v19-0004-Allow-MergeAppend-s-subnodes-to-be-pruned-during.patch

From 221cfd2e067cda6dc13dda3b0c0627bfd215f0fb Mon Sep 17 00:00:00 2001
From: "dgrowley@gmail.com" <dgrowley@gmail.com>
Date: Thu, 5 Apr 2018 11:57:58 +1200
Subject: [PATCH v19 4/5] Allow MergeAppend's subnodes to be pruned during
 execution

Already supported for Append nodes, this commit allows partition pruning to
occur in MergeAppend using values which are only known during execution.
---
 src/backend/executor/nodeMergeAppend.c        | 136 ++++++++++++++++++++----
 src/backend/nodes/copyfuncs.c                 |   1 +
 src/backend/nodes/outfuncs.c                  |   2 +
 src/backend/nodes/readfuncs.c                 |   1 +
 src/backend/optimizer/plan/createplan.c       |  34 ++++++
 src/include/nodes/execnodes.h                 |   9 ++
 src/include/nodes/plannodes.h                 |   4 +
 src/test/regress/expected/partition_prune.out | 145 ++++++++++++++++++++++++++
 src/test/regress/sql/partition_prune.sql      |  41 ++++++++
 9 files changed, 351 insertions(+), 22 deletions(-)

diff --git a/src/backend/executor/nodeMergeAppend.c b/src/backend/executor/nodeMergeAppend.c
index 118f4ef07d..d9cf911f4f 100644
--- a/src/backend/executor/nodeMergeAppend.c
+++ b/src/backend/executor/nodeMergeAppend.c
@@ -39,6 +39,7 @@
 #include "postgres.h"
 
 #include "executor/execdebug.h"
+#include "executor/execPartition.h"
 #include "executor/nodeMergeAppend.h"
 #include "lib/binaryheap.h"
 #include "miscadmin.h"
@@ -65,8 +66,9 @@ ExecInitMergeAppend(MergeAppend *node, EState *estate, int eflags)
 {
 	MergeAppendState *mergestate = makeNode(MergeAppendState);
 	PlanState **mergeplanstates;
+	Bitmapset  *validsubplans;
 	int			nplans;
-	int			i;
+	int			i, j;
 	ListCell   *lc;
 
 	/* check for unsupported flags */
@@ -78,19 +80,89 @@ ExecInitMergeAppend(MergeAppend *node, EState *estate, int eflags)
 	 */
 	ExecLockNonLeafAppendTables(node->partitioned_rels, estate);
 
-	/*
-	 * Set up empty vector of subplan states
-	 */
-	nplans = list_length(node->mergeplans);
-
-	mergeplanstates = (PlanState **) palloc0(nplans * sizeof(PlanState *));
-
 	/*
 	 * create new MergeAppendState for our node
 	 */
 	mergestate->ps.plan = (Plan *) node;
 	mergestate->ps.state = estate;
 	mergestate->ps.ExecProcNode = ExecMergeAppend;
+	mergestate->ms_noopscan = false;
+
+	/* If run-time partition pruning is enabled, then setup that up now */
+	if (node->part_prune_infos != NIL)
+	{
+		PartitionPruning *partprune;
+
+		ExecAssignExprContext(estate, &mergestate->ps);
+
+		partprune = ExecSetupPartitionPruning(&mergestate->ps,
+											  node->part_prune_infos);
+
+		/*
+		 * When there are external params matching the partition key we may be
+		 * able to prune away MergeAppend subplans now.
+		 */
+		if (!bms_is_empty(partprune->extparams))
+		{
+			/* Determine which subplans match the external params */
+			validsubplans = ExecFindInitialMatchingSubPlans(partprune,
+											list_length(node->mergeplans));
+
+			/*
+			 * If no subplans match the given parameters then we must handle
+			 * this case in a special way.  The problem here is that code in
+			 * explain.c requires a MergeAppend to have at least one subplan
+			 * in order for it to properly determine the Vars in that
+			 * subplan's targetlist.  We sidestep this issue by just
+			 * initializing the first subplan, but we set a noop flag so that
+			 * we never actually bother scanning it.
+			 */
+			if (bms_is_empty(validsubplans))
+			{
+				mergestate->ms_noopscan = true;
+
+				/* Mark the first as valid so that it's initialized below */
+				validsubplans = bms_make_singleton(0);
+			}
+
+			nplans = bms_num_members(validsubplans);
+		}
+		else
+		{
+			/* We'll need to initialize all subplans */
+			nplans = list_length(node->mergeplans);
+			validsubplans = bms_add_range(NULL, 0, nplans - 1);
+		}
+
+		/*
+		 * If there are no exec params then no further pruning can be done, we
+		 * can just set the valid subplans to all remaining subplans.
+		 * Otherwise we set the valid subplans to NULL so that they can be
+		 * determined during actual execution.
+		 */
+		if (bms_is_empty(partprune->execparams))
+			mergestate->ms_valid_subplans = bms_add_range(NULL, 0, nplans - 1);
+		else
+			mergestate->ms_valid_subplans = NULL;
+
+
+		mergestate->partition_pruning = partprune;
+
+	}
+	else
+	{
+		nplans = list_length(node->mergeplans);
+
+		/*
+		 * When run-time partition pruning is not enabled we can just mark
+		 * all subplans as valid.
+		 */
+		mergestate->ms_valid_subplans = validsubplans =
+							bms_add_range(NULL, 0, nplans - 1);
+		mergestate->partition_pruning = NULL;
+	}
+
+	mergeplanstates = (PlanState **) palloc(nplans * sizeof(PlanState *));
 	mergestate->mergeplans = mergeplanstates;
 	mergestate->ms_nplans = nplans;
 
