8000 Hashed LEFT JOIN would miss outer tuples with no inner match if the join · danielcode/postgres@f4d5c52 · GitHub
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Hashed LEFT JOIN would miss outer tuples with no inner match if the join
was large enough to be batched and the tuples fell into a batch where there were no inner tuples at all. Thanks to Xiaoyu Wang for finding a test case that exposed this long-standing bug.
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src/backend/executor/nodeHashjoin.c

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@@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/executor/nodeHashjoin.c,v 1.38 2001/03/22 06:16:13 momjian Exp $
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* $Header: /cvsroot/pgsql/src/backend/executor/nodeHashjoin.c,v 1.38.2.1 2004/09/17 18:29:54 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
@@ -575,12 +575,14 @@ ExecHashJoinNewBatch(HashJoinState *hjstate)
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}
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/*
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* We can skip over any batches that are empty on either side. Release
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* associated temp files right away.
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* Normally we can skip over any batches that are empty on either side
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* --- but for JOIN_LEFT, can only skip when left side is empty.
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* Release associated temp files right away.
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*/
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while (newbatch <= nbatch &&
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(innerBatchSize[newbatch - 1] == 0L ||
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outerBatchSize[newbatch - 1] == 0L))
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(outerBatchSize[newbatch - 1] == 0L ||
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(innerBatchSize[newbatch - 1] == 0L &&
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hjstate->js.jointype != JOIN_LEFT)))
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{
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BufFileClose(hashtable->innerBatchFile[newbatch - 1]);
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hashtable->innerBatchFile[newbatch - 1] = NULL;

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