Subject: Re: BUG #16329: Valgrind detects an invalid read when building a gist
 index with buffering
From: Alexander Lakhin <exclusion@gmail.com>
To: pgsql-bugs@lists.postgresql.org
References: <16329-7a6aa9b6fa1118a1@postgresql.org>
 <ca1f896b-e5d1-53a7-5bc3-9451ab9aca22@gmail.com>
 <e91e45fd-a614-bb87-e9fc-c556c2b95fe5@gmail.com>
Message-ID: <3dda6945-c147-5afc-7720-38ec6848dafa@gmail.com>
Date: Sat, 2 May 2020 07:45:00 +0300
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06.04.2020 09:00, Alexander Lakhin wrote:
> 30.03.2020 00:00, PG Bug reporting form wrote:
>>> Running the following query under valgrind:
>>> create table gist_point_tbl(id int4, p point);
>>> insert into gist_point_tbl (id, p)
>>> select g, point(g*10+1, g*10+1) from generate_series(1, 30000) g;
>>> create index gist_pointidx2 on gist_point_tbl using gist(p) with (buffering
>>> = on, fillfactor=50);
>>>
>>> leads to a memory access error:
>>> ==00:00:00:08.755 18585== Invalid read of size 2
>>> ==00:00:00:08.756 18585==    at 0x1F94CA: gistBuildCallback
>>> (gistbuild.c:495)
> Please look at the patch that modifies the gist regression test to make
> the issue visible and fixes it by avoiding access to the memory context
> that can be reset in gistProcessEmptyingQueue().
Could you please let me know if the fix is incorrect (or not elaborated
enough to be included in the upcoming releases) or this issue is false
positive?

Best regards,
Alexander