@@ -101,26 +173,23 @@ ExecInitMergeAppend(MergeAppend *node, EState *estate, int eflags)
 	/*
 	 * Miscellaneous initialization
 	 *
-	 * MergeAppend plans don't have expression contexts because they never
-	 * call ExecQual or ExecProject.
-	 */
-
-	/*
 	 * MergeAppend nodes do have Result slots, which hold pointers to tuples,
 	 * so we have to initialize them.
 	 */
 	ExecInitResultTupleSlotTL(estate, &mergestate->ps);
 
 	/*
-	 * call ExecInitNode on each of the plans to be executed and save the
-	 * results into the array "mergeplans".
+	 * call ExecInitNode on each of the valid plans to be executed and save
+	 * the results into the mergeplanstates array.
 	 */
-	i = 0;
+	j = i = 0;
 	foreach(lc, node->mergeplans)
 	{
-		Plan	   *initNode = (Plan *) lfirst(lc);
-
-		mergeplanstates[i] = ExecInitNode(initNode, estate, eflags);
+		if (bms_is_member(i, validsubplans))
+		{
+			Plan	   *initNode = (Plan *) lfirst(lc);
+			mergeplanstates[j++] = ExecInitNode(initNode, estate, eflags);
+		}
 		i++;
 	}
 
@@ -178,11 +247,21 @@ ExecMergeAppend(PlanState *pstate)
 
 	if (!node->ms_initialized)
 	{
+		/* Handle the case for when all subplans were pruned */
+		if (node->ms_noopscan)
+			return ExecClearTuple(node->ps.ps_ResultTupleSlot);
+
+		/* Determine minimum set of matching partitions, if not already set */
+		if (node->ms_valid_subplans == NULL)
+			node->ms_valid_subplans =
+						ExecFindMatchingSubPlans(node->partition_pruning);
+
 		/*
-		 * First time through: pull the first tuple from each subplan, and set
-		 * up the heap.
+		 * First time through: pull the first tuple from each valid subplan,
+		 * and set up the heap.
 		 */
-		for (i = 0; i < node->ms_nplans; i++)
+		i = -1;
+		while ((i = bms_next_member(node->ms_valid_subplans, i)) >= 0)
 		{
 			node->ms_slots[i] = ExecProcNode(node->mergeplans[i]);
 			if (!TupIsNull(node->ms_slots[i]))
@@ -295,6 +374,19 @@ ExecReScanMergeAppend(MergeAppendState *node)
 {
 	int			i;
 
