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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2008-03-18 03:54:52 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2008-03-18 03:54:52 +0000 |
| commit | 8e850b9159b1519dcc20982c39cfc3ff16d3d31b (patch) | |
| tree | 406e8db8c63a4aea6448478923047cc07279cc67 /src/backend/executor/nodeIndexscan.c | |
| parent | a2f1827dfd21a670272d7c7ffe2d4902cfff990e (diff) | |
| download | postgresql-8e850b9159b1519dcc20982c39cfc3ff16d3d31b.tar.gz postgresql-8e850b9159b1519dcc20982c39cfc3ff16d3d31b.zip | |
Advance multiple array keys rightmost-first instead of leftmost-first
during a bitmap index scan. This cannot affect the query results
(since we're just dumping the TIDs into a bitmap) but it might offer
some advantage in locality of access to the index. Per Greg Stark.
Diffstat (limited to 'src/backend/executor/nodeIndexscan.c')
| -rw-r--r-- | src/backend/executor/nodeIndexscan.c | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/src/backend/executor/nodeIndexscan.c b/src/backend/executor/nodeIndexscan.c index 2db4015504e..59f54ee5cb4 100644 --- a/src/backend/executor/nodeIndexscan.c +++ b/src/backend/executor/nodeIndexscan.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/executor/nodeIndexscan.c,v 1.125 2008/01/01 19:45:49 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/executor/nodeIndexscan.c,v 1.126 2008/03/18 03:54:52 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -352,7 +352,13 @@ ExecIndexAdvanceArrayKeys(IndexArrayKeyInfo *arrayKeys, int numArrayKeys) bool found = false; int j; - for (j = 0; j < numArrayKeys; j++) + /* + * Note we advance the rightmost array key most quickly, since it will + * correspond to the lowest-order index column among the available + * qualifications. This is hypothesized to result in better locality + * of access in the index. + */ + for (j = numArrayKeys - 1; j >= 0; j--) { ScanKey scan_key = arrayKeys[j].scan_key; int next_elem = arrayKeys[j].next_elem; |