RE: pg_stat_statements: duplicated external query texts with MSY2

>Julien Rouhaud <rjuju123@gmail.com> writes:
>> On Mon, Jun 8, 2020 at 11:28 PM legrand legrand
>> <legrand_legrand@hotmail.com> wrote:
>>> pgbench -i postgres
>>> pgbench -c20 -t5 postgres
>>> generates the attached pgss_query_texts.stat,
>>> where "BEGIN" and "UPDATE pgbench_accounts SET abalance = abalance + $1 WHERE aid = $2"
>>> appears 20 times ...

>> Is the duplication only in the query text file?  Looking at the code
>> the query text part is stored holding a shared lwlock, so it seems
>> like an expected behavior (less overhead but might store duplicated
>> query text)

> I agree, this looks like operating-as-designed: different processes can
> store the same query text and only later discover that they were creating
> duplicate hash table entries.  It's a bit surprising that the duplication
> would be reproducible, but it just depends on timing.  Maybe this is
> telling us something about how scheduling works under MSYS2.
>
>                        regards, tom lane