hcq/postgresql
1
0
Fork 0
mirror of https://git.postgresql.org/git/postgresql.git synced 2026-03-19 18:46:57 +08:00
Code Issues Packages Projects Releases Wiki Activity

bloom: Optimize bitmap scan path with streaming read

Browse Source 
This commit replaces the per-page buffer read look in blgetbitmap() with
a reading stream, to improve scan efficiency, particularly useful for
large bloom indexes.  Some benchmarking with a large number of rows has
shown a very nice improvement in terms of runtime and IO read reduction
with test cases up to 10M rows for a bloom index scan.

For the io_uring method, The author has reported a 3x in runtime with
io_uring while I was at close to a 7x.  For the worker method with 3
workers, the author has reported better numbers than myself in runtime,
with the reduction in IO stats being appealing for all the cases
measured.

Author: Xuneng Zhou <xunengzhou@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Nazir Bilal Yavuz <byavuz81@gmail.com>
Discussion: https://postgr.es/m/CABPTF7VrqfbcDXqGrdLQ2xaQ=K0RzExNuw6U_GGqzSJu32wfdQ@mail.gmail.com
This commit is contained in:
Michael Paquier
2026-03-11 07:36:10 +09:00
parent 4c7362c553
commit 4c910f3bbe
1 changed files with 25 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

29
contrib/bloom/blscan.c
View File

@ -18,6 +18,7 @@
#include "miscadmin.h"
#include "pgstat.h"
#include "storage/bufmgr.h"
#include "storage/read_stream.h"
/*
* Begin scan of bloom index.
@ -76,11 +77,13 @@ int64
blgetbitmap(IndexScanDesc scan, TIDBitmap *tbm)
{
int64 ntids = 0;
BlockNumber blkno = BLOOM_HEAD_BLKNO,
BlockNumber blkno,
npages;
int i;
BufferAccessStrategy bas;
BloomScanOpaque so = (BloomScanOpaque) scan->opaque;
BlockRangeReadStreamPrivate p;
ReadStream *stream;
if (so->sign == NULL)
{
@ -120,14 +123,29 @@ blgetbitmap(IndexScanDesc scan, TIDBitmap *tbm)
if (scan->instrument)
scan->instrument->nsearches++;
/* Scan all blocks except the metapage using streaming reads */
p.current_blocknum = BLOOM_HEAD_BLKNO;
p.last_exclusive = npages;
/*
* It is safe to use batchmode as block_range_read_stream_cb takes no
* locks.
*/
stream = read_stream_begin_relation(READ_STREAM_FULL |
READ_STREAM_USE_BATCHING,
bas,
scan->indexRelation,
MAIN_FORKNUM,
block_range_read_stream_cb,
&p,
0);
for (blkno = BLOOM_HEAD_BLKNO; blkno < npages; blkno++)
{
Buffer buffer;
Page page;
buffer = ReadBufferExtended(scan->indexRelation, MAIN_FORKNUM,
blkno, RBM_NORMAL, bas);
buffer = read_stream_next_buffer(stream, NULL);
LockBuffer(buffer, BUFFER_LOCK_SHARE);
page = BufferGetPage(buffer);
@ -163,6 +181,9 @@ blgetbitmap(IndexScanDesc scan, TIDBitmap *tbm)
UnlockReleaseBuffer(buffer);
CHECK_FOR_INTERRUPTS();
}
Assert(read_stream_next_buffer(stream, NULL) == InvalidBuffer);
read_stream_end(stream);
FreeAccessStrategy(bas);
return ntids;