fix: support PostgreSQL GROUPS window frames

[jianjindream]

Fixes #2431

What

Add support for PostgreSQL GROUPS window frames and all four window frame exclusions.

How

• Add WindowElement.Type.GROUPS.
• Treat GROUPS as a reserved structural keyword.
• Add WindowElement.Exclusion for:
  • EXCLUDE CURRENT ROW
  • EXCLUDE GROUP
  • EXCLUDE TIES
  • EXCLUDE NO OTHERS
• Keep TIES and OTHERS contextual so they remain usable as unquoted identifiers outside the frame-exclusion grammar.
• Keep deparsing centralized in WindowElement.toString().

Tests

• Assert the parsed analytic expression, non-null window element, frame type, and exclusion type.
• Cover BETWEEN ... AND ..., a single-sided frame, a named WINDOW, and all four frame exclusions.
• Verify ties and others remain usable as identifiers.
• ./gradlew clean check
• mvn clean verify

[Copilot]

Pull request overview

Adds PostgreSQL-compatible support for GROUPS window frames, enabling parsing/deparsing of ... OVER ( ... GROUPS ... ) frame specifications (fixes #2431).

Changes:

• Added GROUPS as a non-reserved keyword so it can still be used as an unquoted identifier outside window-frame contexts.
• Extended WindowElement.Type with GROUPS and updated the window-frame grammar to accept GROUPS alongside ROWS/RANGE.
• Added unit tests covering GROUPS BETWEEN ... AND ..., single-sided UNBOUNDED PRECEDING, and named WINDOW definitions.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/test/java/net/sf/jsqlparser/statement/select/WindowFunctionTest.java	Adds regression/variant tests asserting AST typing and round-trip deparse for GROUPS frames.
src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt	Adds GROUPS token to non-reserved keywords and accepts it in the WindowElement frame-mode grammar.
src/main/java/net/sf/jsqlparser/expression/WindowElement.java	Extends WindowElement.Type enum to include GROUPS for AST representation and deparsing.

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[manticore-projects]

Thank you for working on this.

PostgreSQL's (and SQL:2011's) frame clause has a third component that JSqlParser's WindowElement() doesn't model at all. It bites harder in GROUPS mode and so I do wonder if not adding full support while you are on it.

{ RANGE | ROWS | GROUPS } frame_start [ frame_exclusion ]
{ RANGE | ROWS | GROUPS } BETWEEN frame_start AND frame_end [ frame_exclusion ]

frame_exclusion ::= EXCLUDE CURRENT ROW
                  | EXCLUDE GROUP
                  | EXCLUDE TIES
                  | EXCLUDE NO OTHERS

With your PR this meaningful query still fails:

SELECT id, ts, value,
       SUM(value) OVER (ORDER BY ts
                        GROUPS BETWEEN 1 PRECEDING AND CURRENT ROW
                        EXCLUDE TIES) AS sum_excl_ties
FROM events
ORDER BY ts, id;

Furthermore, promoting a word to a token breaks every production taking a raw <S_IDENTIFIER>: CREATE SCHEMA (~10496), SET PATH (~10538), Oracle KEEP (~9121), interval type (~9092), COLLATE (7912), and the nested ColDataType() lookahead (10873). We either need to declare it a reserved keyword (which was reasonable) or make at least CREATE SCHEMA work with it.

[jianjindream]

Thanks for the detailed review. I’ve updated the PR in 43710af to model all four frame exclusions: EXCLUDE CURRENT ROW, EXCLUDE GROUP, EXCLUDE TIES, and EXCLUDE NO OTHERS.

I also moved GROUPS to the reserved token set instead of broadening productions that only accept raw identifiers. TIES and OTHERS remain contextual identifiers, so they are only recognized specially after EXCLUDE and remain usable as ordinary unquoted identifiers elsewhere.

The tests now cover all four exclusions, the GROUPS ... EXCLUDE TIES query, explicit AST type/non-null assertions, named windows, and identifier compatibility. The updated Gradle and Maven CI checks are green.

[manticore-projects]

Very nice! Thank you much for your contribution!