A matches Case 1 (simple VAR+).
+ * A gets ABSORBABLE | ABSORBABLE_BRANCH, BEGIN gets ABSORBABLE_BRANCH.
+ * B and END get no flags -> absorption stops once the state advances to B.
+ * (See IV-5 Case 3)
+ *
+ * C-7. PATTERN ((A+ B | C*)+ D) -- Per-branch absorption in ALT
+ *
+ * idx varId depth min max next jump flags
+ * ---------------------------------------------------------------------------
+ * 0 BEGIN 0 1 INF 1 6 ABSORBABLE_BRANCH
+ * 1 ALT 1 1 1 2 -1 ABSORBABLE_BRANCH
+ * 2 A 2 1 INF 3 4 ABSORBABLE | ABSORBABLE_BRANCH
+ * 3 B 2 1 1 5 -1
+ * 4 C 2 0 INF 5 -1 ABSORBABLE | ABSORBABLE_BRANCH
+ * 5 END 0 1 INF 6 1 EMPTY_LOOP
+ * 6 D 0 1 1 7 -1
+ * 7 FIN 0 1 1 -1 -1
+ *
+ * ALT branches are checked independently for absorbability.
+ * Branch 1: A+ matches Case 1 -> A gets ABSORBABLE. B has no flag.
+ * Branch 2: C* matches Case 1 -> C gets ABSORBABLE.
+ * Both A and C get ABSORBABLE_BRANCH as part of their respective branch
+ * paths.
+ * END has EMPTY_LOOP: branch 2 (C*) is nullable, making the group body
+ * nullable.
+ * BEGIN and ALT get ABSORBABLE_BRANCH (on the path to absorbable elements).
+ *
+ * ============================================================================
+ * End of document
+ * ============================================================================
+ */
+
+/* Bitmap macros for NFA cycle detection (cf. bitmapset.c, tidbitmap.c) */
+#define WORDNUM(x) ((x) / BITS_PER_BITMAPWORD)
+#define BITNUM(x) ((x) % BITS_PER_BITMAPWORD)
+
+/* Forward declarations - NFA state management */
+static RPRNFAState *nfa_state_alloc(WindowAggState *winstate);
+static void nfa_state_free(WindowAggState *winstate, RPRNFAState *state);
+static void nfa_state_free_list(WindowAggState *winstate, RPRNFAState *list);
+static RPRNFAState *nfa_state_create(WindowAggState *winstate, int16 elemIdx,
+ int32 *counts, bool sourceAbsorbable);
+static bool nfa_states_equal(WindowAggState *winstate, RPRNFAState *s1,
+ RPRNFAState *s2);
+static bool nfa_add_state_unique(WindowAggState *winstate, RPRNFAContext *ctx,
+ RPRNFAState *state);
+static void nfa_add_matched_state(WindowAggState *winstate, RPRNFAContext *ctx,
+ RPRNFAState *state, int64 matchEndRow);
+
+/* Forward declarations - NFA context management (internal) */
+static RPRNFAContext *nfa_context_alloc(WindowAggState *winstate);
+static void nfa_unlink_context(WindowAggState *winstate, RPRNFAContext *ctx);
+
+/* Forward declarations - NFA statistics */
+static void nfa_update_length_stats(int64 count, NFALengthStats *stats, int64 newLen);
+static void nfa_record_context_skipped(WindowAggState *winstate, int64 skippedLen);
+static void nfa_record_context_absorbed(WindowAggState *winstate, int64 absorbedLen);
+
+/* Forward declarations - NFA absorption */
+static void nfa_update_absorption_flags(RPRNFAContext *ctx);
+static bool nfa_states_covered(RPRPattern *pattern, RPRNFAContext *older,
+ RPRNFAContext *newer);
+static void nfa_try_absorb_context(WindowAggState *winstate, RPRNFAContext *ctx);
+static void nfa_absorb_contexts(WindowAggState *winstate);
+
+/* Forward declarations - NFA match and advance */
+static bool nfa_eval_var_match(WindowAggState *winstate,
+ RPRPatternElement *elem, bool *varMatched);
+static void nfa_match(WindowAggState *winstate, RPRNFAContext *ctx,
+ bool *varMatched);
+static void nfa_advance_state(WindowAggState *winstate, RPRNFAContext *ctx,
+ RPRNFAState *state, int64 currentPos);
+static void nfa_route_to_elem(WindowAggState *winstate, RPRNFAContext *ctx,
+ RPRNFAState *state, RPRPatternElement *nextElem,
+ int64 currentPos);
+static void nfa_advance_alt(WindowAggState *winstate, RPRNFAContext *ctx,
+ RPRNFAState *state, RPRPatternElement *elem,
+ int64 currentPos);
+static void nfa_advance_begin(WindowAggState *winstate, RPRNFAContext *ctx,
+ RPRNFAState *state, RPRPatternElement *elem,
+ int64 currentPos);
+static void nfa_advance_end(WindowAggState *winstate, RPRNFAContext *ctx,
+ RPRNFAState *state, RPRPatternElement *elem,
+ int64 currentPos);
+static void nfa_advance_var(WindowAggState *winstate, RPRNFAContext *ctx,
+ RPRNFAState *state, RPRPatternElement *elem,
+ int64 currentPos);
+static void nfa_advance(WindowAggState *winstate, RPRNFAContext *ctx,
+ int64 currentPos);
+
+/*
+ * NFA-based pattern matching implementation
+ *
+ * These functions implement direct NFA execution using the compiled
+ * RPRPattern structure, avoiding regex compilation overhead.
+ *
+ * Execution Flow: match -> absorb -> advance
+ * -----------------------------------------
+ * The NFA execution follows a three-phase cycle for each row:
+ *
+ * 1. MATCH (convergence): Evaluate all waiting states against current row.
+ * States on VAR elements are checked against their defining conditions.
+ * Failed matches are removed, successful ones may transition forward.
+ * This is a "convergence" phase - the number of states tends to decrease.
+ *
+ * 2. ABSORB: After matching, check if any context can absorb another.
+ * Context absorption is an optimization that merges equivalent contexts.
+ * A context can only be absorbed if ALL its states are absorbable.
+ *
+ * 3. ADVANCE (divergence): Expand states through epsilon transitions.
+ * States advance through ALT (alternation), END (group end), and
+ * optional elements until reaching VAR or FIN elements where they wait.
+ * This is a "divergence" phase - ALT creates multiple branch states.
+ *
+ * Key Design Decisions:
+ * ---------------------
+ * - VAR->END transition in match phase: When a simple VAR (max=1) matches
+ * and the next element is END, we transition immediately in the match
+ * phase rather than waiting for advance. This is necessary for correct
+ * absorption: states must be at END to be marked absorbable before the
+ * absorption check occurs.
+ *
+ * - Optional VAR skip paths: When advance lands on a VAR with min=0,
+ * we create both a waiting state AND a skip state (like ALT branches).
+ * This ensures patterns like "A B? C" work correctly - we need a state
+ * waiting for B AND a state that has already skipped to C.
+ *
+ * - END->END count increment: When transitioning from one END to another
+ * END within advance, we must increment the outer END's count. This
+ * handles nested groups like "((A|B)+)+" correctly - exiting the inner
+ * group counts as one iteration of the outer group.
+ *
+ * - Empty match handling: The initial advance uses currentPos =
+ * startPos - 1 (before any row is consumed). If FIN is reached via
+ * epsilon transitions alone, matchEndRow = startPos - 1 < matchStartRow,
+ * resulting in UNMATCHED. For reluctant min=0 patterns (A*?, A??),
+ * the skip path reaches FIN first and early termination prunes enter
+ * paths, yielding an immediate empty (unmatched) result. For
+ * greedy patterns (A*), the enter path adds VAR states first, then
+ * the skip FIN is recorded but VAR states survive for later matching.
+ *
+ * Context Absorption Runtime:
+ * ---------------------------
+ * Absorption uses flags computed at planning time (in rpr.c) and two
+ * context-level flags maintained at runtime:
+ *
+ * State-level:
+ * state.isAbsorbable: true if state is in the absorbable region.
+ * - Set at creation: elem->flags & RPR_ELEM_ABSORBABLE_BRANCH
+ * - At transition: prevAbsorbable && (newElem->flags & ABSORBABLE_BRANCH)
+ * - Monotonic: once false, stays false forever
+ *
+ * Context-level:
+ * ctx.hasAbsorbableState: can this context absorb others?
+ * - True if at least one state has isAbsorbable=true
+ * - Monotonic: true->false only (optimization: skip recalc when false)
+ *
+ * ctx.allStatesAbsorbable: can this context be absorbed?
+ * - True if ALL states have isAbsorbable=true
+ * - Dynamic: can change false->true (when non-absorbable states die)
+ *
+ * Absorption Algorithm:
+ * For each pair (older Ctx1, newer Ctx2):
+ * 1. Pre-check: Ctx1.hasAbsorbableState && Ctx2.allStatesAbsorbable
+ * -> If false, skip (fast filter)
+ * 2. Coverage check: For each Ctx2 state with isAbsorbable=true,
+ * find Ctx1 state with same elemIdx and count >= Ctx2.count
+ * 3. If all Ctx2 absorbable states are covered, absorb Ctx2
+ *
+ * Example: Pattern A+ B
+ * Row 1: Ctx1 at A (count=1)
+ * Row 2: Ctx1 at A (count=2), Ctx2 at A (count=1)
+ * -> Both at same elemIdx (A), Ctx1.count >= Ctx2.count
+ * -> Ctx2 absorbed
+ *
+ * The asymmetric design (Ctx1 needs hasAbsorbable, Ctx2 needs allAbsorbable)
+ * allows absorption even when Ctx1 has extra non-absorbable states.
+ */
+
+/*
+ * nfa_state_alloc
+ *
+ * Allocate an NFA state, reusing from freeList if available.
+ * freeList is stored in WindowAggState for reuse across match attempts.
+ * Uses flexible array member for counts[].
+ */
+static RPRNFAState *
+nfa_state_alloc(WindowAggState *winstate)
+{
+ RPRNFAState *state;
+
+ /* Try to reuse from free list first */
+ if (winstate->nfaStateFree != NULL)
+ {
+ state = winstate->nfaStateFree;
+ winstate->nfaStateFree = state->next;
+ }
+ else
+ {
+ /* Allocate in partition context for proper lifetime */
+ state = MemoryContextAlloc(winstate->partcontext, winstate->nfaStateSize);
+ }
+
+ /* Initialize entire state to zero */
+ memset(state, 0, winstate->nfaStateSize);
+
+ /* Update statistics */
+ winstate->nfaStatesActive++;
+ winstate->nfaStatesTotalCreated++;
+ if (winstate->nfaStatesActive > winstate->nfaStatesMax)
+ winstate->nfaStatesMax = winstate->nfaStatesActive;
+
+ return state;
+}
+
+/*
+ * nfa_state_free
+ *
+ * Return a state to the free list for later reuse.
+ */
+static void
+nfa_state_free(WindowAggState *winstate, RPRNFAState *state)
+{
+ winstate->nfaStatesActive--;
+ state->next = winstate->nfaStateFree;
+ winstate->nfaStateFree = state;
+}
+
+/*
+ * nfa_state_free_list
+ *
+ * Return all states in a list to the free list.
+ */
+static void
+nfa_state_free_list(WindowAggState *winstate, RPRNFAState *list)
+{
+ RPRNFAState *next;
+
+ for (; list != NULL; list = next)
+ {
+ next = list->next;
+ nfa_state_free(winstate, list);
+ }
+}
+
+/*
+ * nfa_state_create
+ *
+ * Create a new state with given elemIdx and counts.
+ * isAbsorbable is computed immediately: inherited AND new element's flag.
+ * Monotonic property: once false, stays false through all transitions.
+ *
+ * Caller is responsible for linking the returned state.
+ */
+static RPRNFAState *
+nfa_state_create(WindowAggState *winstate, int16 elemIdx,
+ int32 *counts, bool sourceAbsorbable)
+{
+ RPRPattern *pattern = winstate->rpPattern;
+ int maxDepth = pattern->maxDepth;
+ RPRNFAState *state = nfa_state_alloc(winstate);
+ RPRPatternElement *elem = &pattern->elements[elemIdx];
+
+ state->elemIdx = elemIdx;
+ if (counts != NULL && maxDepth > 0)
+ memcpy(state->counts, counts, sizeof(int32) * maxDepth);
+
+ /*
+ * Compute isAbsorbable immediately at transition time. isAbsorbable =
+ * sourceAbsorbable && (elem->flags & ABSORBABLE_BRANCH) Monotonic: once
+ * false, stays false (can't re-enter absorbable region).
+ */
+ state->isAbsorbable = sourceAbsorbable && RPRElemIsAbsorbableBranch(elem);
+
+ return state;
+}
+
+/*
+ * nfa_states_equal
+ *
+ * Check if two states are equivalent (same elemIdx and counts).
