Horton

Re: TopoSort() fix

Alvaro Herrera <alvherre@2ndquadrant.com>

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From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>, Michael Paquier <michael@paquier.xyz>, Andres Freund <andres@anarazel.de>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2019-07-30T03:21:57Z
Lists: pgsql-hackers 
On 2019-Jul-29, Tom Lane wrote:

> FYI, I just got done inventing a way to reach that code, and I have
> to suspect that it's impossible to do so in production, because under
> ordinary circumstances no parallel worker will take any exclusive lock
> that isn't already held by its leader.

Hmm, okay, so this wasn't a bug that would have bit anyone in practice,
yeah?  That's reassuring.

Thanks,

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

  1. Add an isolation test to exercise parallel-worker deadlock resolution.

  2. Mark advisory-lock functions as parallel restricted, not parallel unsafe.

  3. Fix busted logic for parallel lock grouping in TopoSort().