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Arrange for large sequential scans to synchronize with each other, so that

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when multiple backends are scanning the same relation concurrently, each page
is (ideally) read only once.

Jeff Davis, with review by Heikki and Tom.
This commit is contained in:
Tom Lane
2007-06-08 18:23:53 +00:00
parent 6d6d14b6d5
commit a04a423599
10 changed files with 485 additions and 31 deletions
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5
src/backend/storage/buffer/freelist.c
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@@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/buffer/freelist.c,v 1.59 2007/05/30 20:11:59 tgl Exp $
* $PostgreSQL: pgsql/src/backend/storage/buffer/freelist.c,v 1.60 2007/06/08 18:23:52 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -340,6 +340,9 @@ GetAccessStrategy(BufferAccessStrategyType btype)
* Select ring size to use. See buffer/README for rationales.
* (Currently all cases are the same size, but keep this code
* structure for flexibility.)
*
* Note: if you change the ring size for BAS_BULKREAD, see also
* SYNC_SCAN_REPORT_INTERVAL in access/heap/syncscan.c.
*/
switch (btype)
{