+ */
+static bool
+nfa_states_equal(WindowAggState *winstate, RPRNFAState *s1, RPRNFAState *s2)
+{
+ RPRPattern *pattern = winstate->rpPattern;
+ RPRPatternElement *elem;
+ int compareDepth;
+
+ if (s1->elemIdx != s2->elemIdx)
+ return false;
+
+ /* Compare counts up to current element's depth */
+ elem = &pattern->elements[s1->elemIdx];
+ compareDepth = elem->depth + 1; /* depth 0 needs 1 count, etc. */
+
+ if (memcmp(s1->counts, s2->counts, sizeof(int32) * compareDepth) != 0)
+ return false;
+
+ return true;
+}
+
+/*
+ * nfa_add_state_unique
+ *
+ * Add a state to ctx->states at the END, only if no duplicate exists.
+ * Returns true if state was added, false if duplicate found (state is freed).
+ * Earlier states have better lexical order (DFS traversal order), so existing wins.
+ */
+static bool
+nfa_add_state_unique(WindowAggState *winstate, RPRNFAContext *ctx, RPRNFAState *state)
+{
+ RPRNFAState *s;
+ RPRNFAState *tail = NULL;
+
+ /* Check for duplicate and find tail */
+ for (s = ctx->states; s != NULL; s = s->next)
+ {
+ if (nfa_states_equal(winstate, s, state))
+ {
+ /*
+ * Duplicate found - existing has better lexical order, discard
+ * new
+ */
+ nfa_state_free(winstate, state);
+ winstate->nfaStatesMerged++;
+ return false;
+ }
+ tail = s;
+ }
+
+ /* No duplicate, add at end */
+ state->next = NULL;
+ if (tail == NULL)
+ ctx->states = state;
+ else
+ tail->next = state;
+
+ return true;
+}
+
+/*
+ * nfa_add_matched_state
+ *
+ * Record a state that reached FIN, replacing any previous match.
+ *
+ * For SKIP PAST LAST ROW, also prune subsequent contexts whose start row
+ * falls within the match range, as they cannot produce output rows.
+ */
+static void
+nfa_add_matched_state(WindowAggState *winstate, RPRNFAContext *ctx,
+ RPRNFAState *state, int64 matchEndRow)
+{
+ if (ctx->matchedState != NULL)
+ nfa_state_free(winstate, ctx->matchedState);
+
+ ctx->matchedState = state;
+ state->next = NULL;
+ ctx->matchEndRow = matchEndRow;
+
+ /* Prune contexts that started within this match's range */
+ if (winstate->rpSkipTo == ST_PAST_LAST_ROW)
+ {
+ RPRNFAContext *nextCtx;
+ int64 skippedLen;
+
+ while (ctx->next != NULL &&
+ ctx->next->matchStartRow <= matchEndRow)
+ {
+ nextCtx = ctx->next;
+ ctx->next = ctx->next->next;
+
+ Assert(nextCtx->lastProcessedRow >= nextCtx->matchStartRow);
+ skippedLen = nextCtx->lastProcessedRow - nextCtx->matchStartRow + 1;
+ nfa_record_context_skipped(winstate, skippedLen);
+
+ ExecRPRFreeContext(winstate, nextCtx);
+ }
+ if (ctx->next == NULL)
+ winstate->nfaContextTail = ctx;
+ }
+}
+
+/*
+ * nfa_context_alloc
+ *
+ * Allocate an NFA context, reusing from free list if available.
+ */
+static RPRNFAContext *
+nfa_context_alloc(WindowAggState *winstate)
+{
+ RPRNFAContext *ctx;
+
+ if (winstate->nfaContextFree != NULL)
+ {
+ ctx = winstate->nfaContextFree;
+ winstate->nfaContextFree = ctx->next;
+ }
+ else
+ {
+ /* Allocate in partition context for proper lifetime */
+ ctx = MemoryContextAlloc(winstate->partcontext, sizeof(RPRNFAContext));
+ }
+
+ ctx->next = NULL;
+ ctx->prev = NULL;
+ ctx->states = NULL;
+ ctx->matchStartRow = -1;
+ ctx->matchEndRow = -1;
+ ctx->lastProcessedRow = -1;
+ ctx->matchedState = NULL;
+
+ /* Initialize two-flag absorption design based on pattern */
+ ctx->hasAbsorbableState = winstate->rpPattern->isAbsorbable;
+ ctx->allStatesAbsorbable = winstate->rpPattern->isAbsorbable;
+
+ /* Update statistics */
+ winstate->nfaContextsActive++;
+ winstate->nfaContextsTotalCreated++;
+ if (winstate->nfaContextsActive > winstate->nfaContextsMax)
+ winstate->nfaContextsMax = winstate->nfaContextsActive;
+
+ return ctx;
+}
+
+/*
+ * nfa_unlink_context
+ *
+ * Remove a context from the doubly-linked active context list.
+ * Updates head (nfaContext) and tail (nfaContextTail) as needed.
+ */
+static void
+nfa_unlink_context(WindowAggState *winstate, RPRNFAContext *ctx)
+{
+ if (ctx->prev != NULL)
+ ctx->prev->next = ctx->next;
+ else
+ winstate->nfaContext = ctx->next; /* was head */
+
+ if (ctx->next != NULL)
+ ctx->next->prev = ctx->prev;
+ else
+ winstate->nfaContextTail = ctx->prev; /* was tail */
+
+ ctx->next = NULL;
+ ctx->prev = NULL;
+}
+
+/*
+ * nfa_update_length_stats
+ *
+ * Helper function to update min/max/total length statistics.
+ * Called when tracking match/mismatch/absorbed/skipped lengths.
+ */
+static void
+nfa_update_length_stats(int64 count, NFALengthStats *stats, int64 newLen)
+{
+ if (count == 1)
+ {
+ stats->min = newLen;
+ stats->max = newLen;
+ }
+ else
+ {
+ if (newLen < stats->min)
+ stats->min = newLen;
+ if (newLen > stats->max)
+ stats->max = newLen;
+ }
+ stats->total += newLen;
+}
+
+/*
+ * nfa_record_context_skipped
+ *
+ * Record a skipped context in statistics.
+ */
+static void
+nfa_record_context_skipped(WindowAggState *winstate, int64 skippedLen)
+{
+ winstate->nfaContextsSkipped++;
+ nfa_update_length_stats(winstate->nfaContextsSkipped,
+ &winstate->nfaSkippedLen,
+ skippedLen);
+}
+
+/*
+ * nfa_record_context_absorbed
+ *
+ * Record an absorbed context in statistics.
+ */
+static void
+nfa_record_context_absorbed(WindowAggState *winstate, int64 absorbedLen)
+{
+ winstate->nfaContextsAbsorbed++;
+ nfa_update_length_stats(winstate->nfaContextsAbsorbed,
+ &winstate->nfaAbsorbedLen,
+ absorbedLen);
+}
+
+/*
+ * nfa_update_absorption_flags
+ *
+ * Update context's absorption flags after state changes.
+ *
+ * Two flags control absorption behavior:
+ * hasAbsorbableState: true if context has at least one absorbable state.
+ * This flag is monotonic (true -> false only). Once all absorbable states
+ * die, no new absorbable states can be created through transitions.
+ * allStatesAbsorbable: true if ALL states in context are absorbable.
+ * This flag is dynamic and can change false -> true when non-absorbable
+ * states die off.
+ *
+ * Optimization: Once hasAbsorbableState becomes false, both flags remain false
+ * permanently, so we skip recalculation.
+ */
+static void
+nfa_update_absorption_flags(RPRNFAContext *ctx)
+{
+ RPRNFAState *state;
+ bool hasAbsorbable = false;
+ bool allAbsorbable = true;
+
+ /*
+ * Optimization: Once hasAbsorbableState becomes false, it stays false. No
+ * need to recalculate - both flags remain false permanently.
+ */
+ if (!ctx->hasAbsorbableState)
+ {
+ ctx->allStatesAbsorbable = false;
+ return;
+ }
+
+ /* No states means no absorbable states */
+ if (ctx->states == NULL)
+ {
+ ctx->hasAbsorbableState = false;
+ ctx->allStatesAbsorbable = false;
+ return;
+ }
+
+ /*
+ * Iterate through all states to check absorption status. Uses
+ * state->isAbsorbable which tracks if state is in absorbable region. This
+ * is different from RPRElemIsAbsorbable(elem) which checks judgment
+ * point.
+ */
+ for (state = ctx->states; state != NULL; state = state->next)
+ {
+ if (state->isAbsorbable)
+ hasAbsorbable = true;
+ else
+ allAbsorbable = false;
+ }
+
+ ctx->hasAbsorbableState = hasAbsorbable;
+ ctx->allStatesAbsorbable = allAbsorbable;
+}
+
+/*
+ * nfa_states_covered
+ *
+ * Check if all states in newer context are "covered" by older context.
+ *
+ * A newer state is covered when older context has an absorbable state at the
+ * same pattern element (elemIdx) with count >= newer's count at that depth.
+ * The covering state must be absorbable because only absorbable states can
+ * guarantee to produce superset matches.
+ *
+ * If all newer states are covered, newer context's eventual matches will be
+ * a subset of older context's matches, making newer redundant.
+ */
+static bool
+nfa_states_covered(RPRPattern *pattern, RPRNFAContext *older, RPRNFAContext *newer)
+{
+ RPRNFAState *newerState;
+
+ for (newerState = newer->states; newerState != NULL; newerState = newerState->next)
+ {
+ RPRNFAState *olderState;
+ RPRPatternElement *elem;
+ int depth;
+ bool found = false;
+
+ /* All states are absorbable (caller checks allStatesAbsorbable) */
+ elem = &pattern->elements[newerState->elemIdx];
+ depth = elem->depth;
+
+ for (olderState = older->states; olderState != NULL; olderState = olderState->next)
+ {
+ /* Covering state must also be absorbable */
+ if (olderState->isAbsorbable &&
+ olderState->elemIdx == newerState->elemIdx &&
+ olderState->counts[depth] >= newerState->counts[depth])
+ {
+ found = true;
+ break;
+ }
+ }
+
+ if (!found)
+ return false;
+ }
+
+ return true;
+}
+
+/*
+ * nfa_try_absorb_context
+ *
+ * Try to absorb ctx (newer) into an older in-progress context.
+ * Returns true if ctx was absorbed and freed.
+ *
+ * Absorption requires three conditions:
+ * 1. ctx must have all states absorbable (allStatesAbsorbable).
+ * If ctx has any non-absorbable state, it may produce unique matches.
+ * 2. older must have at least one absorbable state (hasAbsorbableState).
+ * Without absorbable states, older cannot cover newer's states.
+ * 3. All ctx states must be covered by older's absorbable states.
+ * This ensures older will produce all matches that ctx would produce.
+ *
+ * Context list is ordered by creation time (oldest first via prev chain).
+ * Each row creates at most one context, so earlier contexts have smaller
+ * matchStartRow values.
+ */
+static void
+nfa_try_absorb_context(WindowAggState *winstate, RPRNFAContext *ctx)
+{
+ RPRPattern *pattern = winstate->rpPattern;
+ RPRNFAContext *older;
+
+ /* Early exit: ctx must have all states absorbable */
+ if (!ctx->allStatesAbsorbable)
+ return;
+
+ for (older = ctx->prev; older != NULL; older = older->prev)
+ {
+ /*
+ * By invariant: ctx->prev chain is in creation order (oldest first),
+ * and each row creates at most one context. So all contexts in this
+ * chain have matchStartRow < ctx->matchStartRow.
+ */
+
+ /* Older must also be in-progress */
+ if (older->states == NULL)
+ continue;
+
+ /* Older must have at least one absorbable state */
+ if (!older->hasAbsorbableState)
+ continue;
+
+ /* Check if all newer states are covered by older */
+ if (nfa_states_covered(pattern, older, ctx))
+ {
+ int64 absorbedLen = ctx->lastProcessedRow - ctx->matchStartRow + 1;
+
+ ExecRPRFreeContext(winstate, ctx);
+ nfa_record_context_absorbed(winstate, absorbedLen);
+ return;
+ }
+ }
+}
+
+/*
+ * nfa_absorb_contexts
+ *
+ * Absorb redundant contexts to reduce memory usage and computation.
+ *
+ * For patterns like A+, newer contexts starting later will produce subset
+ * matches of older contexts with higher counts. By absorbing these redundant
+ * contexts early, we avoid duplicate work.
+ *
+ * Iterates from tail (newest) toward head (oldest) via prev chain.
+ * Only in-progress contexts (states != NULL) are candidates for absorption;
+ * completed contexts represent valid match results.
+ */
+static void
+nfa_absorb_contexts(WindowAggState *winstate)
+{
+ RPRNFAContext *ctx;
+ RPRNFAContext *nextCtx;
+
+ for (ctx = winstate->nfaContextTail; ctx != NULL; ctx = nextCtx)
+ {
+ nextCtx = ctx->prev;
+
+ /*
+ * Only absorb in-progress contexts; completed contexts are valid
+ * results
+ */
+ if (ctx->states != NULL)
+ nfa_try_absorb_context(winstate, ctx);
+ }
+}
+
+/*
+ * nfa_eval_var_match
+ *
+ * Evaluate if a VAR element matches the current row.
