From: Jerry Sievers <gsievers19@comcast.net>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Jerry Sievers <gsievers19@comcast.net>,
  Tomas Vondra <tomas.vondra@2ndquadrant.com>,
  pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: SegFault on 9.6.14
References: <87ims2amh6.fsf@jsievers.enova.com>
	<20190716001529.uvpfngvxtlu5h2fr@development>
	<87blxuakv4.fsf@jsievers.enova.com>
	<20190716003449.fjegtxinhrqubysu@development>
	<87ftn6ojwf.fsf@jsievers.enova.com>
	<20190716082204.iecyfh6mhu6khdhz@development>
	<87blxta8c7.fsf@jsievers.enova.com>
	<CA+hUKGJA8pSGbAsSTLqbvQoLQ63JS4P9ZjdNQ-y+qVbEyjzAdw@mail.gmail.com>
	<8736j5a6no.fsf@jsievers.enova.com>
	<CA+hUKG+HvBn8nhwuLOWy+jDHOLZX4BxAeBEHcSJzhHvudkmv9w@mail.gmail.com>
	<87wogh8qzw.fsf@jsievers.enova.com>
	<CA+hUKG+hrjeSQQEarZv2ewACjRQshnCAtYo9tu0afd=fBzuVnw@mail.gmail.com>
	<87lfwx8q1f.fsf@jsievers.enova.com>
	<CA+hUKG+A4TWxt8g5K5fOunUVQ1jtd3EWco=GoR=funG1UfaeBQ@mail.gmail.com>
Date: Tue, 16 Jul 2019 19:57:50 -0500
In-Reply-To: 
 <CA+hUKG+A4TWxt8g5K5fOunUVQ1jtd3EWco=GoR=funG1UfaeBQ@mail.gmail.com>
	(Thomas Munro's message of "Wed, 17 Jul 2019 12:44:49 +1200")
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Thomas Munro <thomas.munro@gmail.com> writes:

> On Wed, Jul 17, 2019 at 12:26 PM Jerry Sievers <gsievers19@comcast.net> wrote:
>
>> Is this the right sequencing?
>>
>> 1. Start client and get backend pid
>> 2. GDB;  handle SIGUSR1, break, cont
>> 3. Run query
>> 4. bt
>
> Perfect, thanks.  I think I just spotted something:

Dig that!  Great big thanks to you and Tomas, et al for jumping on this.

Please let know if there's anything else I can submit that would be
helpful.


>
>> #11 0x000055666e0359df in ExecShutdownNode (node=node@entry=0x55667033a6c8)
>>     at /build/postgresql-9.6-5O8OLM/postgresql-9.6-9.6.14/build/../src/backend/executor/execProcnode.c:830
>> #12 0x000055666e04d0ff in ExecLimit (node=node@entry=0x55667033a428)
>>     at /build/postgresql-9.6-5O8OLM/postgresql-9.6-9.6.14/build/../src/backend/executor/nodeLimit.c:139
>
> https://github.com/postgres/postgres/blob/REL9_6_STABLE/src/backend/executor/nodeLimit.c#L139
>
> Limit thinks it's OK to "shut down" the subtree, but if you shut down a
> Gather node you can't rescan it later because it destroys its shared
> memory.  Oops.  Not sure what to do about that yet.
>
>
> --
> Thomas Munro
> https://enterprisedb.com
>
>
>

-- 
Jerry Sievers
Postgres DBA/Development Consulting
e: postgres.consulting@comcast.net