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: 2017-05-02T15:05:38Z
Lists: pgsql-bugs, pgsql-hackers 
On 4/27/17 01:52, Andres Freund wrote:
> In contrast to <v10, the actual change of the tuple is *not* happening
> with the page lock held.  But now we do log XLOG_SEQ_LOG, then unlock
> the buffer, and then do a CatalogTupleUpdate().  How is that correct?

The change to the sequence data and the change to the catalog are two
separate operations.  There is no need AFAICT for the latter to be done
while the former is locked or vice versa.

-- 
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