+ * Undefined variables (varId >= defineVariableList length) default to TRUE.
+ */
+static bool
+nfa_eval_var_match(WindowAggState *winstate, RPRPatternElement *elem,
+ bool *varMatched)
+{
+ /* This function should only be called for VAR elements */
+ Assert(RPRElemIsVar(elem));
+
+ if (varMatched == NULL)
+ return false;
+ if (elem->varId >= list_length(winstate->defineVariableList))
+ return true;
+ return varMatched[elem->varId];
+}
+
+/*
+ * nfa_match
+ *
+ * Match phase (convergence): evaluate VAR elements against current row.
+ * Only updates counts and removes dead states. Minimal transitions.
+ *
+ * For VAR elements:
+ * - matched: count++, keep state (unless count > max)
+ * - not matched: remove state (exit alternatives already exist from
+ * previous advance when count >= min was satisfied)
+ *
+ * For simple VARs (min=max=1) followed by END:
+ * - Advance to END and update group count before absorb phase
+ * - This ensures absorption can compare states by group completion
+ *
+ * Non-VAR elements (ALT, END, FIN) are kept as-is for advance phase.
+ */
+static void
+nfa_match(WindowAggState *winstate, RPRNFAContext *ctx, bool *varMatched)
+{
+ RPRPattern *pattern = winstate->rpPattern;
+ RPRPatternElement *elements = pattern->elements;
+ RPRNFAState **prevPtr = &ctx->states;
+ RPRNFAState *state;
+ RPRNFAState *nextState;
+
+ /*
+ * Evaluate VAR elements against current row. For simple VARs with END
+ * next, advance to END and update group count inline so absorb phase can
+ * compare states properly.
+ */
+ for (state = ctx->states; state != NULL; state = nextState)
+ {
+ RPRPatternElement *elem = &elements[state->elemIdx];
+
+ nextState = state->next;
+
+ if (RPRElemIsVar(elem))
+ {
+ bool matched;
+ int depth = elem->depth;
+ int32 count = state->counts[depth];
+
+ matched = nfa_eval_var_match(winstate, elem, varMatched);
+
+ if (matched)
+ {
+ /* Increment count */
+ if (count < RPR_COUNT_MAX)
+ count++;
+
+ /* Max constraint should not be exceeded */
+ Assert(elem->max == RPR_QUANTITY_INF || count <= elem->max);
+
+ state->counts[depth] = count;
+
+ /*
+ * For simple VAR (min=max=1) with END next, advance to END
+ * and update group count inline. This keeps state in place,
+ * preserving lexical order.
+ */
+ if (elem->min == 1 && elem->max == 1 &&
+ RPRElemIsEnd(&elements[elem->next]))
+ {
+ RPRPatternElement *endElem = &elements[elem->next];
+ int endDepth = endElem->depth;
+ int32 endCount = state->counts[endDepth];
+
+ Assert(count == 1);
+
+ /* Increment group count with overflow protection */
+ if (endCount < RPR_COUNT_MAX)
+ endCount++;
+
+ /*
+ * END's max can never be exceeded here because
+ * nfa_advance_end only loops when count < max, so
+ * endCount entering inline advance is at most max-1, and
+ * incrementing yields at most max.
+ */
+ Assert(endElem->max == RPR_QUANTITY_INF ||
+ endCount <= endElem->max);
+
+ state->elemIdx = elem->next;
+ state->counts[endDepth] = endCount;
+ }
+ /* else: stay at VAR for advance phase */
+ }
+ else
+ {
+ /*
+ * Not matched - remove state. Exit alternatives were already
+ * created by advance phase when count >= min was satisfied.
+ */
+ *prevPtr = nextState;
+ nfa_state_free(winstate, state);
+ continue;
+ }
+ }
+ /* Non-VAR elements: keep as-is for advance phase */
+
+ prevPtr = &state->next;
+ }
+}
+
+/*
+ * nfa_route_to_elem
+ *
+ * Route state to next element. If VAR, add to ctx->states and process
+ * skip path if optional. Otherwise, continue epsilon expansion via recursion.
+ */
+static void
+nfa_route_to_elem(WindowAggState *winstate, RPRNFAContext *ctx,
+ RPRNFAState *state, RPRPatternElement *nextElem,
+ int64 currentPos)
+{
+ if (RPRElemIsVar(nextElem))
+ {
+ RPRNFAState *skipState = NULL;
+
+ /* Create skip state before add_unique, which may free state */
+ if (RPRElemCanSkip(nextElem))
+ skipState = nfa_state_create(winstate, nextElem->next,
+ state->counts, state->isAbsorbable);
+
+ nfa_add_state_unique(winstate, ctx, state);
+
+ if (skipState != NULL)
+ nfa_advance_state(winstate, ctx, skipState, currentPos);
+ }
+ else
+ {
+ nfa_advance_state(winstate, ctx, state, currentPos);
+ }
+}
+
+/*
+ * nfa_advance_alt
+ *
+ * Handle ALT element: expand all branches in lexical order via DFS.
+ */
+static void
+nfa_advance_alt(WindowAggState *winstate, RPRNFAContext *ctx,
+ RPRNFAState *state, RPRPatternElement *elem,
+ int64 currentPos)
+{
+ RPRPattern *pattern = winstate->rpPattern;
+ RPRPatternElement *elements = pattern->elements;
+ RPRElemIdx altIdx = elem->next;
+
+ while (altIdx >= 0 && altIdx < pattern->numElements)
+ {
+ RPRPatternElement *altElem = &elements[altIdx];
+ RPRNFAState *newState;
+
+ /* Stop if element is outside ALT scope (not a branch) */
+ if (altElem->depth <= elem->depth)
+ break;
+
+ /* Create independent state for each branch */
+ newState = nfa_state_create(winstate, altIdx,
+ state->counts, state->isAbsorbable);
+
+ /* Recursively process this branch before next */
+ nfa_advance_state(winstate, ctx, newState, currentPos);
+ altIdx = altElem->jump;
+ }
+
+ nfa_state_free(winstate, state);
+}
+
+/*
+ * nfa_advance_begin
+ *
+ * Handle BEGIN element: group entry logic.
+ * BEGIN is only visited at initial group entry (count is always 0).
+ * If min=0, creates a skip path past the group.
+ * Loop-back from END goes directly to first child, bypassing BEGIN.
+ */
+static void
+nfa_advance_begin(WindowAggState *winstate, RPRNFAContext *ctx,
+ RPRNFAState *state, RPRPatternElement *elem,
+ int64 currentPos)
+{
+ RPRPattern *pattern = winstate->rpPattern;
+ RPRPatternElement *elements = pattern->elements;
+ RPRNFAState *skipState = NULL;
+
+ state->counts[elem->depth] = 0;
+
+ /* Optional group: create skip path (but don't route yet) */
+ if (elem->min == 0)
+ {
+ skipState = nfa_state_create(winstate, elem->jump,
+ state->counts, state->isAbsorbable);
+ }
+
+ if (skipState != NULL && RPRElemIsReluctant(elem))
+ {
+ RPRNFAState *savedMatch = ctx->matchedState;
+
+ /* Reluctant: skip first (prefer fewer iterations), enter second */
+ nfa_route_to_elem(winstate, ctx, skipState,
+ &elements[elem->jump], currentPos);
+
+ /*
+ * If skip path reached FIN, shortest match is found. Skip group entry
+ * to prevent longer matches.
+ */
+ if (ctx->matchedState != savedMatch)
+ {
+ nfa_state_free(winstate, state);
+ return;
+ }
+
+ state->elemIdx = elem->next;
+ nfa_route_to_elem(winstate, ctx, state,
+ &elements[state->elemIdx], currentPos);
+ }
+ else
+ {
+ /* Greedy: enter first, skip second */
+ state->elemIdx = elem->next;
+ nfa_route_to_elem(winstate, ctx, state,
+ &elements[state->elemIdx], currentPos);
+
+ if (skipState != NULL)
+ {
+ nfa_route_to_elem(winstate, ctx, skipState,
+ &elements[elem->jump], currentPos);
+ }
+ }
+}
+
+/*
+ * nfa_advance_end
+ *
+ * Handle END element: group repetition logic.
+ * Decides whether to loop back or exit based on count vs min/max.
+ */
+static void
+nfa_advance_end(WindowAggState *winstate, RPRNFAContext *ctx,
+ RPRNFAState *state, RPRPatternElement *elem,
+ int64 currentPos)
+{
+ RPRPattern *pattern = winstate->rpPattern;
+ RPRPatternElement *elements = pattern->elements;
+ int depth = elem->depth;
+ int32 count = state->counts[depth];
+
+ if (count < elem->min)
+ {
+ RPRPatternElement *jumpElem;
+ RPRNFAState *ffState = NULL;
+
+ /* Snapshot state for ff path before modifying for loop-back */
+ if (RPRElemCanEmptyLoop(elem))
+ ffState = nfa_state_create(winstate, state->elemIdx,
+ state->counts, state->isAbsorbable);
+
+ /* Loop back for real matches (primary path) */
+ for (int d = depth + 1; d < pattern->maxDepth; d++)
+ state->counts[d] = 0;
+ state->elemIdx = elem->jump;
+ jumpElem = &elements[state->elemIdx];
+ nfa_route_to_elem(winstate, ctx, state, jumpElem,
+ currentPos);
+
+ /*
+ * Fast-forward fallback for nullable bodies. E.g. (A?){2,3} when A
+ * doesn't match: the loop-back produces empty iterations that cycle
+ * detection would kill. Instead, exit directly treating all
+ * remaining required iterations as empty. Route to elem->next (not
+ * nfa_advance_end) to avoid creating competing greedy/reluctant loop
+ * states.
+ */
+ if (ffState != NULL)
+ {
+ RPRPatternElement *nextElem;
+
+ ffState->counts[depth] = 0;
+ ffState->elemIdx = elem->next;
+ nextElem = &elements[ffState->elemIdx];
+
+ /* END->END: increment outer END's count */
+ if (RPRElemIsEnd(nextElem) &&
+ ffState->counts[nextElem->depth] < RPR_COUNT_MAX)
+ ffState->counts[nextElem->depth]++;
+
+ nfa_route_to_elem(winstate, ctx, ffState, nextElem,
+ currentPos);
+ }
+ }
+ else if (elem->max != RPR_QUANTITY_INF && count >= elem->max)
+ {
+ /* Must exit: reached max iterations. */
+ RPRPatternElement *nextElem;
+
+ state->counts[depth] = 0;
+ state->elemIdx = elem->next;
+ nextElem = &elements[state->elemIdx];
+
+ /* END->END: increment outer END's count */
+ if (RPRElemIsEnd(nextElem) && state->counts[nextElem->depth] < RPR_COUNT_MAX)
+ state->counts[nextElem->depth]++;
+
+ nfa_route_to_elem(winstate, ctx, state, nextElem, currentPos);
+ }
+ else
+ {
+ /*
+ * Between min and max (with at least one iteration) - can exit or
+ * loop. Greedy: loop first (prefer more iterations). Reluctant: exit
+ * first (prefer fewer iterations).
+ */
+ RPRNFAState *exitState;
+ RPRPatternElement *jumpElem;
+ RPRPatternElement *nextElem;
+
+ /*
+ * Create exit state first (need original counts before modifying
+ * state)
+ */
+ exitState = nfa_state_create(winstate, elem->next,
+ state->counts, state->isAbsorbable);
+ exitState->counts[depth] = 0;
+ nextElem = &elements[exitState->elemIdx];
+
+ /* END->END: increment outer END's count */
+ if (RPRElemIsEnd(nextElem) && exitState->counts[nextElem->depth] < RPR_COUNT_MAX)
+ exitState->counts[nextElem->depth]++;
+
+ /* Prepare loop state */
+ for (int d = depth + 1; d < pattern->maxDepth; d++)
+ state->counts[d] = 0;
+ state->elemIdx = elem->jump;
+ jumpElem = &elements[state->elemIdx];
+
+ if (RPRElemIsReluctant(elem))
+ {
+ RPRNFAState *savedMatch = ctx->matchedState;
+
+ /* Exit first (preferred for reluctant) */
+ nfa_route_to_elem(winstate, ctx, exitState, nextElem,
+ currentPos);
+
+ /*
+ * If exit path reached FIN, shortest match is found. Skip loop to
+ * prevent longer matches from replacing it.
+ */
+ if (ctx->matchedState != savedMatch)
+ {
+ nfa_state_free(winstate, state);
+ return;
+ }
+
+ /* Loop second */
+ nfa_route_to_elem(winstate, ctx, state, jumpElem,
+ currentPos);
+ }
+ else
+ {
+ /* Loop first (preferred for greedy) */
+ nfa_route_to_elem(winstate, ctx, state, jumpElem,
+ currentPos);
+ /* Exit second */
+ nfa_route_to_elem(winstate, ctx, exitState, nextElem,
+ currentPos);
+ }
+ }
+}
+
+/*
+ * nfa_advance_var
+ *
+ * Handle VAR element: loop/exit transitions.
