Horton

Re: ALTER TABLE lock strength reduction patch is unsafe

Robert Haas <robertmhaas@gmail.com>

View thread
From: Robert Haas <robertmhaas@gmail.com>
To: Simon Riggs <simon@2ndquadrant.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2011-06-17T19:15:34Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Add bytea_agg, parallel to string_agg.

  2. Fix ALTER TABLE ONLY .. DROP CONSTRAINT.

On Fri, Jun 17, 2011 at 3:08 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
> Not so. The extra locking would only occur on the first lock
> acquisition after DDL operations occur. If that was common then your
> other performance patch would not be an effective optimisation. There
> is no additional locking from what I've proposed in the common code
> path - that's why we have a relcache.

The extra locking would also occur when *initially* building relcache
entries.  In other words, this would increase - likely quite
significantly - the overhead of backend startup.  It's not going to be
sufficient to do this just for pg_class; I think you'll have to do it
for pg_attribute, pg_attrdef, pg_constraint, pg_index, pg_trigger,
pg_rewrite, and maybe a few others I'm not thinking of right now.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company