+	/*
+	 * If any of the parameters being used for partition pruning have changed,
+	 * then we'd better unset the valid subplans so that they are reselected
+	 * for the new parameter values.
+	 */
+	if (node->partition_pruning &&
+		bms_overlap(node->ps.chgParam,
+					node->partition_pruning->execparams))
+	{
+		bms_free(node->ms_valid_subplans);
+		node->ms_valid_subplans = NULL;
+	}
+
 	for (i = 0; i < node->ms_nplans; i++)
 	{
 		PlanState  *subnode = node->mergeplans[i];
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index ee4c70aef8..739a023965 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -276,6 +276,7 @@ _copyMergeAppend(const MergeAppend *from)
 	COPY_POINTER_FIELD(sortOperators, from->numCols * sizeof(Oid));
 	COPY_POINTER_FIELD(collations, from->numCols * sizeof(Oid));
 	COPY_POINTER_FIELD(nullsFirst, from->numCols * sizeof(bool));
+	COPY_NODE_FIELD(part_prune_infos);
 
 	return newnode;
 }
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index e22ad4d4dd..e31b6a9c33 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -450,6 +450,8 @@ _outMergeAppend(StringInfo str, const MergeAppend *node)
 	appendStringInfoString(str, " :nullsFirst");
 	for (i = 0; i < node->numCols; i++)
 		appendStringInfo(str, " %s", booltostr(node->nullsFirst[i]));
+
+	WRITE_NODE_FIELD(part_prune_infos);
 }
 
 static void
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index 2e22da6c4f..5bf3d28c51 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -1697,6 +1697,7 @@ _readMergeAppend(void)
 	READ_OID_ARRAY(sortOperators, local_node->numCols);
 	READ_OID_ARRAY(collations, local_node->numCols);
 	READ_BOOL_ARRAY(nullsFirst, local_node->numCols);
+	READ_NODE_FIELD(part_prune_infos);
 
 	READ_DONE();
 }
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 76fe80fbb7..d6c94846d3 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -1144,6 +1144,8 @@ create_merge_append_plan(PlannerInfo *root, MergeAppendPath *best_path)
 	List	   *pathkeys = best_path->path.pathkeys;
 	List	   *subplans = NIL;
 	ListCell   *subpaths;
+	RelOptInfo *rel = best_path->path.parent;
+	List	   *partpruneinfos = NIL;
 
 	/*
 	 * We don't have the actual creation of the MergeAppend node split out
@@ -1229,8 +1231,40 @@ create_merge_append_plan(PlannerInfo *root, MergeAppendPath *best_path)
 		subplans = lappend(subplans, subplan);
 	}
 
+	if (rel->reloptkind == RELOPT_BASEREL &&
+		best_path->partitioned_rels != NIL)
+	{
+		List	   *prunequal;
+
+		prunequal = extract_actual_clauses(rel->baserestrictinfo, false);
+
+		if (best_path->path.param_info)
+		{
+
+			List	   *prmquals = best_path->path.param_info->ppi_clauses;
+
+			prmquals = extract_actual_clauses(prmquals, false);
+			prmquals = (List *) replace_nestloop_params(root,
+														(Node *) prmquals);
+
+			prunequal = list_concat(prunequal, prmquals);
+		}
+
+		/*
+		 * If any quals exist, then these may be useful to allow us to perform
+		 * further partition pruning during execution.  We'll generate a
+		 * PartitionPruneInfo for each partitioned rel to store these quals
+		 * and allow translation of partition indexes into subpath indexes.
+		 */
+		if (prunequal != NIL)
+			partpruneinfos = make_partition_pruneinfo(root,
+											best_path->partitioned_rels, NIL,
+											best_path->subpaths, prunequal);
+	}
+
 	node->partitioned_rels = best_path->partitioned_rels;
 	node->mergeplans = subplans;
+	node->part_prune_infos = partpruneinfos;
 
 	return (Plan *) node;
 }
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 5890209fee..9851f35f77 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1155,6 +1155,12 @@ struct AppendState
  *		slots			current output tuple of each subplan
  *		heap			heap of active tuples
  *		initialized		true if we have fetched first tuple from each subplan
+ *		noopscan		true if partition pruning proved that none of the
+ *						mergeplans can contain a record to satisfy this query.
+ *		partition_pruning	details required to allow partitions to be
+ *							eliminated from the scan, or NULL if not possible.
+ *		ms_valid_subplans	for runtime pruning, valid mergeplans indexes to
+ *							scan.
  * ----------------
  */
 typedef struct MergeAppendState
@@ -1167,6 +1173,9 @@ typedef struct MergeAppendState
 	TupleTableSlot **ms_slots;	/* array of length ms_nplans */
 	struct binaryheap *ms_heap; /* binary heap of slot indices */
 	bool		ms_initialized; /* are subplans started? */
+	bool		ms_noopscan;	/* true if no subplans need scanned */
+	struct PartitionPruning *partition_pruning;
+	Bitmapset   *ms_valid_subplans;
 } MergeAppendState;
 