+ * After match phase, all VAR states have matched - decide next action.
+ */
+static void
+nfa_advance_var(WindowAggState *winstate, RPRNFAContext *ctx,
+ RPRNFAState *state, RPRPatternElement *elem,
+ int64 currentPos)
+{
+ RPRPattern *pattern = winstate->rpPattern;
+ RPRPatternElement *elements = pattern->elements;
+ int depth = elem->depth;
+ int32 count = state->counts[depth];
+ bool canLoop = (elem->max == RPR_QUANTITY_INF || count < elem->max);
+ bool canExit = (count >= elem->min);
+
+ /* After a successful match, count >= 1, so at least one must be true */
+ Assert(canLoop || canExit);
+
+ if (canLoop && canExit)
+ {
+ /*
+ * Both loop and exit possible. Greedy: loop first (prefer longer
+ * match). Reluctant: exit first (prefer shorter match).
+ */
+ RPRNFAState *cloneState;
+ RPRPatternElement *nextElem;
+ bool reluctant = RPRElemIsReluctant(elem);
+
+ /*
+ * Clone state for the second-priority path. For greedy, clone is the
+ * loop state; for reluctant, clone is the exit state.
+ */
+ if (reluctant)
+ {
+ RPRNFAState *savedMatch = ctx->matchedState;
+
+ /* Clone for exit, original stays for loop */
+ cloneState = nfa_state_create(winstate, elem->next,
+ state->counts, state->isAbsorbable);
+ cloneState->counts[depth] = 0;
+ nextElem = &elements[cloneState->elemIdx];
+
+ /* When exiting directly to an outer END, increment its count */
+ if (RPRElemIsEnd(nextElem))
+ {
+ if (cloneState->counts[nextElem->depth] < RPR_COUNT_MAX)
+ cloneState->counts[nextElem->depth]++;
+ }
+
+ /* Exit first (preferred for reluctant) */
+ nfa_route_to_elem(winstate, ctx, cloneState, nextElem,
+ currentPos);
+
+ /*
+ * If exit path reached FIN, the shortest match is found. Skip
+ * loop state to prevent longer matches from replacing it.
+ */
+ if (ctx->matchedState != savedMatch)
+ {
+ nfa_state_free(winstate, state);
+ return;
+ }
+
+ /* Loop second */
+ nfa_add_state_unique(winstate, ctx, state);
+ }
+ else
+ {
+ /* Clone for loop, original used for exit */
+ cloneState = nfa_state_create(winstate, state->elemIdx,
+ state->counts, state->isAbsorbable);
+
+ /* Loop first (preferred for greedy) */
+ nfa_add_state_unique(winstate, ctx, cloneState);
+
+ /* Exit second */
+ state->counts[depth] = 0;
+ state->elemIdx = elem->next;
+ nextElem = &elements[state->elemIdx];
+
+ /*
+ * When exiting directly to an outer END, increment its iteration
+ * count. Simple VARs (min=max=1) handle this via inline advance
+ * in nfa_match, but quantified VARs bypass that path.
+ */
+ if (RPRElemIsEnd(nextElem))
+ {
+ if (state->counts[nextElem->depth] < RPR_COUNT_MAX)
+ state->counts[nextElem->depth]++;
+ }
+
+ nfa_route_to_elem(winstate, ctx, state, nextElem,
+ currentPos);
+ }
+ }
+ else if (canLoop)
+ {
+ /* Loop only: keep state as-is */
+ nfa_add_state_unique(winstate, ctx, state);
+ }
+ else if (canExit)
+ {
+ /* Exit only: advance to next element */
+ RPRPatternElement *nextElem;
+
+ state->counts[depth] = 0;
+ state->elemIdx = elem->next;
+ nextElem = &elements[state->elemIdx];
+
+ /* See comment above: increment outer END count for quantified VARs */
+ if (RPRElemIsEnd(nextElem))
+ {
+ if (state->counts[nextElem->depth] < RPR_COUNT_MAX)
+ state->counts[nextElem->depth]++;
+ }
+
+ nfa_route_to_elem(winstate, ctx, state, nextElem, currentPos);
+ }
+}
+
+/*
+ * nfa_advance_state
+ *
+ * Recursively process a single state through epsilon transitions.
+ * DFS traversal ensures states are added to ctx->states in lexical order.
+ */
+static void
+nfa_advance_state(WindowAggState *winstate, RPRNFAContext *ctx,
+ RPRNFAState *state, int64 currentPos)
+{
+ RPRPattern *pattern = winstate->rpPattern;
+ RPRPatternElement *elem;
+
+ Assert(state->elemIdx >= 0 && state->elemIdx < pattern->numElements);
+
+ /* Cycle detection: if this elemIdx was already visited in this DFS, bail */
+ if (winstate->nfaVisitedElems[WORDNUM(state->elemIdx)] &
+ ((bitmapword) 1 << BITNUM(state->elemIdx)))
+ {
+ nfa_state_free(winstate, state);
+ return;
+ }
+ winstate->nfaVisitedElems[WORDNUM(state->elemIdx)] |=
+ ((bitmapword) 1 << BITNUM(state->elemIdx));
+
+ elem = &pattern->elements[state->elemIdx];
+
+ switch (elem->varId)
+ {
+ case RPR_VARID_FIN:
+ /* FIN: record match */
+ nfa_add_matched_state(winstate, ctx, state, currentPos);
+ break;
+
+ case RPR_VARID_ALT:
+ nfa_advance_alt(winstate, ctx, state, elem, currentPos);
+ break;
+
+ case RPR_VARID_BEGIN:
+ nfa_advance_begin(winstate, ctx, state, elem, currentPos);
+ break;
+
+ case RPR_VARID_END:
+ nfa_advance_end(winstate, ctx, state, elem, currentPos);
+ break;
+
+ default:
+ /* VAR element */
+ nfa_advance_var(winstate, ctx, state, elem, currentPos);
+ break;
+ }
+}
+
+/*
+ * nfa_advance
+ *
+ * Advance phase (divergence): transition from all surviving states.
+ * Called after match phase with matched VAR states, or at context creation
+ * for initial epsilon expansion (with currentPos = startPos - 1).
+ *
+ * Processes states in order, using recursive DFS to maintain lexical order.
+ */
+static void
+nfa_advance(WindowAggState *winstate, RPRNFAContext *ctx, int64 currentPos)
+{
+ RPRNFAState *states = ctx->states;
+ RPRNFAState *state;
+
+ ctx->states = NULL; /* Will rebuild */
+
+ /* Process each state in lexical order (DFS order from previous advance) */
+ while (states != NULL)
+ {
+ RPRNFAState *savedMatchedState = ctx->matchedState;
+
+ /* Clear visited bitmap before each state's DFS expansion */
+ memset(winstate->nfaVisitedElems, 0,
+ sizeof(bitmapword) * winstate->nfaVisitedNWords);
+
+ state = states;
+ states = states->next;
+ state->next = NULL;
+
+ nfa_advance_state(winstate, ctx, state, currentPos);
+
+ /*
+ * Early termination: if a FIN was newly reached in this advance,
+ * remaining old states have worse lexical order and can be pruned.
+ * Only check for new FIN arrivals (not ones from previous rows).
+ */
+ if (ctx->matchedState != savedMatchedState && states != NULL)
+ {
+ nfa_state_free_list(winstate, states);
+ break;
+ }
+ }
+}
+
+
+/***********************************************************************
+ * API exposed to nodeWindowAgg.c
+ ***********************************************************************/
+
+/*
+ * ExecRPRStartContext
+ *
+ * Start a new match context at given position.
+ * Initializes context, state absorption flags, and performs initial advance
+ * to expand epsilon transitions (ALT branches, optional elements).
+ * Adds context to the tail of winstate->nfaContext list.
+ */
+RPRNFAContext *
+ExecRPRStartContext(WindowAggState *winstate, int64 startPos)
+{
+ RPRNFAContext *ctx;
+ RPRPattern *pattern = winstate->rpPattern;
+ RPRPatternElement *elem;
+
+ ctx = nfa_context_alloc(winstate);
+ ctx->matchStartRow = startPos;
+ ctx->states = nfa_state_alloc(winstate); /* initial state at elem 0 */
+
+ elem = &pattern->elements[0];
+
+ if (RPRElemIsAbsorbableBranch(elem))
+ {
+ ctx->states->isAbsorbable = true;
+ }
+ else
+ {
+ ctx->hasAbsorbableState = false;
+ ctx->allStatesAbsorbable = false;
+ ctx->states->isAbsorbable = false;
+ }
+
+ /* Add to tail of active context list (doubly-linked, oldest-first) */
+ ctx->prev = winstate->nfaContextTail;
+ ctx->next = NULL;
+ if (winstate->nfaContextTail != NULL)
+ winstate->nfaContextTail->next = ctx;
+ else
+ winstate->nfaContext = ctx; /* first context becomes head */
+ winstate->nfaContextTail = ctx;
+
+ /*
+ * Initial advance (divergence): expand ALT branches and create exit
+ * states for VAR elements with min=0. This prepares the context for the
+ * first row's match phase.
+ *
+ * Use startPos - 1 as currentPos since no row has been consumed yet. If
+ * FIN is reached via epsilon transitions, matchEndRow = startPos - 1
+ * which is less than matchStartRow, resulting in UNMATCHED treatment.
+ */
+ nfa_advance(winstate, ctx, startPos - 1);
+
+ return ctx;
+}
+
+/*
+ * ExecRPRGetHeadContext
+ *
+ * Return the head context if its start position matches pos.
+ * Returns NULL if no context exists or head doesn't match pos.
+ */
+RPRNFAContext *
+ExecRPRGetHeadContext(WindowAggState *winstate, int64 pos)
+{
+ RPRNFAContext *ctx = winstate->nfaContext;
+
+ /*
+ * Contexts are sorted by matchStartRow ascending. If the head context
+ * doesn't match pos, no context exists for this position.
+ */
+ if (ctx == NULL || ctx->matchStartRow != pos)
+ return NULL;
+
+ return ctx;
+}
+
+/*
+ * ExecRPRFreeContext
+ *
+ * Unlink context from active list and return it to free list.
+ * Also frees any states in the context.
+ */
+void
+ExecRPRFreeContext(WindowAggState *winstate, RPRNFAContext *ctx)
+{
+ /* Unlink from active list first */
+ nfa_unlink_context(winstate, ctx);
+
+ /* Update statistics */
+ winstate->nfaContextsActive--;
+
+ if (ctx->states != NULL)
+ nfa_state_free_list(winstate, ctx->states);
+ if (ctx->matchedState != NULL)
+ nfa_state_free(winstate, ctx->matchedState);
+
+ ctx->states = NULL;
+ ctx->matchedState = NULL;
+ ctx->next = winstate->nfaContextFree;
+ winstate->nfaContextFree = ctx;
+}
+
+/*
+ * ExecRPRRecordContextSuccess
+ *
+ * Record a successful context in statistics.
+ */
+void
+ExecRPRRecordContextSuccess(WindowAggState *winstate, int64 matchLen)
+{
+ winstate->nfaMatchesSucceeded++;
+ nfa_update_length_stats(winstate->nfaMatchesSucceeded,
+ &winstate->nfaMatchLen,
+ matchLen);
+}
+
+/*
+ * ExecRPRRecordContextFailure
+ *
+ * Record a failed context in statistics.
+ * If failedLen == 1, count as pruned (failed on first row).
+ * If failedLen > 1, count as mismatched and update length stats.
+ */
+void
+ExecRPRRecordContextFailure(WindowAggState *winstate, int64 failedLen)
+{
+ if (failedLen == 1)
+ {
+ winstate->nfaContextsPruned++;
+ }
+ else
+ {
+ winstate->nfaMatchesFailed++;
+ nfa_update_length_stats(winstate->nfaMatchesFailed,
+ &winstate->nfaFailLen,
+ failedLen);
+ }
+}
+
+/*
+ * ExecRPRProcessRow
+ *
+ * Process all contexts for one row:
+ * 1. Match all contexts (convergence) - evaluate VARs, prune dead states
+ * 2. Absorb redundant contexts - ideal timing after convergence
+ * 3. Advance all contexts (divergence) - create new states for next row
+ */
+void
+ExecRPRProcessRow(WindowAggState *winstate, int64 currentPos,
+ bool hasLimitedFrame, int64 frameOffset)
+{
+ RPRNFAContext *ctx;
+ bool *varMatched = winstate->nfaVarMatched;
+
+ /*
+ * Phase 1: Match all contexts (convergence). Evaluate VAR elements,
+ * update counts, remove dead states.
