rdelaage
/
postgresql
mirror of https://git.postgresql.org/git/postgresql.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Report syncscan position at end of scan. 

The comment in heapgettup_advance_block() says that it reports the
scan position before checking for end of scan, but that didn't match
the code. The code was refactored in commit 7ae0ab0ad9, which
inadvertently changed the order of the check and reporting. Change it
back.

This caused a few regression test failures with a small shared_buffers
setting like 10 MB. The 'portals' and 'cluster' tests perform seqscans
that are large enough that sync seqscans kick in. When the sync scan
position is not updated at end of scan, the next seq scan doesn't
start at the beginning of the table, and the test queries are
sensitive to that.

Reviewed-by: Melanie Plageman, David Rowley
Discussion: https://www.postgresql.org/message-id/6f991389-ae22-d844-a9d8-9aceb7c01a9a@iki.fi
Backpatch-through: 16
This commit is contained in:
Heikki Linnakangas 2023-08-31 13:02:15 +03:00
parent d7ceb41b9b
commit e8d74ad625
1 changed files with 11 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
src/backend/access/heap/heapam.c
View File

@ -647,17 +647,6 @@ heapgettup_advance_block(HeapScanDesc scan, BlockNumber block, ScanDirection dir
if (block >= scan->rs_nblocks)
block = 0;
/* we're done if we're back at where we started */
if (block == scan->rs_startblock)
return InvalidBlockNumber;
/* check if the limit imposed by heap_setscanlimits() is met */
if (scan->rs_numblocks != InvalidBlockNumber)
{
if (--scan->rs_numblocks == 0)
return InvalidBlockNumber;
}
/*
* Report our new scan position for synchronization purposes. We
* don't do that when moving backwards, however. That would just
@ -673,6 +662,17 @@ heapgettup_advance_block(HeapScanDesc scan, BlockNumber block, ScanDirection dir
if (scan->rs_base.rs_flags & SO_ALLOW_SYNC)
ss_report_location(scan->rs_base.rs_rd, block);
/* we're done if we're back at where we started */
if (block == scan->rs_startblock)
return InvalidBlockNumber;
/* check if the limit imposed by heap_setscanlimits() is met */
if (scan->rs_numblocks != InvalidBlockNumber)
{
if (--scan->rs_numblocks == 0)
return InvalidBlockNumber;
}
return block;
}
else