diff options
| author | Tom Lane <tgl@sss.pgh.pa.us> | 2022-07-12 16:30:36 -0400 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2022-07-12 16:30:36 -0400 |
| commit | af72b0889441e5ece199f782511d84d72fa6b88c (patch) | |
| tree | c3a419f5a45ddd69ef4eb9efbabdd0f9fc59d859 /src/backend/statistics/mvdistinct.c | |
| parent | 5e7608e81ebb2a9e2a72ab771eba3c620c0b42a6 (diff) | |
Invent qsort_interruptible().
Justin Pryzby reported that some scenarios could cause gathering
of extended statistics to spend many seconds in an un-cancelable
qsort() operation. To fix, invent qsort_interruptible(), which is
just like qsort_arg() except that it will also do CHECK_FOR_INTERRUPTS
every so often. This bloats the backend by a couple of kB, which
seems like a good investment. (We considered just enabling
CHECK_FOR_INTERRUPTS in the existing qsort and qsort_arg functions,
but there are some callers for which that'd demonstrably be unsafe.
Opt-in seems like a better way.)
For now, just apply qsort_interruptible() in statistics collection.
There's probably more places where it could be useful, but we can
always change other call sites as we find problems.
Back-patch to v14. Before that we didn't have extended stats on
expressions, so that the problem was less severe. Also, this patch
depends on the sort_template infrastructure introduced in v14.
Tom Lane and Justin Pryzby
Discussion: https://postgr.es/m/20220509000108.GQ28830@telsasoft.com
Diffstat (limited to 'src/backend/statistics/mvdistinct.c')
| -rw-r--r-- | src/backend/statistics/mvdistinct.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/src/backend/statistics/mvdistinct.c b/src/backend/statistics/mvdistinct.c index 4481312d61d..4b4ecec9361 100644 --- a/src/backend/statistics/mvdistinct.c +++ b/src/backend/statistics/mvdistinct.c @@ -488,8 +488,8 @@ ndistinct_for_combination(double totalrows, StatsBuildData *data, } /* We can sort the array now ... */ - qsort_arg((void *) items, numrows, sizeof(SortItem), - multi_sort_compare, mss); + qsort_interruptible((void *) items, numrows, sizeof(SortItem), + multi_sort_compare, mss); /* ... and count the number of distinct combinations */ |