| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Cédric Villemain <cedric(dot)villemain(dot)debian(at)gmail(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Peter Eisentraut <peter_e(at)gmx(dot)net>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: ALTER TABLE SET STATISTICS requires AccessExclusiveLock |
| Date: | 2010-07-09 17:18:01 |
| Message-ID: | 1278695881.29736.748.camel@ebony |
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| Lists: | pgsql-hackers |
On Fri, 2010-07-09 at 13:04 -0400, Robert Haas wrote:
> Tom asked what happens when two transactions attempt to do concurrent
> actions on the same table. Your response was that we should handle it
> like CREATE INDEX, and handle the update of the pg_class row
> non-transactionally. But of course, if you use a self-conflicting
> lock at the relation level, then the relation locks conflict and you
> never have to worry about how to update the pg_class entry in the face
> of concurrent updates.
>From memory, Tom was also worried about the prospect of people updating
pg_class directly using SQL. That seems a rare, yet valid concern.
I've already agreed with your point that we should use SHARE UPDATE
EXCLUSIVE.
--
Simon Riggs www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Training and Services
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