clintropolis opened a new pull request #9662: fix issue with group by limit pushdown for extractionFn, expressions, joins, etc URL: https://github.com/apache/druid/pull/9662 ### Description This PR fixes a bug with group by limit pushdown which causes incorrect query results when grouping on string columns ... TBD. #### simple example that illustrates the bug given rows ``` dim1, dim2 ---------- 'a', 'aa' 'a', 'ab' 'a', 'ba ``` and the following query ``` SELECT dim1, substring(dim2, 1, 1), count(*) FROM exampleRows GROUP BY 1,2 LIMIT 2 ``` prior to the changes in this PR the results would be ``` [['a', 'a', 2]] ``` rather than the expected: ``` [['a', 'a', 2],['a', 'b', 1]] ``` <hr> This PR has: - [ ] been self-reviewed. - [ ] added Javadocs for most classes and all non-trivial methods. Linked related entities via Javadoc links. - [x] added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader. - [x] added unit tests or modified existing tests to cover new code paths. - [ ] added integration tests. - [x] been tested in a test Druid cluster.
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