+ */
+ for (ctx = winstate->nfaContext; ctx != NULL; ctx = ctx->next)
+ {
+ if (ctx->states == NULL)
+ continue;
+
+ /* Check frame boundary - finalize if exceeded */
+ if (hasLimitedFrame)
+ {
+ int64 ctxFrameEnd = ctx->matchStartRow + frameOffset + 1;
+
+ if (currentPos >= ctxFrameEnd)
+ {
+ /* Frame boundary exceeded: force mismatch */
+ nfa_match(winstate, ctx, NULL);
+ continue;
+ }
+ }
+
+ nfa_match(winstate, ctx, varMatched);
+ ctx->lastProcessedRow = currentPos;
+ }
+
+ /*
+ * Phase 2: Absorb redundant contexts. After match phase, states have
+ * converged - ideal for absorption. First update absorption flags that
+ * may have changed due to state removal.
+ */
+ if (winstate->rpPattern->isAbsorbable)
+ {
+ for (ctx = winstate->nfaContext; ctx != NULL; ctx = ctx->next)
+ nfa_update_absorption_flags(ctx);
+
+ nfa_absorb_contexts(winstate);
+ }
+
+ /*
+ * Phase 3: Advance all contexts (divergence). Create new states
+ * (loop/exit) from surviving matched states.
+ */
+ for (ctx = winstate->nfaContext; ctx != NULL; ctx = ctx->next)
+ {
+ if (ctx->states == NULL)
+ continue;
+
+ /*
+ * Phase 1 already handled frame boundary exceeded contexts by forcing
+ * mismatch (nfa_match with NULL), which removes all states (all
+ * states are at VAR positions after advance). So any surviving
+ * context here must be within its frame boundary.
+ */
+ Assert(!hasLimitedFrame ||
+ currentPos < ctx->matchStartRow + frameOffset + 1);
+
+ nfa_advance(winstate, ctx, currentPos);
+ }
+}
+
+/*
+ * ExecRPRCleanupDeadContexts
+ *
+ * Remove contexts that have failed (no active states and no match).
+ * These are contexts that failed during normal processing and should be
+ * counted as pruned (if length 1) or mismatched (if length > 1).
+ */
+void
+ExecRPRCleanupDeadContexts(WindowAggState *winstate, RPRNFAContext *excludeCtx)
+{
+ RPRNFAContext *ctx;
+ RPRNFAContext *next;
+
+ for (ctx = winstate->nfaContext; ctx != NULL; ctx = next)
+ {
+ next = ctx->next;
+
+ /* Skip the target context and contexts still processing */
+ if (ctx == excludeCtx || ctx->states != NULL)
+ continue;
+
+ /* Skip successfully matched contexts (will be handled by SKIP logic) */
+ if (ctx->matchEndRow >= ctx->matchStartRow)
+ continue;
+
+ /*
+ * This is a failed context - count and remove it. Only count if it
+ * actually processed its start row. Contexts created for
+ * beyond-partition rows are silently removed.
+ */
+ if (ctx->lastProcessedRow >= ctx->matchStartRow)
+ {
+ int64 failedLen = ctx->lastProcessedRow - ctx->matchStartRow + 1;
+
+ ExecRPRRecordContextFailure(winstate, failedLen);
+ }
+ /* else: context was never processed (beyond-partition), just remove */
+
+ ExecRPRFreeContext(winstate, ctx);
+ }
+}
+
+/*
+ * ExecRPRFinalizeAllContexts
+ *
+ * Finalize all active contexts when partition ends.
+ * Match with NULL to force mismatch, then advance to process epsilon transitions.
+ */
+void
+ExecRPRFinalizeAllContexts(WindowAggState *winstate, int64 lastPos)
+{
+ RPRNFAContext *ctx;
+
+ for (ctx = winstate->nfaContext; ctx != NULL; ctx = ctx->next)
+ {
+ if (ctx->states != NULL)
+ {
+ nfa_match(winstate, ctx, NULL);
+ nfa_advance(winstate, ctx, lastPos);
+ }
+ }
+}
diff --git a/src/backend/executor/meson.build b/src/backend/executor/meson.build
index dc45be0b2ce..0ff4a5b1d83 100644
--- a/src/backend/executor/meson.build
+++ b/src/backend/executor/meson.build
@@ -13,6 +13,7 @@ backend_sources += files(
'execParallel.c',
'execPartition.c',
'execProcnode.c',
+ 'execRPR.c',
'execReplication.c',
'execSRF.c',
'execScan.c',
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 784ceeb8246..8d25c123ecb 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -36,19 +36,25 @@
#include "access/htup_details.h"
#include "catalog/objectaccess.h"
#include "catalog/pg_aggregate.h"
+#include "catalog/pg_collation_d.h"
#include "catalog/pg_proc.h"
#include "executor/executor.h"
+#include "executor/execRPR.h"
#include "executor/instrument.h"
#include "executor/nodeWindowAgg.h"
#include "miscadmin.h"
#include "nodes/nodeFuncs.h"
+#include "nodes/plannodes.h"
#include "optimizer/clauses.h"
#include "optimizer/optimizer.h"
+#include "optimizer/rpr.h"
#include "parser/parse_agg.h"
#include "parser/parse_coerce.h"
+#include "regex/regex.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/datum.h"
+#include "utils/fmgroids.h"
#include "utils/expandeddatum.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
@@ -172,6 +178,15 @@ typedef struct WindowStatePerAggData
bool restart; /* need to restart this agg in this cycle? */
} WindowStatePerAggData;
+/*
+ * Structure used by check_rpr_navigation() and rpr_navigation_walker().
+ */
+typedef struct NavigationInfo
+{
+ bool is_prev; /* true if PREV */
+ int num_vars; /* number of var nodes */
+} NavigationInfo;
+
static void initialize_windowaggregate(WindowAggState *winstate,
WindowStatePerFunc perfuncstate,
WindowStatePerAgg peraggstate);
@@ -208,6 +223,9 @@ static Datum GetAggInitVal(Datum textInitVal, Oid transtype);
static bool are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
TupleTableSlot *slot2);
+static int WinGetSlotInFrame(WindowObject winobj, TupleTableSlot *slot,
+ int relpos, int seektype, bool set_mark,
+ bool *isnull, bool *isout);
static bool window_gettupleslot(WindowObject winobj, int64 pos,
TupleTableSlot *slot);
@@ -226,6 +244,24 @@ static uint8 get_notnull_info(WindowObject winobj,
int64 pos, int argno);
static void put_notnull_info(WindowObject winobj,
int64 pos, int argno, bool isnull);
+static void attno_map(Node *node);
+static bool attno_map_walker(Node *node, void *context);
+
+static bool rpr_is_defined(WindowAggState *winstate);
+static int row_is_in_reduced_frame(WindowObject winobj, int64 pos);
+
+static void create_reduced_frame_map(WindowAggState *winstate);
+static void clear_reduced_frame_map(WindowAggState *winstate);
+static int get_reduced_frame_map(WindowAggState *winstate, int64 pos);
+static void register_reduced_frame_map(WindowAggState *winstate, int64 pos,
+ int val);
+static void update_reduced_frame(WindowObject winobj, int64 pos);
+
+static void check_rpr_navigation(Node *node, bool is_prev);
+static bool rpr_navigation_walker(Node *node, void *context);
+
+/* Forward declarations - NFA row evaluation */
+static bool nfa_evaluate_row(WindowObject winobj, int64 pos, bool *varMatched);
/*
* Not null info bit array consists of 2-bit items
@@ -819,6 +855,7 @@ eval_windowaggregates(WindowAggState *winstate)
* transition function, or
* - we have an EXCLUSION clause, or
* - if the new frame doesn't overlap the old one
+ * - if RPR is enabled
*
* Note that we don't strictly need to restart in the last case, but if
* we're going to remove all rows from the aggregation anyway, a restart
@@ -833,7 +870,8 @@ eval_windowaggregates(WindowAggState *winstate)
(winstate->aggregatedbase != winstate->frameheadpos &&
!OidIsValid(peraggstate->invtransfn_oid)) ||
(winstate->frameOptions & FRAMEOPTION_EXCLUSION) ||
- winstate->aggregatedupto <= winstate->frameheadpos)
+ winstate->aggregatedupto <= winstate->frameheadpos ||
+ rpr_is_defined(winstate))
{
peraggstate->restart = true;
numaggs_restart++;
@@ -907,7 +945,22 @@ eval_windowaggregates(WindowAggState *winstate)
* head, so that tuplestore can discard unnecessary rows.
*/
if (agg_winobj->markptr >= 0)
- WinSetMarkPosition(agg_winobj, winstate->frameheadpos);
+ {
+ int64 markpos = winstate->frameheadpos;
+
+ if (rpr_is_defined(winstate))
+ {
+ /*
+ * If RPR is used, it is possible PREV wants to look at the
+ * previous row. So the mark pos should be frameheadpos - 1
+ * unless it is below 0.
+ */
+ markpos -= 1;
+ if (markpos < 0)
+ markpos = 0;
+ }
+ WinSetMarkPosition(agg_winobj, markpos);
+ }
/*
* Now restart the aggregates that require it.
@@ -962,6 +1015,14 @@ eval_windowaggregates(WindowAggState *winstate)
{
winstate->aggregatedupto = winstate->frameheadpos;
ExecClearTuple(agg_row_slot);
+
+ /*
+ * If RPR is defined, we do not use aggregatedupto_nonrestarted. To
+ * avoid assertion failure below, we reset aggregatedupto_nonrestarted
+ * to frameheadpos.
+ */
+ if (rpr_is_defined(winstate))
+ aggregatedupto_nonrestarted = winstate->frameheadpos;
}
/*
@@ -975,6 +1036,12 @@ eval_windowaggregates(WindowAggState *winstate)
{
int ret;
+#ifdef RPR_DEBUG
+ printf("===== loop in frame starts: aggregatedupto: " INT64_FORMAT " aggregatedbase: " INT64_FORMAT "\n",
+ winstate->aggregatedupto,
+ winstate->aggregatedbase);
+#endif
+
/* Fetch next row if we didn't already */
if (TupIsNull(agg_row_slot))
{
@@ -991,9 +1058,53 @@ eval_windowaggregates(WindowAggState *winstate)
agg_row_slot, false);
if (ret < 0)
break;
+
if (ret == 0)
goto next_tuple;
+ if (rpr_is_defined(winstate))
+ {
+#ifdef RPR_DEBUG
+ printf("reduced_frame_map: %d aggregatedupto: " INT64_FORMAT " aggregatedbase: " INT64_FORMAT "\n",
+ get_reduced_frame_map(winstate,
+ winstate->aggregatedupto),
+ winstate->aggregatedupto,
+ winstate->aggregatedbase);
+#endif
+
+ /*
+ * If the row status at currentpos is already decided and current
+ * row status is not decided yet, it means we passed the last
+ * reduced frame. Time to break the loop.
+ */
+ if (get_reduced_frame_map(winstate, winstate->currentpos)
+ != RF_NOT_DETERMINED &&
+ get_reduced_frame_map(winstate, winstate->aggregatedupto)
+ == RF_NOT_DETERMINED)
+ break;
+
+ /*
+ * Otherwise we need to calculate the reduced frame.
+ */
+ ret = row_is_in_reduced_frame(winstate->agg_winobj,
+ winstate->aggregatedupto);
+ if (ret == -1) /* unmatched row */
+ break;
+
+ /*
+ * Check if current row needs to be skipped due to no match.
+ */
+ if (get_reduced_frame_map(winstate,
+ winstate->aggregatedupto) == RF_SKIPPED &&
+ winstate->aggregatedupto == winstate->aggregatedbase)
+ {
+#ifdef RPR_DEBUG
+ printf("skip current row for aggregation\n");
+#endif
+ break;
+ }
+ }
+
/* Set tuple context for evaluation of aggregate arguments */
winstate->tmpcontext->ecxt_outertuple = agg_row_slot;
@@ -1022,6 +1133,7 @@ next_tuple:
ExecClearTuple(agg_row_slot);
}
+
/* The frame's end is not supposed to move backwards, ever */
Assert(aggregatedupto_nonrestarted <= winstate->aggregatedupto);
@@ -1245,6 +1357,7 @@ begin_partition(WindowAggState *winstate)
winstate->framehead_valid = false;
winstate->frametail_valid = false;
winstate->grouptail_valid = false;
+ create_reduced_frame_map(winstate);
winstate->spooled_rows = 0;
winstate->currentpos = 0;
winstate->frameheadpos = 0;
@@ -1466,6 +1579,15 @@ release_partition(WindowAggState *winstate)
tuplestore_clear(winstate->buffer);
winstate->partition_spooled = false;
winstate->next_partition = true;
+
+ /* Reset NFA state for new partition */
+ winstate->nfaContext = NULL;
+ winstate->nfaContextTail = NULL;
+ winstate->nfaContextFree = NULL;
+ winstate->nfaStateFree = NULL;
+ winstate->nfaLastProcessedRow = -1;
+ winstate->nfaStatesActive = 0;
+ winstate->nfaContextsActive = 0;
}
/*
@@ -2239,6 +2361,11 @@ ExecWindowAgg(PlanState *pstate)
CHECK_FOR_INTERRUPTS();
+#ifdef RPR_DEBUG
+ printf("ExecWindowAgg called. pos: " INT64_FORMAT "\n",
+ winstate->currentpos);
+#endif
+
if (winstate->status == WINDOWAGG_DONE)
return NULL;
@@ -2347,6 +2474,17 @@ ExecWindowAgg(PlanState *pstate)
/* don't evaluate the window functions when we're in pass-through mode */
if (winstate->status == WINDOWAGG_RUN)
{
+ /*
+ * If RPR is defined and skip mode is next row, we need to clear
+ * existing reduced frame info so that we newly calculate the info
+ * starting from current row.
