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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2018-10-08 10:41:34 -0400 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2018-10-08 10:41:34 -0400 |
| commit | f9eb7c14b08d2cc5eda62ffaf37a356c05e89b93 (patch) | |
| tree | 9ebff1fa4bbee6b88e8856dcc9016be1969b86c6 /src/backend/executor/execUtils.c | |
| parent | eee01d606eb40f760799320e75d45c84022353d8 (diff) | |
| download | postgresql-f9eb7c14b08d2cc5eda62ffaf37a356c05e89b93.tar.gz postgresql-f9eb7c14b08d2cc5eda62ffaf37a356c05e89b93.zip | |
Avoid O(N^2) cost in ExecFindRowMark().
If there are many ExecRowMark structs, we spent O(N^2) time in
ExecFindRowMark during executor startup. Once upon a time this was
not of great concern, but the addition of native partitioning has
squeezed out enough other costs that this can become the dominant
overhead in some use-cases for tables with many partitions.
To fix, simply replace that List data structure with an array.
This adds a little bit of cost to execCurrentOf(), but not much,
and anyway that code path is neither of large importance nor very
efficient now. If we ever decide it is a bottleneck, constructing a
hash table for lookup-by-tableoid would likely be the thing to do.
Per complaint from Amit Langote, though this is different from
his fix proposal.
Discussion: https://postgr.es/m/468c85d9-540e-66a2-1dde-fec2b741e688@lab.ntt.co.jp
Diffstat (limited to 'src/backend/executor/execUtils.c')
| -rw-r--r-- | src/backend/executor/execUtils.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/src/backend/executor/execUtils.c b/src/backend/executor/execUtils.c index d98e90e7117..71c6b5dc0a8 100644 --- a/src/backend/executor/execUtils.c +++ b/src/backend/executor/execUtils.c @@ -113,6 +113,7 @@ CreateExecutorState(void) estate->es_range_table_array = NULL; estate->es_range_table_size = 0; estate->es_relations = NULL; + estate->es_rowmarks = NULL; estate->es_plannedstmt = NULL; estate->es_junkFilter = NULL; @@ -142,8 +143,6 @@ CreateExecutorState(void) estate->es_tupleTable = NIL; - estate->es_rowMarks = NIL; - estate->es_processed = 0; estate->es_lastoid = InvalidOid; @@ -709,6 +708,12 @@ ExecInitRangeTable(EState *estate, List *rangeTable) */ estate->es_relations = (Relation *) palloc0(estate->es_range_table_size * sizeof(Relation)); + + /* + * es_rowmarks is also parallel to the es_range_table_array, but it's + * allocated only if needed. + */ + estate->es_rowmarks = NULL; } /* |