Thread

Re: Row pattern recognition

Henson Choi <assam258@gmail.com> — 2026-05-09T07:43:18Z

Hi Tatsuo,


Eleven incremental patches on top of v47.  Patches 0001-0010
are the same set I posted on 2026-05-07, with cosmetic touches
only.  Patch 0011 is new and tightens the consistency of how
this code base cites the SQL standard.

So far I have been pushing ahead narrowly on the feature
implementation itself.  I am aware I still have much to learn
about the PostgreSQL project's culture and conventions, and
your continued guidance would be very much appreciated.


Patch summary:


  - 0001 Add DEFINE non-volatile baseline to rpr_integration B9
      Adds a STABLE/IMMUTABLE baseline ahead of the volatile
      case so the rejection in 0002 is visible against a working
      reference.


  - 0002 Unify RPR DEFINE walkers and reject volatile callees
      [A].  Collapses the four DEFINE walkers (parser / planner
      / executor) into one phase-tagged traversal and, on that
      base, rejects volatile / NextValueExpr at parse-analysis.
      STABLE / IMMUTABLE accepted.  The offset runtime-constant
      check is folded in; B9 flips to error-case and its XXX is
      dropped.


  - 0003 Cover RPR empty-match path with EXPLAIN tests; fix
         stale XXX comments
      [B].  Adds rpr_explain coverage that surfaces "NFA: N
      matched (len 0/0/0.0)" so the NFA-found-but-empty-frame
      path is regression-visible; replaces stale rpr_nfa XXXs.


  - 0004 Reclassify DEFINE qualifier check and reword
         diagnostic to "expression"
      [D].  Tri-classifies (pattern var / range var / fall-
      through) so unknown qualifiers fall through to the
      standard "column does not exist" diagnostic.  Reworded to
      "expression" since the quoted token may include
      indirection on composite types (e.g. (A.items).amount).


  - 0005 Sync stale comments on DEFINE/PATTERN handling
      validateRPRPatternVarCount() rejects DEFINE names not in
      PATTERN, but comments / SELECT doc described it as
      "collection" / "filtered during planning".  Wording
      aligned; XXX note's "column references" bumped to
      "expressions" to match 0004.  Comment + doc only.


  - 0006 Add trailing commas to RPR enum definitions
      Per Jian.  RPRNavKind, RPRNavOffsetKind, RPRPatternNodeType.


  - 0007 Remove optional outer parentheses from ereport() calls
         in RPR files
      Per Jian + your gram.y patch.  19 sites in parse_rpr.c /
      optimizer/plan/rpr.c plus the gram.y sites.


  - 0008 Add high-water mark tracking to NFA visited bitmap
         reset
      [C].  Resets only the touched span (O(span_words) instead
      of O(numElements/64)), at the cost of two int16 comparisons
      per visit.  Semantics unchanged; happy to drop if you
      prefer the simpler bulk reset.


  - 0009 Document DEFINE subquery rejection as intentional
         over-rejection
      Comment-only.  Records that SQL/RPR permits a non-RPR,
      non-pattern-var-correlated subquery in DEFINE (see 0011
      for the normalized citation), and that our blanket
      rejection is deliberate over-rejection.  The case
      distinction (walk subquery Query for nested RPR; match
      ColumnRef qualifiers against ancestor p_rpr_pattern_vars)
      is doable with existing infrastructure and left as future
      work, not blocked on any other feature.


  - 0010 Remove duplicate #include in nodeWindowAgg.c
      "common/int.h" was included twice and the first occurrence
      was misplaced between catalog/* headers.  Drops the
      misplaced first; the second sits at the correct
      alphabetical position.


  - 0011 Normalize SQL/RPR standard references across code,
         comments, and tests
      Doc/comment/test-header hygiene.  Standardizes citations
      to ISO/IEC 19075-5 (SQL Technical Report Part 5, "Row
      pattern recognition in SQL"); earlier comments mixed bare
      "19075-5", "9075-2", "SQL standard", and "SQL:2016 STR06"
      forms.  Where Chapter 4 (FROM / R010) and Chapter 6
      (WINDOW / R020) describe parallel material, cites the
      Chapter 6 subclause first since this implementation
      targets R020.  Pins "STR06" to its source (Subclause
      7.2.8) in the rpr_nfa / rpr_explain commentary; replaces
      ad-hoc section / arrow glyphs with ASCII.  Adds a short
      normative-reference paragraph to executor/README.rpr so
      future patches inherit the policy.  Comments / docs /
      test headers only.


Still deferred:
  - B7 Recursive CTE XXX: pending community input on the
    ISO/IEC 19075-5 6.17.5 / 4.18.5 interpretation.


Best regards,
Henson