HIVE-29503: Prevent Join cardinality overestimation of joins with NDV(0) columns#6356
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konstantinb wants to merge 7 commits intoapache:masterfrom
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HIVE-29503: Prevent Join cardinality overestimation of joins with NDV(0) columns#6356konstantinb wants to merge 7 commits intoapache:masterfrom
konstantinb wants to merge 7 commits intoapache:masterfrom
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…ng the join product row count with an NDV of 0
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Mar 23, 2026
| input vertices: | ||
| 1 Map 2 | ||
| Statistics: Num rows: 4 Data size: 1184 Basic stats: COMPLETE Column stats: COMPLETE | ||
| Statistics: Num rows: 2 Data size: 325 Basic stats: COMPLETE Column stats: NONE |
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at the moment. NDV of datetime/timestamp columns is not being assigned to colstats even if available. Changing that will make this estimate better; however, doing impacts over 100 .out files so perhaps doing so belongs to a separate story?
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these were introduced by #6361 |
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What changes were proposed in this pull request?
HIVE-29503: Use the fallback of half the number of rows when estimating the join product row count with an NDV of 0
Why are the changes needed?
Does this PR introduce any user-facing change?
How was this patch tested?