diff options
author | Tom Lane <tgl@sss.pgh.pa.us> | 2012-05-22 19:42:12 -0400 |
---|---|---|
committer | Tom Lane <tgl@sss.pgh.pa.us> | 2012-05-22 19:42:12 -0400 |
commit | 276bea211f08a3b0d6d5753b654322c8efb781d1 (patch) | |
tree | 5963c42ce69afbadd0827fbbdcecb07c5512063e /src | |
parent | ae7c8b290f525504978c01d77366a753505d10d5 (diff) | |
download | postgresql-276bea211f08a3b0d6d5753b654322c8efb781d1.tar.gz postgresql-276bea211f08a3b0d6d5753b654322c8efb781d1.zip |
Ensure that seqscans check for interrupts at least once per page.
If a seqscan encounters many consecutive pages containing only dead tuples,
it can remain in the loop in heapgettup for a long time, and there was no
CHECK_FOR_INTERRUPTS anywhere in that loop. This meant there were
real-world situations where a query would be effectively uncancelable for
long stretches. Add a check placed to occur once per page, which should be
enough to provide reasonable response time without adding any measurable
overhead.
Report and patch by Merlin Moncure (though I tweaked it a bit).
Back-patch to all supported branches.
Diffstat (limited to 'src')
-rw-r--r-- | src/backend/access/heap/heapam.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c index cc8b45fd489..197067d4a1d 100644 --- a/src/backend/access/heap/heapam.c +++ b/src/backend/access/heap/heapam.c @@ -219,6 +219,13 @@ heapgetpage(HeapScanDesc scan, BlockNumber page) scan->rs_cbuf = InvalidBuffer; } + /* + * Be sure to check for interrupts at least once per page. Checks at + * higher code levels won't be able to stop a seqscan that encounters + * many pages' worth of consecutive dead tuples. + */ + CHECK_FOR_INTERRUPTS(); + /* read page using selected strategy */ scan->rs_cbuf = ReadBufferExtended(scan->rs_rd, MAIN_FORKNUM, page, RBM_NORMAL, scan->rs_strategy); |