 /* ----------------
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index c3e5c2c79f..0b5189aa7d 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -280,6 +280,10 @@ typedef struct MergeAppend
 	Oid		   *sortOperators;	/* OIDs of operators to sort them by */
 	Oid		   *collations;		/* OIDs of collations */
 	bool	   *nullsFirst;		/* NULLS FIRST/LAST directions */
+	/*
+	 * Mapping details for run-time subplan pruning, one per partitioned_rels
+	 */
+	List	   *part_prune_infos;
 } MergeAppend;
 
 /* ----------------
diff --git a/src/test/regress/expected/partition_prune.out b/src/test/regress/expected/partition_prune.out
index 0a2517125c..792924fe0b 100644
--- a/src/test/regress/expected/partition_prune.out
+++ b/src/test/regress/expected/partition_prune.out
@@ -2651,3 +2651,148 @@ select * from boolp where a = (select value from boolvalues where not value);
 (9 rows)
 
 drop table boolp;
+--
+-- Test run-time pruning of MergeAppend subnodes
+--
+set enable_seqscan = off;
+set enable_sort = off;
+create table ma_test (a int) partition by range (a);
+create table ma_test_p1 partition of ma_test for values from (0) to (10);
+create table ma_test_p2 partition of ma_test for values from (10) to (20);
+create table ma_test_p3 partition of ma_test for values from (20) to (30);
+insert into ma_test select x from generate_series(0,29) t(x);
+create index on ma_test (a);
+analyze ma_test;
+prepare mt_q1 (int) as select * from ma_test where a >= $1 and a % 10 = 5 order by a;
+-- Execute query 5 times to allow choose_custom_plan
+-- to start considering a generic plan.
+execute mt_q1(0);
+ a  
+----
+  5
+ 15
+ 25
+(3 rows)
+
+execute mt_q1(0);
+ a  
+----
+  5
+ 15
+ 25
+(3 rows)
+
+execute mt_q1(0);
+ a  
+----
+  5
+ 15
+ 25
+(3 rows)
+
+execute mt_q1(0);
+ a  
+----
+  5
+ 15
+ 25
+(3 rows)
+
+execute mt_q1(0);
+ a  
+----
+  5
+ 15
+ 25
+(3 rows)
+
+explain (analyze, costs off, summary off, timing off) execute mt_q1(15);
+                                     QUERY PLAN                                     
+------------------------------------------------------------------------------------
+ Merge Append (actual rows=2 loops=1)
+   Sort Key: ma_test_p2.a
+   Subplans Pruned: 1
+   ->  Index Only Scan using ma_test_p2_a_idx on ma_test_p2 (actual rows=1 loops=1)
+         Index Cond: (a >= $1)
+         Filter: ((a % 10) = 5)
+         Rows Removed by Filter: 4
+         Heap Fetches: 5
+   ->  Index Only Scan using ma_test_p3_a_idx on ma_test_p3 (actual rows=1 loops=1)
+         Index Cond: (a >= $1)
+         Filter: ((a % 10) = 5)
+         Rows Removed by Filter: 9
+         Heap Fetches: 10
+(13 rows)
+
+execute mt_q1(15);
+ a  
+----
+ 15
+ 25
+(2 rows)
+
+explain (analyze, costs off, summary off, timing off) execute mt_q1(25);
+                                     QUERY PLAN                                     
+------------------------------------------------------------------------------------
+ Merge Append (actual rows=1 loops=1)
+   Sort Key: ma_test_p3.a
+   Subplans Pruned: 2
+   ->  Index Only Scan using ma_test_p3_a_idx on ma_test_p3 (actual rows=1 loops=1)
+         Index Cond: (a >= $1)
+         Filter: ((a % 10) = 5)
+         Rows Removed by Filter: 4
+         Heap Fetches: 5
+(8 rows)
+
+execute mt_q1(25);
+ a  
+----
+ 25
+(1 row)
+
+-- Ensure MergeAppend behaves correctly when no subplans match
+explain (analyze, costs off, summary off, timing off) execute mt_q1(35);
+                                 QUERY PLAN                                  
+-----------------------------------------------------------------------------
+ Merge Append (actual rows=0 loops=1)
+   Sort Key: ma_test_p1.a
+   Subplans Pruned: 2
+   ->  Index Only Scan using ma_test_p1_a_idx on ma_test_p1 (never executed)
+         Index Cond: (a >= $1)
+         Filter: ((a % 10) = 5)
+         Heap Fetches: 0
+(7 rows)
+
+execute mt_q1(35);
+ a 
+---
+(0 rows)
+
+deallocate mt_q1;
+-- ensure initplan params properly prune partitions
+explain (analyze, costs off, summary off, timing off) select * from ma_test where a >= (select min(a) from ma_test_p2) order by a;
+                                                   QUERY PLAN                                                    
+-----------------------------------------------------------------------------------------------------------------
+ Merge Append (actual rows=20 loops=1)
+   Sort Key: ma_test_p1.a
+   InitPlan 2 (returns $1)
+     ->  Result (actual rows=1 loops=1)
+           InitPlan 1 (returns $0)
+             ->  Limit (actual rows=1 loops=1)
+                   ->  Index Only Scan using ma_test_p2_a_idx on ma_test_p2 ma_test_p2_1 (actual rows=1 loops=1)
+                         Index Cond: (a IS NOT NULL)
+                         Heap Fetches: 1
+   ->  Index Only Scan using ma_test_p1_a_idx on ma_test_p1 (never executed)
+         Index Cond: (a >= $1)
+         Heap Fetches: 0
+   ->  Index Only Scan using ma_test_p2_a_idx on ma_test_p2 (actual rows=10 loops=1)
+         Index Cond: (a >= $1)
+         Heap Fetches: 10
+   ->  Index Only Scan using ma_test_p3_a_idx on ma_test_p3 (actual rows=10 loops=1)
+         Index Cond: (a >= $1)
+         Heap Fetches: 10
+(18 rows)
+
+reset enable_seqscan;
+reset enable_sort;
+drop table ma_test;
diff --git a/src/test/regress/sql/partition_prune.sql b/src/test/regress/sql/partition_prune.sql
index eefbf32e93..6f389bed1f 100644
--- a/src/test/regress/sql/partition_prune.sql
+++ b/src/test/regress/sql/partition_prune.sql
@@ -618,3 +618,44 @@ explain (analyze, costs off, summary off, timing off)
 select * from boolp where a = (select value from boolvalues where not value);
 
