[GLUTEN-12172][CH] Fix group limit first array result offset#12173
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RowNumGroupArraySorted writes aggregate results into a newly created ColumnArray. For the first output row the array offsets vector can be empty, but insertResultInto read result_array_offsets.back() before appending the first offset. That is undefined behavior and can crash when aggregate top-k writes its first result. Treat an empty offsets vector as having previous offset 0 before appending the next cumulative offset. Add a ClickHouse backend regression test that forces row_number top-k through the aggregate group limit path and validates the first array result row against vanilla Spark.
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What changes are proposed in this pull request?
RowNumGroupArraySorted writes aggregate results into a newly created ColumnArray. For the first output row the array offsets vector can be empty, but insertResultInto read result_array_offsets.back() before appending the first offset. That is undefined behavior and can crash when aggregate top-k writes its first result.
Treat an empty offsets vector as having previous offset 0 before appending the next cumulative offset. Add a ClickHouse backend regression test that forces row_number top-k through the aggregate group limit path and validates the first array result row against vanilla Spark.
closed #12172
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Was this patch authored or co-authored using generative AI tooling?
co-authored using generative AI tooling