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From: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Date: Tue, 30 Jan 2024 11:52:43 +0530
Message-ID: 
 <CAExHW5uskiHd7A34XbA+0PbW3_modiLGUt-oiP5zBumS-eUb8g@mail.gmail.com>
Subject: Re: tablecmds.c/MergeAttributes() cleanup
To: Alexander Lakhin <exclusion@gmail.com>
Cc: Peter Eisentraut <peter@eisentraut.org>,
 pgsql-hackers <pgsql-hackers@postgresql.org>,
	Alvaro Herrera <alvherre@alvh.no-ip.org>
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Hi Alexander,

On Sun, Jan 28, 2024 at 1:30=E2=80=AFPM Alexander Lakhin <exclusion@gmail.c=
om> wrote:
>
> Hello Peter,
>
> 26.01.2024 16:42, Peter Eisentraut wrote:
> >
> > I have committed all this.  These are great improvements.
> >
>
> Please look at the segmentation fault triggered by the following query si=
nce
> 4d969b2f8:
> CREATE TABLE t1(a text COMPRESSION pglz);
> CREATE TABLE t2(a text);
> CREATE TABLE t3() INHERITS(t1, t2);
> NOTICE:  merging multiple inherited definitions of column "a"
> server closed the connection unexpectedly
>          This probably means the server terminated abnormally
>          before or while processing the request.
>
> Core was generated by `postgres: law regression [local] CREATE TABLE     =
                            '.
> Program terminated with signal SIGSEGV, Segmentation fault.
>
> (gdb) bt
> #0  __strcmp_avx2 () at ../sysdeps/x86_64/multiarch/strcmp-avx2.S:116
> #1  0x00005606fbcc9d52 in MergeAttributes (columns=3D0x0, supers=3Dsupers=
@entry=3D0x5606fe293d30, relpersistence=3D112 'p',
> is_partition=3Dfalse, supconstr=3Dsupconstr@entry=3D0x7fff4046d410, supno=
tnulls=3Dsupnotnulls@entry=3D0x7fff4046d418)
>      at tablecmds.c:2811
> #2  0x00005606fbccd764 in DefineRelation (stmt=3Dstmt@entry=3D0x5606fe26a=
130, relkind=3Drelkind@entry=3D114 'r', ownerId=3D10,
> ownerId@entry=3D0, typaddress=3Dtypaddress@entry=3D0x0,
>      queryString=3DqueryString@entry=3D0x5606fe2695c0 "CREATE TABLE t3() =
INHERITS(t1, t2);") at tablecmds.c:885

This bug existed even before the refactoring.Happens because strcmp()
is called on NULL input (t2's compression is NULL). I already have a
fix for this and will be posting it in [1].

[1] https://www.postgresql.org/message-id/flat/24656cec-d6ef-4d15-8b5b-e8df=
c9c833a7%40eisentraut.org

--=20
Best Wishes,
Ashutosh Bapat