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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
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expected | ||
sql | ||
.gitignore | ||
Makefile | ||
pg_stat_statements--1.0--1.1.sql | ||
pg_stat_statements--1.1--1.2.sql | ||
pg_stat_statements--1.2--1.3.sql | ||
pg_stat_statements--1.3--1.4.sql | ||
pg_stat_statements--1.4--1.5.sql | ||
pg_stat_statements--1.4.sql | ||
pg_stat_statements--1.5--1.6.sql | ||
pg_stat_statements--unpackaged--1.0.sql | ||
pg_stat_statements.c | ||
pg_stat_statements.conf | ||
pg_stat_statements.control |