Horton

Re: Concurrent ALTER SEQUENCE RESTART Regression

Peter Eisentraut <peter.eisentraut@2ndquadrant.com>

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From: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
To: Andres Freund <andres@anarazel.de>
Cc: Michael Paquier <michael.paquier@gmail.com>, Jason Petersen <jason@citusdata.com>, PostgreSQL mailing lists <pgsql-bugs@postgresql.org>
Date: 2017-04-27T02:07:03Z
Lists: pgsql-bugs, pgsql-hackers 
On 4/26/17 21:12, Andres Freund wrote:
> I think it's unacceptable to regress with an error message here.  I've
> seen sequence DDL being used while concurrent DML was onging in a number
> of production use cases, and just starting to error out instead of
> properly blocking doesn't seem acceptable to me.

It's not clear to me what the use case is here that we are optimizing
for.  The best solution would depend on that.  Running concurrent ALTER
SEQUENCE in a tight loop is probably not it. ;-)

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

  1. Make ALTER SEQUENCE, including RESTART, fully transactional.

  2. Modify sequence catalog tuple before invoking post alter hook.

  3. Use weaker locks when updating pg_subscription_rel

  4. Add pg_sequence system catalog

  5. Modify sequence state storage to eliminate dangling-pointer problem