+ */
+ if (rpr_is_defined(winstate))
+ {
+ if (winstate->rpSkipTo == ST_NEXT_ROW)
+ clear_reduced_frame_map(winstate);
+ }
+
/*
* Evaluate true window functions
*/
@@ -2513,6 +2651,9 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
TupleDesc scanDesc;
ListCell *l;
+ TargetEntry *te;
+ Expr *expr;
+
/* check for unsupported flags */
Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
@@ -2611,6 +2752,16 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
winstate->temp_slot_2 = ExecInitExtraTupleSlot(estate, scanDesc,
&TTSOpsMinimalTuple);
+ winstate->prev_slot = ExecInitExtraTupleSlot(estate, scanDesc,
+ &TTSOpsMinimalTuple);
+
+ winstate->next_slot = ExecInitExtraTupleSlot(estate, scanDesc,
+ &TTSOpsMinimalTuple);
+
+ winstate->null_slot = ExecInitExtraTupleSlot(estate, scanDesc,
+ &TTSOpsMinimalTuple);
+ winstate->null_slot = ExecStoreAllNullTuple(winstate->null_slot);
+
/*
* create frame head and tail slots only if needed (must create slots in
* exactly the same cases that update_frameheadpos and update_frametailpos
@@ -2797,6 +2948,71 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
winstate->inRangeAsc = node->inRangeAsc;
winstate->inRangeNullsFirst = node->inRangeNullsFirst;
+ /* Set up SKIP TO type */
+ winstate->rpSkipTo = node->rpSkipTo;
+ /* Set up row pattern recognition PATTERN clause (compiled NFA) */
+ winstate->rpPattern = node->rpPattern;
+
+ /* Calculate NFA state size and allocate cycle detection bitmap */
+ if (node->rpPattern != NULL)
+ {
+ winstate->nfaStateSize = offsetof(RPRNFAState, counts) +
+ sizeof(int32) * node->rpPattern->maxDepth;
+ winstate->nfaVisitedNWords =
+ (node->rpPattern->numElements - 1) / BITS_PER_BITMAPWORD + 1;
+ winstate->nfaVisitedElems = palloc0(sizeof(bitmapword) *
+ winstate->nfaVisitedNWords);
+ }
+
+ /* Set up row pattern recognition DEFINE clause */
+ winstate->defineVariableList = NIL;
+ winstate->defineClauseList = NIL;
+ if (node->defineClause != NIL)
+ {
+ /*
+ * Tweak arg var of PREV/NEXT so that it refers to scan/inner slot.
+ */
+ foreach(l, node->defineClause)
+ {
+ char *name;
+ ExprState *exps;
+
+ te = lfirst(l);
+ name = te->resname;
+ expr = te->expr;
+
+#ifdef RPR_DEBUG
+ printf("defineVariable name: %s\n", name);
+#endif
+ winstate->defineVariableList =
+ lappend(winstate->defineVariableList,
+ makeString(pstrdup(name)));
+ attno_map((Node *) expr);
+ exps = ExecInitExpr(expr, (PlanState *) winstate);
+ winstate->defineClauseList =
+ lappend(winstate->defineClauseList, exps);
+ }
+ }
+
+ /* Initialize NFA free lists for row pattern matching */
+ winstate->nfaContext = NULL;
+ winstate->nfaContextTail = NULL;
+ winstate->nfaContextFree = NULL;
+ winstate->nfaStateFree = NULL;
+ winstate->nfaLastProcessedRow = -1;
+ winstate->nfaStatesActive = 0;
+ winstate->nfaContextsActive = 0;
+
+ /*
+ * Allocate varMatched array for NFA evaluation. With the new varNames
+ * ordering (DEFINE order first), varId == defineIdx for all defined
+ * variables, so no mapping is needed.
+ */
+ if (list_length(winstate->defineVariableList) > 0)
+ winstate->nfaVarMatched = palloc0(sizeof(bool) *
+ list_length(winstate->defineVariableList));
+ else
+ winstate->nfaVarMatched = NULL;
winstate->all_first = true;
winstate->partition_spooled = false;
winstate->more_partitions = false;
@@ -2805,6 +3021,111 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
return winstate;
}
+/*
+ * Rewrite varno of Var nodes that are the argument of PREV/NET so that they
+ * see scan tuple (PREV) or inner tuple (NEXT). Also we check the arguments
+ * of PREV/NEXT include at least 1 column reference. This is required by the
+ * SQL standard.
+ */
+static void
+attno_map(Node *node)
+{
+ (void) expression_tree_walker(node, attno_map_walker, NULL);
+}
+
+static bool
+attno_map_walker(Node *node, void *context)
+{
+ FuncExpr *func;
+ int nargs;
+ bool is_prev;
+
+ if (node == NULL)
+ return false;
+
+ if (IsA(node, FuncExpr))
+ {
+ func = (FuncExpr *) node;
+
+ if (func->funcid == F_PREV || func->funcid == F_NEXT)
+ {
+ /*
+ * The SQL standard allows to have two more arguments form of
+ * PREV/NEXT. But currently we allow only 1 argument form.
+ */
+ nargs = list_length(func->args);
+ if (list_length(func->args) != 1)
+ elog(ERROR, "PREV/NEXT must have 1 argument but function %d has %d args",
+ func->funcid, nargs);
+
+ /*
+ * Check expr of PREV/NEXT aruguments and replace varno.
+ */
+ is_prev = (func->funcid == F_PREV) ? true : false;
+ check_rpr_navigation(node, is_prev);
+ }
+ }
+ return expression_tree_walker(node, attno_map_walker, NULL);
+}
+
+/*
+ * Rewrite varno of Var of RPR navigation operations (PREV/NEXT).
+ * If is_prev is true, we take care PREV, otherwise NEXT.
+ */
+static void
+check_rpr_navigation(Node *node, bool is_prev)
+{
+ NavigationInfo context;
+
+ context.is_prev = is_prev;
+ context.num_vars = 0;
+ (void) expression_tree_walker(node, rpr_navigation_walker, &context);
+ if (context.num_vars < 1)
+ ereport(ERROR,
+ errmsg("row pattern navigation operation's argument must include at least one column reference"));
+}
+
+static bool
+rpr_navigation_walker(Node *node, void *context)
+{
+ NavigationInfo *nav = (NavigationInfo *) context;
+
+ if (node == NULL)
+ return false;
+
+ switch (nodeTag(node))
+ {
+ case T_Var:
+ {
+ Var *var = (Var *) node;
+
+ nav->num_vars++;
+
+ if (nav->is_prev)
+ {
+ /*
+ * Rewrite varno from OUTER_VAR to regular var no so that
+ * the var references scan tuple.
+ */
+ var->varno = var->varnosyn;
+ }
+ else
+ var->varno = INNER_VAR;
+ }
+ break;
+ case T_Const:
+ case T_FuncExpr:
+ case T_OpExpr:
+ break;
+
+ default:
+ ereport(ERROR,
+ errmsg("row pattern navigation operation's argument includes unsupported expression"));
+ }
+ return expression_tree_walker(node, rpr_navigation_walker, context);
+}
+
+
/* -----------------
* ExecEndWindowAgg
* -----------------
@@ -2862,6 +3183,8 @@ ExecReScanWindowAgg(WindowAggState *node)
ExecClearTuple(node->agg_row_slot);
ExecClearTuple(node->temp_slot_1);
ExecClearTuple(node->temp_slot_2);
+ ExecClearTuple(node->prev_slot);
+ ExecClearTuple(node->next_slot);
if (node->framehead_slot)
ExecClearTuple(node->framehead_slot);
if (node->frametail_slot)
@@ -3222,7 +3545,8 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
return false;
if (pos < winobj->markpos)
- elog(ERROR, "cannot fetch row before WindowObject's mark position");
+ elog(ERROR, "cannot fetch row: " INT64_FORMAT " before WindowObject's mark position: " INT64_FORMAT,
+ pos, winobj->markpos);
oldcontext = MemoryContextSwitchTo(winstate->ss.ps.ps_ExprContext->ecxt_per_query_memory);
@@ -3339,6 +3663,7 @@ ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
int notnull_offset;
int notnull_relpos;
int forward;
+ int num_reduced_frame;
Assert(WindowObjectIsValid(winobj));
winstate = winobj->winstate;
@@ -3367,6 +3692,13 @@ ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
/* rejecting relpos > 0 is easy and simplifies code below */
if (relpos > 0)
goto out_of_frame;
+
+ /*
+ * RPR cares about frame head pos. Need to call
+ * update_frameheadpos
+ */
+ update_frameheadpos(winstate);
+
update_frametailpos(winstate);
abs_pos = winstate->frametailpos - 1;
mark_pos = 0; /* keep compiler quiet */
@@ -3382,6 +3714,35 @@ ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
* Get the next nonnull value in the frame, moving forward or backward
* until we find a value or reach the frame's end.
*/
+
+ /*
+ * Check whether current row is in reduced frame.
+ */
+ num_reduced_frame = row_is_in_reduced_frame(winobj, winstate->frameheadpos);
+ if (num_reduced_frame < 0) /* unmatched or skipped row */
+ goto out_of_frame;
+ else if (num_reduced_frame > 0) /* the first row of the reduced frame */
+ {
+ /*
+ * Early check if row could be out of reduced frame. When RPR is
+ * enabled, EXCUDE clause cannot be specified and the frame is always
+ * contiguous. So we can do the check followings safely. Note,
+ * however, it is possible that a row is out of reduced frame if
+ * there's a NULL in the middle. So we need to check it in the
+ * following do lopp.
+ */
+ if (seektype == WINDOW_SEEK_HEAD && relpos >= num_reduced_frame)
+ goto out_of_frame;
+ if (seektype == WINDOW_SEEK_TAIL)
+ {
+ if (notnull_relpos >= num_reduced_frame)
+ goto out_of_frame;
+
+ /* not out of reduced frame. Set abspos as a starting point */
+ abs_pos = winstate->frameheadpos + num_reduced_frame - 1;
+ }
+ }
+
do
{
int inframe;
@@ -3443,6 +3804,16 @@ ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
}
advance:
abs_pos += forward;
+ if (rpr_is_defined(winstate))
+ {
+ /*
+ * Check whether we are still in the reduced frame. (also check
+ * if we succeeded in getting the target row).
+ */
+ num_reduced_frame--;
+ if (num_reduced_frame <= 0 && notnull_offset <= notnull_relpos)
+ goto out_of_frame;
+ }
} while (notnull_offset <= notnull_relpos);
if (set_mark)
@@ -3564,6 +3935,407 @@ put_notnull_info(WindowObject winobj, int64 pos, int argno, bool isnull)
mbp[bpos] = mb;
}
+/*
+ * rpr_is_defined
+ * return true if Row pattern recognition is defined.
+ */
+static bool
+rpr_is_defined(WindowAggState *winstate)
+{
+ return winstate->rpPattern != NULL;
+}
+
+/*
+ * -----------------
+ * row_is_in_reduced_frame
+ * Determine whether a row is in the current row's reduced window frame
+ * according to row pattern matching
+ *
+ * The row must has been already determined that it is in a full window frame
+ * and fetched it into slot.
+ *
+ * Returns:
+ * = 0, RPR is not defined.
+ * >0, if the row is the first in the reduced frame. Return the number of rows
+ * in the reduced frame.
+ * -1, if the row is unmatched row
+ * -2, if the row is in the reduced frame but needed to be skipped because of
+ * AFTER MATCH SKIP PAST LAST ROW
+ * -----------------
+ */
+static int
+row_is_in_reduced_frame(WindowObject winobj, int64 pos)
+{
+ WindowAggState *winstate = winobj->winstate;
+ int state;
+ int rtn;
+
+ if (!rpr_is_defined(winstate))
+ {
+ /*
+ * RPR is not defined. Assume that we are always in the the reduced
+ * window frame.
