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For bulk write operations (eg COPY IN), use a ring buffer of 16MB instead

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of the 256KB limit originally enforced by a patch committed 2008-11-06.
Per recent test results, the smaller size resulted in an undesirable decrease
in bulk data loading speed, due to COPY processing frequently getting blocked
for WAL flushing.  This area might need more tweaking later, but this setting
seems to be good enough for 8.4.
This commit is contained in:
Tom Lane 2009-06-22 20:04:28 +00:00
parent 3f1e529e78
commit 6382448cf9
2 changed files with 10 additions and 7 deletions
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9
src/backend/storage/buffer/README
View File

@ -1,4 +1,4 @@
$PostgreSQL: pgsql/src/backend/storage/buffer/README,v 1.16 2009/02/18 15:58:41 heikki Exp $
$PostgreSQL: pgsql/src/backend/storage/buffer/README,v 1.17 2009/06/22 20:04:28 tgl Exp $
Notes About Shared Buffer Access Rules
======================================
@ -237,7 +237,12 @@ buffer, resulting in excessive WAL flushing. Allowing VACUUM to update
Bulk writes work similarly to VACUUM. Currently this applies only to
COPY IN and CREATE TABLE AS SELECT. (Might it be interesting to make
seqscan UPDATE and DELETE use the bulkwrite strategy?)
seqscan UPDATE and DELETE use the bulkwrite strategy?) For bulk writes
we use a ring size of 16MB (but not more than 1/8th of shared_buffers).
Smaller sizes have been shown to result in the COPY blocking too often
for WAL flushes. While it's okay for a background vacuum to be slowed by
doing its own WAL flushing, we'd prefer that COPY not be subject to that,
so we let it use up a bit more of the buffer arena.
Background Writer's Processing

8
src/backend/storage/buffer/freelist.c
View File

@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/buffer/freelist.c,v 1.66 2009/01/01 17:23:47 momjian Exp $
* $PostgreSQL: pgsql/src/backend/storage/buffer/freelist.c,v 1.67 2009/06/22 20:04:28 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -368,9 +368,7 @@ GetAccessStrategy(BufferAccessStrategyType btype)
int ring_size;
/*
* Select ring size to use. See buffer/README for rationales. (Currently
* all cases are the same size, but keep this code structure for
* flexibility.)
* Select ring size to use. See buffer/README for rationales.
*
* Note: if you change the ring size for BAS_BULKREAD, see also
* SYNC_SCAN_REPORT_INTERVAL in access/heap/syncscan.c.
@ -385,7 +383,7 @@ GetAccessStrategy(BufferAccessStrategyType btype)
ring_size = 256 * 1024 / BLCKSZ;
break;
case BAS_BULKWRITE:
ring_size = 256 * 1024 / BLCKSZ;
ring_size = 16 * 1024 * 1024 / BLCKSZ;
break;
case BAS_VACUUM:
ring_size = 256 * 1024 / BLCKSZ;