Be more wary about 32-bit integer overflow in pg_stat_statements. We've heard a couple of reports of people having trouble with multi-gigabyte-sized query-texts files. It occurred to me that on 32-bit platforms, there could be an issue with integer overflow of calculations associated with the total query text size. Address that with several changes:
1. Limit pg_stat_statements.max to INT_MAX / 2 not INT_MAX. The hashtable code will bound it to that anyway unless "long" is 64 bits. We still need overflow guards on its use, but this helps. 2. Add a check to prevent extending the query-texts file to more than MaxAllocHugeSize. If it got that big, qtext_load_file would certainly fail, so there's not much point in allowing it. Without this, we'd need to consider whether extent, query_offset, and related variables shouldn't be off_t not size_t. 3. Adjust the comparisons in need_gc_qtexts() to be done in 64-bit arithmetic on all platforms. It appears possible that under duress those multiplications could overflow 32 bits, yielding a false conclusion that we need to garbage-collect the texts file, which could lead to repeatedly garbage-collecting after every hash table insertion. Per report from Bruno da Silva. I'm not convinced that these issues fully explain his problem; there may be some other bug that's contributing to the query-texts file becoming so large in the first place. But it did get that big, so #2 is a reasonable defense, and #3 could explain the reported performance difficulties. (See also commit 8bbe4cbd9, which addressed some related bugs. The second Discussion: link is the thread that led up to that.) This issue is old, and is primarily a problem for old platforms, so back-patch. Discussion: https://postgr.es/m/cab+nuk93fl1q9elocotvlp07g7rav4vbdrkm0cvqohdvmpa...@mail.gmail.com Discussion: https://postgr.es/m/5601d354.5000...@bluetreble.com Branch ------ REL_10_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/dd414bf4e047e55028db28172e8184fcd2ee1201 Modified Files -------------- contrib/pg_stat_statements/pg_stat_statements.c | 26 +++++++++++++++++++++---- 1 file changed, 22 insertions(+), 4 deletions(-)
