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fix: don't double count column join keys in SortMergeJoinExec buffered batch reservation - #27346
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Kristofferjoha wants to merge 2 commits into
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vinycalves
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Nov 12, 2026
vinycalves
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Two logic questions; no code suggestions.
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Does the new test cover a computed join key and the spill/read-back path, where the key array is actually unshared? When a batch spills, does the reservation still avoid double-counting buffers shared with the key arrays?
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Thanks, added a test which covers a computed key and the spill/read-back path. On spill the batch is dropped, so only the key arrays stay in memory and they’re counted once.
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Which issue does this PR close?
Rationale for this change
BufferedBatch::try_newreservesbatch.get_array_memory_size()plus the size of each evaluated join key array. For a column key, the key array is the batch's own column, so that column is counted twice. Joins on wide string keys reserve about twice what they hold, and spill or fail under a memory limit earlier than they should.What changes are included in this PR?
BufferedBatch::try_newonly charges key buffers the batch doesn't already hold, usingRecordBatchMemoryCounter.With the repro from the issue both queries now report 19.5 MB (was 38.8 MB and 19.7 MB).
What is the testing strategy for this PR?
Added
column_join_key_not_double_counted, which checks thatpeak_mem_usedis the same for an int key and a string key over the same data.Updated the expected
peak_mem_usedinexplain_analyze.slt(432 B -> 288 B) and the size formula in three existing spill tests.The re-evaluation on restore is not covered by a test.
Are there any user-facing changes?
No.