[princejain756]

Resolves #2785.

PostgreSQL accepts an optional ALL or DISTINCT modifier directly after GROUP BY:

SELECT 1 GROUP BY DISTINCT GROUPING SETS ((1), (1));
SELECT 1 GROUP BY ALL GROUPING SETS ((1), (2));
SELECT a FROM t GROUP BY DISTINCT a;

The DISTINCT form removes duplicate grouping sets before processing (PostgreSQL docs). JSQLParser rejected it at the DISTINCT token.

This adds a semantic-lookahead-gated ALL|DISTINCT slot in GroupByColumnReferences, active only under the POSTGRESQL dialect, plus all/distinct flags on GroupByElement so both toString and the deparser round-trip the modifier. Other dialects and existing GROUP BY forms are unchanged.

10,735 tests, 0 failures, 25 skipped.

[manticore-projects]

Am I right to assume that this overlaps with #2830 but is broader?
If so, please resolve conflicts and I would merge.

[princejain756]

Correct - #2830 handles GROUPING SETS under GROUP BY DISTINCT, while this adds ALL and DISTINCT before any grouping element, so it covers that case plus plain columns and rollups. Conflicts resolved, rebased on master.

[manticore-projects]

Thank you much!