8000 Allow `row_number` `rank` without `PARTITION BY` when using Top-N pattern · Issue #21991 · risingwavelabs/risingwave · GitHub
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Allow row_number rank without PARTITION BY when using Top-N pattern #21991

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stdrc opened this issue May 26, 2025 · 1 comment
Open

Allow row_number rank without PARTITION BY when using Top-N pattern #21991

stdrc opened this issue May 26, 2025 · 1 comment
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A-topn Area: TopN type/perf Type: Performance.

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stdrc commented May 26, 2025

For top-N queies with something like RANK() OVER (PARTITION BY CAST(1 AS INT) ORDER BY some_column) AS rank, the plan won't be optimal because we don't do 2-phase optimization for GroupTopN, but the function call actually is global TopN (group by a constant). Since the number of input for OverWindow is limited after GroupTopN, we can allow eliminate PARTITION BY in such queries.
@stdrc stdrc added type/perf Type: Performance. A-topn Area: TopN labels May 26, 2025
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stdrc commented May 26, 2025

As a background, we currently don't support general window function calls without PARTITION BY because we believe the performance won't be good and the user should rethink about their query. #11505

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A-topn Area: TopN type/perf Type: Performance.
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