 drop table boolp;
+
+--
+-- Test run-time pruning of MergeAppend subnodes
+--
+set enable_seqscan = off;
+set enable_sort = off;
+create table ma_test (a int) partition by range (a);
+create table ma_test_p1 partition of ma_test for values from (0) to (10);
+create table ma_test_p2 partition of ma_test for values from (10) to (20);
+create table ma_test_p3 partition of ma_test for values from (20) to (30);
+insert into ma_test select x from generate_series(0,29) t(x);
+create index on ma_test (a);
+
+analyze ma_test;
+prepare mt_q1 (int) as select * from ma_test where a >= $1 and a % 10 = 5 order by a;
+
+-- Execute query 5 times to allow choose_custom_plan
+-- to start considering a generic plan.
+execute mt_q1(0);
+execute mt_q1(0);
+execute mt_q1(0);
+execute mt_q1(0);
+execute mt_q1(0);
+
+explain (analyze, costs off, summary off, timing off) execute mt_q1(15);
+execute mt_q1(15);
+explain (analyze, costs off, summary off, timing off) execute mt_q1(25);
+execute mt_q1(25);
+-- Ensure MergeAppend behaves correctly when no subplans match
+explain (analyze, costs off, summary off, timing off) execute mt_q1(35);
+execute mt_q1(35);
+
+deallocate mt_q1;
+
+-- ensure initplan params properly prune partitions
+explain (analyze, costs off, summary off, timing off) select * from ma_test where a >= (select min(a) from ma_test_p2) order by a;
+
+reset enable_seqscan;
+reset enable_sort;
+
+drop table ma_test;
-- 
2.16.2.windows.1