+ */
+ rtn = 0;
+#ifdef RPR_DEBUG
+ printf("row_is_in_reduced_frame returns %d: pos: " INT64_FORMAT "\n",
+ rtn, pos);
+#endif
+ return rtn;
+ }
+
+ state = get_reduced_frame_map(winstate, pos);
+
+ if (state == RF_NOT_DETERMINED)
+ {
+ update_frameheadpos(winstate);
+ update_reduced_frame(winobj, pos);
+ }
+
+ state = get_reduced_frame_map(winstate, pos);
+
+ switch (state)
+ {
+ int64 i;
+ int num_reduced_rows;
+
+ case RF_FRAME_HEAD:
+ num_reduced_rows = 1;
+ for (i = pos + 1;
+ get_reduced_frame_map(winstate, i) == RF_SKIPPED; i++)
+ num_reduced_rows++;
+ rtn = num_reduced_rows;
+ break;
+
+ case RF_SKIPPED:
+ rtn = -2;
+ break;
+
+ case RF_UNMATCHED:
+ rtn = -1;
+ break;
+
+ default:
+ elog(ERROR, "unrecognized state: %d at: " INT64_FORMAT,
+ state, pos);
+ break;
+ }
+
+#ifdef RPR_DEBUG
+ printf("row_is_in_reduced_frame returns %d: pos: " INT64_FORMAT "\n",
+ rtn, pos);
+#endif
+ return rtn;
+}
+
+#define REDUCED_FRAME_MAP_INIT_SIZE 1024L
+
+/*
+ * create_reduced_frame_map
+ * Create reduced frame map
+ */
+static void
+create_reduced_frame_map(WindowAggState *winstate)
+{
+ winstate->reduced_frame_map =
+ MemoryContextAlloc(winstate->partcontext,
+ REDUCED_FRAME_MAP_INIT_SIZE);
+ winstate->alloc_sz = REDUCED_FRAME_MAP_INIT_SIZE;
+ clear_reduced_frame_map(winstate);
+}
+
+/*
+ * clear_reduced_frame_map
+ * Clear reduced frame map
+ */
+static void
+clear_reduced_frame_map(WindowAggState *winstate)
+{
+ Assert(winstate->reduced_frame_map != NULL);
+ MemSet(winstate->reduced_frame_map, RF_NOT_DETERMINED,
+ winstate->alloc_sz);
+}
+
+/*
+ * get_reduced_frame_map
+ * Get reduced frame map specified by pos
+ */
+static int
+get_reduced_frame_map(WindowAggState *winstate, int64 pos)
+{
+ Assert(winstate->reduced_frame_map != NULL);
+ Assert(pos >= 0);
+
+ /*
+ * If pos is not in the reduced frame map, it means that any info
+ * regarding the pos has not been registered yet. So we return
+ * RF_NOT_DETERMINED.
+ */
+ if (pos >= winstate->alloc_sz)
+ return RF_NOT_DETERMINED;
+
+ return winstate->reduced_frame_map[pos];
+}
+
+/*
+ * register_reduced_frame_map
+ * Add/replace reduced frame map member at pos.
+ * If there's no enough space, expand the map.
+ */
+static void
+register_reduced_frame_map(WindowAggState *winstate, int64 pos, int val)
+{
+ int64 realloc_sz;
+
+ Assert(winstate->reduced_frame_map != NULL);
+
+ if (pos < 0)
+ elog(ERROR, "wrong pos: " INT64_FORMAT, pos);
+
+ while (pos > winstate->alloc_sz - 1)
+ {
+ realloc_sz = winstate->alloc_sz * 2;
+
+ winstate->reduced_frame_map =
+ repalloc(winstate->reduced_frame_map, realloc_sz);
+
+ MemSet(winstate->reduced_frame_map + winstate->alloc_sz,
+ RF_NOT_DETERMINED, realloc_sz - winstate->alloc_sz);
+
+ winstate->alloc_sz = realloc_sz;
+ }
+
+ winstate->reduced_frame_map[pos] = val;
+}
+
+/*
+ * update_reduced_frame
+ * Update reduced frame info using multi-context NFA pattern matching.
+ *
+ * Maintains multiple NFA contexts simultaneously, one for each potential
+ * match start position. This allows sharing row evaluations across contexts,
+ * avoiding redundant DEFINE clause evaluations when rewinding for SKIP TO
+ * NEXT ROW mode.
+ *
+ * Key optimizations:
+ * - Row evaluations (expensive DEFINE clauses) happen only once per row
+ * - All active contexts share the same evaluation results
+ * - Contexts persist across calls, enabling O(n) DEFINE evaluations
+ */
+static void
+update_reduced_frame(WindowObject winobj, int64 pos)
+{
+ WindowAggState *winstate = winobj->winstate;
+ RPRNFAContext *targetCtx;
+ int64 currentPos;
+ int64 startPos;
+ int frameOptions = winstate->frameOptions;
+ bool hasLimitedFrame;
+ int64 frameOffset = 0;
+ int64 matchLen;
+
+ /*
+ * Check if we have a limited frame (ROWS ... N FOLLOWING). Each context
+ * needs its own frame end based on matchStartRow + offset.
+ */
+ hasLimitedFrame = (frameOptions & FRAMEOPTION_ROWS) &&
+ !(frameOptions & FRAMEOPTION_END_UNBOUNDED_FOLLOWING);
+ if (hasLimitedFrame && winstate->endOffsetValue != 0)
+ frameOffset = DatumGetInt64(winstate->endOffsetValue);
+
+ /*
+ * Case 1: pos is before any existing context's start position. This means
+ * the position was already processed and determined unmatched. Head is
+ * the oldest context (lowest matchStartRow) since contexts are added at
+ * tail with increasing positions.
+ */
+ if (winstate->nfaContext != NULL &&
+ pos < winstate->nfaContext->matchStartRow)
+ {
+ register_reduced_frame_map(winstate, pos, RF_UNMATCHED);
+ return;
+ }
+
+ /*
+ * Case 2: Find existing context for this pos, or create new one.
+ */
+ targetCtx = ExecRPRGetHeadContext(winstate, pos);
+ if (targetCtx == NULL)
+ {
+ /*
+ * No context exists. If pos is already processed, it means this row
+ * was already determined to be unmatched or skipped - no need to
+ * reprocess.
+ */
+ if (pos <= winstate->nfaLastProcessedRow)
+ {
+ register_reduced_frame_map(winstate, pos, RF_UNMATCHED);
+ return;
+ }
+ /* Not yet processed - create new context and start fresh */
+ targetCtx = ExecRPRStartContext(winstate, pos);
+ }
+ else if (targetCtx->states == NULL)
+ {
+ /* Context already completed - skip to result registration */
+ goto register_result;
+ }
+
+ /*
+ * Determine where to start processing. Usually nfaLastProcessedRow+1 >=
+ * pos since contexts are created at currentPos+1 during processing.
+ * However, pos can exceed this when rows are skipped (e.g., unmatched
+ * rows don't update nfaLastProcessedRow).
+ */
+ startPos = Max(pos, winstate->nfaLastProcessedRow + 1);
+
+ /*
+ * Process rows until target context completes or we hit boundaries. Each
+ * row evaluation is shared across all active contexts.
+ */
+ for (currentPos = startPos; targetCtx->states != NULL; currentPos++)
+ {
+ bool rowExists;
+
+ /*
+ * Evaluate variables for this row - done only once, shared by all
+ * contexts
+ */
+ rowExists = nfa_evaluate_row(winobj, currentPos, winstate->nfaVarMatched);
+
+ /* No more rows in partition? Finalize all contexts */
+ if (!rowExists)
+ {
+ ExecRPRFinalizeAllContexts(winstate, currentPos - 1);
+ /* Clean up dead contexts from finalization */
+ ExecRPRCleanupDeadContexts(winstate, targetCtx);
+ break;
+ }
+
+ /* Update last processed row */
+ winstate->nfaLastProcessedRow = currentPos;
+
+ /*--------------------------
+ * Process all contexts for this row:
+ * 1. Match all (convergence)
+ * 2. Absorb redundant
+ * 3. Advance all (divergence)
+ */
+ ExecRPRProcessRow(winstate, currentPos, hasLimitedFrame, frameOffset);
+
+ /*
+ * Create a new context for the next potential start position. This
+ * enables overlapping match detection for SKIP TO NEXT ROW.
+ */
+ ExecRPRStartContext(winstate, currentPos + 1);
+
+ /*
+ * Clean up dead contexts (failed with no active states and no match).
+ * This removes contexts that failed during processing and counts them
+ * appropriately as pruned or mismatched.
+ */
+ ExecRPRCleanupDeadContexts(winstate, targetCtx);
+ }
+
+register_result:
+ Assert(pos == targetCtx->matchStartRow);
+
+ /*
+ * Register reduced frame map based on match result.
+ */
+ if (targetCtx->matchEndRow < targetCtx->matchStartRow)
+ {
+ matchLen = targetCtx->lastProcessedRow - targetCtx->matchStartRow + 1;
+
+ register_reduced_frame_map(winstate, targetCtx->matchStartRow, RF_UNMATCHED);
+ ExecRPRRecordContextFailure(winstate, matchLen);
+ ExecRPRFreeContext(winstate, targetCtx);
+ return;
+ }
+
+ /* Match succeeded - register frame map and record statistics */
+ matchLen = targetCtx->matchEndRow - targetCtx->matchStartRow + 1;
+
+ register_reduced_frame_map(winstate, targetCtx->matchStartRow, RF_FRAME_HEAD);
+ for (int64 i = targetCtx->matchStartRow + 1; i <= targetCtx->matchEndRow; i++)
+ {
+ register_reduced_frame_map(winstate, i, RF_SKIPPED);
+ }
+ ExecRPRRecordContextSuccess(winstate, matchLen);
+
+ /* Remove the matched context */
+ ExecRPRFreeContext(winstate, targetCtx);
+}
+
+/*
+ * nfa_evaluate_row
+ *
+ * Evaluate all DEFINE variables for current row.
+ * Returns true if the row exists, false if out of partition.
+ * If row exists, fills varMatched array.
+ * varMatched[i] = true if variable i matched at current row.
+ */
+static bool
+nfa_evaluate_row(WindowObject winobj, int64 pos, bool *varMatched)
+{
+ WindowAggState *winstate = winobj->winstate;
+ ExprContext *econtext = winstate->ss.ps.ps_ExprContext;
+ int numDefineVars = list_length(winstate->defineVariableList);
+ ListCell *lc;
+ int varIdx = 0;
+ TupleTableSlot *slot;
+
+ /*
+ * Set up slots for current, previous, and next rows. We don't call
+ * get_slots() here to avoid recursion through row_is_in_frame ->
+ * update_reduced_frame -> ExecRPRProcessRow.
+ */
+
+ /* Current row -> ecxt_outertuple */
+ slot = winstate->temp_slot_1;
+ if (!window_gettupleslot(winobj, pos, slot))
+ return false; /* No row exists */
+ econtext->ecxt_outertuple = slot;
+
+ /* Previous row -> ecxt_scantuple (for PREV) */
+ if (pos > 0)
+ {
+ slot = winstate->prev_slot;
+ if (!window_gettupleslot(winobj, pos - 1, slot))
+ econtext->ecxt_scantuple = winstate->null_slot;
+ else
+ econtext->ecxt_scantuple = slot;
+ }
+ else
+ econtext->ecxt_scantuple = winstate->null_slot;
+
+ /* Next row -> ecxt_innertuple (for NEXT) */
+ slot = winstate->next_slot;
+ if (!window_gettupleslot(winobj, pos + 1, slot))
+ econtext->ecxt_innertuple = winstate->null_slot;
+ else
+ econtext->ecxt_innertuple = slot;
+
+ foreach(lc, winstate->defineClauseList)
+ {
+ ExprState *exprState = (ExprState *) lfirst(lc);
+ Datum result;
+ bool isnull;
+
+ /* Evaluate DEFINE expression */
+ result = ExecEvalExpr(exprState, econtext, &isnull);
+
+ varMatched[varIdx] = (!isnull && DatumGetBool(result));
+
+ varIdx++;
+ if (varIdx >= numDefineVars)
+ break;
+ }
+
+ return true; /* Row exists */
+}
+
+
/***********************************************************************
* API exposed to window functions
***********************************************************************/
@@ -3924,8 +4696,6 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
WindowAggState *winstate;
ExprContext *econtext;
TupleTableSlot *slot;
- int64 abs_pos;
- int64 mark_pos;
Assert(WindowObjectIsValid(winobj));
winstate = winobj->winstate;
@@ -3936,6 +4706,48 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
set_mark, isnull, isout);
+ if (WinGetSlotInFrame(winobj, slot,
+ relpos, seektype, set_mark,
+ isnull, isout) == 0)
+ {
+ econtext->ecxt_outertuple = slot;
+ return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+ econtext, isnull);
+ }
+
+ if (isout)
+ *isout = true;
+ *isnull = true;
+ return (Datum) 0;
+}
+
+/*
+ * WinGetSlotInFrame
+ * slot: TupleTableSlot to store the result
+ * relpos: signed rowcount offset from the seek position
+ * seektype: WINDOW_SEEK_HEAD or WINDOW_SEEK_TAIL
+ * set_mark: If the row is found/in frame and set_mark is true, the mark is
+ * moved to the row as a side-effect.
