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Fix off-by-one error in read IO tracing

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AsyncReadBuffer()'s no-IO needed path passed
TRACE_POSTGRESQL_BUFFER_READ_DONE the wrong block number because it had
already incremented operation->nblocks_done. Fix by folding the
nblocks_done offset into the blocknum local variable at initialization.

Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/u73un3xeljr4fiidzwi4ikcr6vm7oqugn4fo5vqpstjio6anl2%40hph6fvdiiria
Backpatch-through: 18
This commit is contained in:
Andres Freund 2026-03-26 10:07:59 -04:00
parent 906a046972
commit cf66978d79
1 changed files with 3 additions and 3 deletions
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6
src/backend/storage/buffer/bufmgr.c
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@ -1875,10 +1875,10 @@ AsyncReadBuffers(ReadBuffersOperation *operation, int *nblocks_progress)
{
Buffer *buffers = &operation->buffers[0];
int flags = operation->flags;
BlockNumber blocknum = operation->blocknum;
ForkNumber forknum = operation->forknum;
char persistence = operation->persistence;
int16 nblocks_done = operation->nblocks_done;
BlockNumber blocknum = operation->blocknum + nblocks_done;
Buffer *io_buffers = &operation->buffers[nblocks_done];
int io_buffers_len = 0;
PgAioHandle *ioh;
@ -1990,7 +1990,7 @@ AsyncReadBuffers(ReadBuffersOperation *operation, int *nblocks_progress)
* must have started out as a miss in PinBufferForBlock(). The other
* backend will track this as a 'read'.
*/
TRACE_POSTGRESQL_BUFFER_READ_DONE(forknum, blocknum + operation->nblocks_done,
TRACE_POSTGRESQL_BUFFER_READ_DONE(forknum, blocknum,
operation->smgr->smgr_rlocator.locator.spcOid,
operation->smgr->smgr_rlocator.locator.dbOid,
operation->smgr->smgr_rlocator.locator.relNumber,
@ -2062,7 +2062,7 @@ AsyncReadBuffers(ReadBuffersOperation *operation, int *nblocks_progress)
*/
io_start = pgstat_prepare_io_time(track_io_timing);
smgrstartreadv(ioh, operation->smgr, forknum,
blocknum + nblocks_done,
blocknum,
io_pages, io_buffers_len);
pgstat_count_io_op_time(io_object, io_context, IOOP_READ,
io_start, 1, io_buffers_len * BLCKSZ);