database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-02 09:02:37 +03:00
Code Activity

Advance multiple array keys rightmost-first instead of leftmost-first

Browse Source 
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.
This commit is contained in:
Tom Lane
2008-03-18 03:54:52 +00:00
parent a2f1827dfd
commit 8e850b9159
1 changed files with 8 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
src/backend/executor/nodeIndexscan.c
View File

@ -8,7 +8,7 @@
* *
* *
* IDENTIFICATION * 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; bool found = false;
int j; 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; ScanKey scan_key = arrayKeys[j].scan_key;
int next_elem = arrayKeys[j].next_elem; int next_elem = arrayKeys[j].next_elem;