+ * isnull: output argument, receives isnull status of result
+ * isout: output argument, set to indicate whether target row position
+ * is out of frame (can pass NULL if caller doesn't care about this)
+ *
+ * Returns 0 if we successfullt got the slot. false if out of frame.
+ * (also isout is set)
+ */
+static int
+WinGetSlotInFrame(WindowObject winobj, TupleTableSlot *slot,
+ int relpos, int seektype, bool set_mark,
+ bool *isnull, bool *isout)
+{
+ WindowAggState *winstate;
+ int64 abs_pos;
+ int64 mark_pos;
+ int num_reduced_frame;
+
+ Assert(WindowObjectIsValid(winobj));
+ winstate = winobj->winstate;
+
switch (seektype)
{
case WINDOW_SEEK_CURRENT:
@@ -4002,11 +4814,25 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
winstate->frameOptions);
break;
}
+ num_reduced_frame = row_is_in_reduced_frame(winobj,
+ winstate->frameheadpos);
+ if (num_reduced_frame < 0)
+ goto out_of_frame;
+ else if (num_reduced_frame > 0)
+ if (relpos >= num_reduced_frame)
+ goto out_of_frame;
break;
case WINDOW_SEEK_TAIL:
/* rejecting relpos > 0 is easy and simplifies code below */
if (relpos > 0)
goto out_of_frame;
+
+ /*
+ * RPR cares about frame head pos. Need to call
+ * update_frameheadpos
+ */
+ update_frameheadpos(winstate);
+
update_frametailpos(winstate);
abs_pos = winstate->frametailpos - 1 + relpos;
@@ -4073,6 +4899,14 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
mark_pos = 0; /* keep compiler quiet */
break;
}
+
+ num_reduced_frame = row_is_in_reduced_frame(winobj,
+ winstate->frameheadpos + relpos);
+ if (num_reduced_frame < 0)
+ goto out_of_frame;
+ else if (num_reduced_frame > 0)
+ abs_pos = winstate->frameheadpos + relpos +
+ num_reduced_frame - 1;
break;
default:
elog(ERROR, "unrecognized window seek type: %d", seektype);
@@ -4091,15 +4925,13 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
*isout = false;
if (set_mark)
WinSetMarkPosition(winobj, mark_pos);
- econtext->ecxt_outertuple = slot;
- return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
- econtext, isnull);
+ return 0;
out_of_frame:
if (isout)
*isout = true;
*isnull = true;
- return (Datum) 0;
+ return -1;
}
/*
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index 78b7f05aba2..efb60c99052 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -41,7 +41,6 @@ static bool rank_up(WindowObject winobj);
static Datum leadlag_common(FunctionCallInfo fcinfo,
bool forward, bool withoffset, bool withdefault);
-
/*
* utility routine for *_rank functions.
*/
@@ -683,7 +682,7 @@ window_last_value(PG_FUNCTION_ARGS)
WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
result = WinGetFuncArgInFrame(winobj, 0,
- 0, WINDOW_SEEK_TAIL, true,
+ 0, WINDOW_SEEK_TAIL, false,
&isnull, NULL);
if (isnull)
PG_RETURN_NULL();
@@ -724,3 +723,25 @@ window_nth_value(PG_FUNCTION_ARGS)
PG_RETURN_DATUM(result);
}
+
+/*
+ * prev
+ * Dummy function to invoke RPR's navigation operator "PREV".
+ * This is *not* a window function.
+ */
+Datum
+window_prev(PG_FUNCTION_ARGS)
+{
+ PG_RETURN_DATUM(PG_GETARG_DATUM(0));
+}
+
+/*
+ * next
+ * Dummy function to invoke RPR's navigation operation "NEXT".
+ * This is *not* a window function.
+ */
+Datum
+window_next(PG_FUNCTION_ARGS)
+{
+ PG_RETURN_DATUM(PG_GETARG_DATUM(0));
+}
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index fc8d82665b8..a16457124c9 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -10957,6 +10957,12 @@
{ oid => '3114', descr => 'fetch the Nth row value',
proname => 'nth_value', prokind => 'w', prorettype => 'anyelement',
proargtypes => 'anyelement int4', prosrc => 'window_nth_value' },
+{ oid => '8126', descr => 'previous value',
+ proname => 'prev', provolatile => 's', prorettype => 'anyelement',
+ proargtypes => 'anyelement', prosrc => 'window_prev' },
+{ oid => '8127', descr => 'next value',
+ proname => 'next', provolatile => 's', prorettype => 'anyelement',
+ proargtypes => 'anyelement', prosrc => 'window_next' },
# functions for range types
{ oid => '3832', descr => 'I/O',
diff --git a/src/include/executor/execRPR.h b/src/include/executor/execRPR.h
new file mode 100644
index 00000000000..7b2b0febb76
--- /dev/null
+++ b/src/include/executor/execRPR.h
@@ -0,0 +1,40 @@
+/*-------------------------------------------------------------------------
+ *
+ * execRPR.h
+ * prototypes for execRPR.c (NFA-based Row Pattern Recognition engine)
+ *
+ *
+ * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/executor/execRPR.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef EXECRPR_H
+#define EXECRPR_H
+
+#include "nodes/execnodes.h"
+#include "windowapi.h"
+
+/* NFA context management */
+extern RPRNFAContext *ExecRPRStartContext(WindowAggState *winstate,
+ int64 startPos);
+extern RPRNFAContext *ExecRPRGetHeadContext(WindowAggState *winstate,
+ int64 pos);
+extern void ExecRPRFreeContext(WindowAggState *winstate, RPRNFAContext *ctx);
+
+/* NFA processing */
+extern void ExecRPRProcessRow(WindowAggState *winstate, int64 currentPos,
+ bool hasLimitedFrame, int64 frameOffset);
+extern void ExecRPRCleanupDeadContexts(WindowAggState *winstate,
+ RPRNFAContext *excludeCtx);
+extern void ExecRPRFinalizeAllContexts(WindowAggState *winstate, int64 lastPos);
+
+/* NFA statistics */
+extern void ExecRPRRecordContextSuccess(WindowAggState *winstate,
+ int64 matchLen);
+extern void ExecRPRRecordContextFailure(WindowAggState *winstate,
+ int64 failedLen);
+
+#endif /* EXECRPR_H */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 0716c5a9aed..ff4f79be104 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -38,6 +38,9 @@
#include "nodes/plannodes.h"
#include "partitioning/partdefs.h"
#include "storage/buf.h"
+#include "storage/condition_variable.h"
+#include "utils/hsearch.h"
+#include "utils/queryenvironment.h"
#include "utils/reltrigger.h"
@@ -2491,6 +2494,69 @@ typedef enum WindowAggStatus
* tuples during spool */
} WindowAggStatus;
+#define RF_NOT_DETERMINED 0
+#define RF_FRAME_HEAD 1
+#define RF_SKIPPED 2
+#define RF_UNMATCHED 3
+
+/*
+ * RPRNFAState - single NFA state for pattern matching
+ *
+ * counts[] tracks repetition counts at each nesting depth.
+ *
+ * isAbsorbable tracks if state is in absorbable region (ABSORBABLE_BRANCH).
+ * Monotonic property: once false, stays false (can't re-enter region).
+ */
+typedef struct RPRNFAState
+{
+ struct RPRNFAState *next; /* next state in linked list */
+ int16 elemIdx; /* current pattern element index */
+ bool isAbsorbable; /* true if state is in absorbable region */
+ int32 counts[FLEXIBLE_ARRAY_MEMBER]; /* repetition counts by depth */
+} RPRNFAState;
+
+/*
+ * RPRNFAContext - context for NFA pattern matching execution
+ *
+ * Two-flag absorption design:
+ * hasAbsorbableState: can this context absorb others? (>=1 absorbable state)
+ * - Monotonic: true->false only, cannot recover once false
+ * - Used to skip absorption attempts once all absorbable states are gone
+ * allStatesAbsorbable: can this context be absorbed? (ALL states absorbable)
+ * - Dynamic: can change false->true (when non-absorbable states die)
+ * - Used to determine if this context is eligible for absorption
+ */
+typedef struct RPRNFAContext
+{
+ struct RPRNFAContext *next; /* next context in linked list */
+ struct RPRNFAContext *prev; /* previous context (for reverse traversal) */
+ RPRNFAState *states; /* active states (linked list) */
+
+ int64 matchStartRow; /* row where match started */
+ int64 matchEndRow; /* row where match ended (-1 = no match) */
+ int64 lastProcessedRow; /* last row processed (for fail depth) */
+ RPRNFAState *matchedState; /* FIN state for greedy fallback (cloned) */
+
+ /* Two-flag absorption optimization */
+ bool hasAbsorbableState; /* can absorb others (>=1 absorbable
+ * state) */
+ bool allStatesAbsorbable; /* can be absorbed (ALL states
+ * absorbable) */
+} RPRNFAContext;
+
+/*
+ * NFALengthStats
+ *
+ * Statistics for length measurements (min/max/total) used for computing
+ * average lengths in EXPLAIN ANALYZE output.
+ */
+typedef struct NFALengthStats
+{
+ int64 min; /* minimum length */
+ int64 max; /* maximum length */
+ int64 total; /* total length (for computing average) */
+} NFALengthStats;
+
typedef struct WindowAggState
{
ScanState ss; /* its first field is NodeTag */
@@ -2550,6 +2616,46 @@ typedef struct WindowAggState
int64 groupheadpos; /* current row's peer group head position */
int64 grouptailpos; /* " " " " tail position (group end+1) */
+ /* these fields are used in Row pattern recognition: */
+ RPSkipTo rpSkipTo; /* Row Pattern Skip To type */
+ struct RPRPattern *rpPattern; /* compiled pattern for NFA execution */
+ List *defineVariableList; /* list of row pattern definition
+ * variables (list of String) */
+ List *defineClauseList; /* expression for row pattern definition
+ * search conditions ExprState list */
+ RPRNFAContext *nfaContext; /* active matching contexts (head) */
+ RPRNFAContext *nfaContextTail; /* tail of active contexts (for reverse
+ * traversal) */
+ RPRNFAContext *nfaContextFree; /* recycled NFA context nodes */
+ RPRNFAState *nfaStateFree; /* recycled NFA state nodes */
+ Size nfaStateSize; /* pre-calculated RPRNFAState size */
+ bool *nfaVarMatched; /* per-row cache: varMatched[varId] for varId
+ * < numDefines */
+ bitmapword *nfaVisitedElems; /* elemIdx visited bitmap for cycle
+ * detection */
+ int nfaVisitedNWords; /* number of bitmapwords in
+ * nfaVisitedElems */
+ int64 nfaLastProcessedRow; /* last row processed by NFA (-1 =
+ * none) */
+
+ /* NFA statistics for EXPLAIN ANALYZE */
+ int64 nfaStatesActive; /* current active states (internal) */
+ int64 nfaStatesMax; /* peak active states */
+ int64 nfaStatesTotalCreated; /* total states allocated */
+ int64 nfaStatesMerged; /* states merged (deduplicated) */
+ int64 nfaContextsActive; /* current active contexts (internal) */
+ int64 nfaContextsMax; /* peak active contexts */
+ int64 nfaContextsTotalCreated; /* total contexts allocated */
+ int64 nfaContextsAbsorbed; /* contexts absorbed (optimization) */
+ int64 nfaContextsSkipped; /* contexts skipped (SKIP PAST LAST ROW) */
+ int64 nfaContextsPruned; /* contexts pruned on first row */
+ int64 nfaMatchesSucceeded; /* successful pattern matches */
+ int64 nfaMatchesFailed; /* failed pattern matches */
+ NFALengthStats nfaMatchLen; /* successful match length stats */
+ NFALengthStats nfaFailLen; /* mismatch length stats */
+ NFALengthStats nfaAbsorbedLen; /* absorbed context length stats */
+ NFALengthStats nfaSkippedLen; /* skipped context length stats */
+
MemoryContext partcontext; /* context for partition-lifespan data */
MemoryContext aggcontext; /* shared context for aggregate working data */
MemoryContext curaggcontext; /* current aggregate's working data */
@@ -2577,6 +2683,18 @@ typedef struct WindowAggState
TupleTableSlot *agg_row_slot;
TupleTableSlot *temp_slot_1;
TupleTableSlot *temp_slot_2;
+
+ /* temporary slots for RPR */
+ TupleTableSlot *prev_slot; /* PREV row navigation operator */
+ TupleTableSlot *next_slot; /* NEXT row navigation operator */
+ TupleTableSlot *null_slot; /* all NULL slot */
+
+ /*
+ * Each byte corresponds to a row positioned at absolute its pos in
+ * partition. See above definition for RF_*. Used for RPR.
+ */
+ char *reduced_frame_map;
+ int64 alloc_sz; /* size of the map */
} WindowAggState;
/* ----------------
--
2.43.0