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Commit8e850b9

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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 offersome advantage in locality of access to the index. Per Greg Stark.
1 parenta2f1827 commit8e850b9

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‎src/backend/executor/nodeIndexscan.c

Lines changed: 8 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/executor/nodeIndexscan.c,v 1.125 2008/01/01 19:45:49 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/executor/nodeIndexscan.c,v 1.126 2008/03/18 03:54:52 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
@@ -352,7 +352,13 @@ ExecIndexAdvanceArrayKeys(IndexArrayKeyInfo *arrayKeys, int numArrayKeys)
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boolfound= false;
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intj;
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for (j=0;j<numArrayKeys;j++)
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/*
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* Note we advance the rightmost array key most quickly, since it will
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* correspond to the lowest-order index column among the available
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* qualifications. This is hypothesized to result in better locality
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* of access in the index.
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*/
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for (j=numArrayKeys-1;j >=0;j--)
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{
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ScanKeyscan_key=arrayKeys[j].scan_key;
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intnext_elem=arrayKeys[j].next_elem;

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