Horton

Re: select_parallel test failure: gather sometimes losing tuples (maybe during rescans)?

Thomas Munro <thomas.munro@enterprisedb.com>

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From: Thomas Munro <thomas.munro@enterprisedb.com>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: Andres Freund <andres@anarazel.de>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2018-03-04T03:37:01Z
Lists: pgsql-hackers 
On Sun, Mar 4, 2018 at 4:17 PM, Tomas Vondra
<tomas.vondra@2ndquadrant.com> wrote:
> On 03/04/2018 04:11 AM, Thomas Munro wrote:
>> On Sun, Mar 4, 2018 at 4:07 PM, Tomas Vondra
>> <tomas.vondra@2ndquadrant.com> wrote:
>>> ! ERROR:  lost connection to parallel worker
>>
>> That sounds like the new defences from 2badb5afb89cd569500ef7c3b23c7a9d11718f2f.
>
> Yeah. But I wonder why the worker fails at all, or how to find that.

Could it be that a concurrency bug causes tuples to be lost on the
tuple queue, and also sometimes causes X (terminate) messages to be
lost from the error queue, so that the worker appears to go away
unexpectedly?

-- 
Thomas Munro
http://www.enterprisedb.com

Commits

  1. shm_mq: Fix detach race condition.

  2. shm_mq: Have the receiver set the sender's less frequently.

  3. shm_mq: Reduce spinlock usage.

  4. Report an ERROR if a parallel worker fails to start properly.