diff options
| author | Tom Lane <tgl@sss.pgh.pa.us> | 2012-05-22 19:42:28 -0400 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2012-05-22 19:42:28 -0400 |
| commit | c994b9211fd0cf7a5b680ae115330117604b9f7c (patch) | |
| tree | a067e2fa987d01ab84c5c274bea9881b81e0f623 /src | |
| parent | 57615562504a3a10784d10a5205ed4bab41dba6e (diff) | |
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 10644c7d8f1..0dc6611d8dc 100644 --- a/src/backend/access/heap/heapam.c +++ b/src/backend/access/heap/heapam.c @@ -206,6 +206,13 @@ 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 = ReadBufferWithStrategy(scan->rs_rd, page, |