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Use streaming read for VACUUM cleanup of GIN

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This commit replace the synchronous ReadBufferExtended() loop done in
ginvacuumcleanup() with the streaming read equivalent, to improve I/O
efficiency during GIN index vacuum cleanup operations.

With dm_delay to emulate some latency and debug_io_direct=data to force
synchronous writes and force the read path to be exercised, the author
has noticed a 5x improvement in runtime, with a substantial reduction in
IO stats numbers.  I have reproduced similar numbers while running
similar tests, with improvements becoming better with more tuples and
more pages manipulated.

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 2026-03-12 11:48:31 +09:00
parent 383eb21ebf
commit 6c228755ad
1 changed files with 26 additions and 2 deletions
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28
src/backend/access/gin/ginvacuum.c
View file

@ -22,6 +22,7 @@
#include "storage/indexfsm.h"
#include "storage/lmgr.h"
#include "storage/predicate.h"
#include "storage/read_stream.h"
#include "utils/memutils.h"
struct GinVacuumState
@ -693,6 +694,8 @@ ginvacuumcleanup(IndexVacuumInfo *info, IndexBulkDeleteResult *stats)
BlockNumber totFreePages;
GinState ginstate;
GinStatsData idxStat;
BlockRangeReadStreamPrivate p;
ReadStream *stream;
/*
* In an autovacuum analyze, we want to clean up pending insertions.
@ -743,6 +746,24 @@ ginvacuumcleanup(IndexVacuumInfo *info, IndexBulkDeleteResult *stats)
totFreePages = 0;
/* Scan all blocks starting from the root using streaming reads */
p.current_blocknum = GIN_ROOT_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_MAINTENANCE |
READ_STREAM_FULL |
READ_STREAM_USE_BATCHING,
info->strategy,
index,
MAIN_FORKNUM,
block_range_read_stream_cb,
&p,
0);
for (blkno = GIN_ROOT_BLKNO; blkno < npages; blkno++)
{
Buffer buffer;
@ -750,8 +771,8 @@ ginvacuumcleanup(IndexVacuumInfo *info, IndexBulkDeleteResult *stats)
vacuum_delay_point(false);
buffer = ReadBufferExtended(index, MAIN_FORKNUM, blkno,
RBM_NORMAL, info->strategy);
buffer = read_stream_next_buffer(stream, NULL);
LockBuffer(buffer, GIN_SHARE);
page = BufferGetPage(buffer);
@ -776,6 +797,9 @@ ginvacuumcleanup(IndexVacuumInfo *info, IndexBulkDeleteResult *stats)
UnlockReleaseBuffer(buffer);
}
Assert(read_stream_next_buffer(stream, NULL) == InvalidBuffer);
read_stream_end(stream);
/* Update the metapage with accurate page and entry counts */
idxStat.nTotalPages = npages;
ginUpdateStats(info->index, &idxStat, false);