| From: | "Jim C(dot) Nasby" <jim(at)nasby(dot)net> |
|---|---|
| To: | pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: SELECT blocking on ALTER TABLE ADD FOREIGN KEY |
| Date: | 2003-06-16 06:17:38 |
| Message-ID: | 20030616061738.GE40542@flake.decibel.org |
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| Lists: | pgsql-hackers |
On Thu, Jun 12, 2003 at 06:23:12PM -0400, Tom Lane wrote:
> "Jim C. Nasby" <jim(at)nasby(dot)net> writes:
> > Is there any ALTER that would require blocking selects?
>
> DROP INDEX, for certain.
Sure, but that's usually trivially fast.
> > Even stuff like
> > drop and rename should be protected by versioning, no?
>
> No. System-catalog changes are always READ COMMITTED mode.
Yeah, so the catalog changes shouldn't be visible to anyone until after
the ALTER is complete, right? Even if a transaction is set to read
uncommitted, I assume it will always read only committed data from the
catalogs...
--
Jim C. Nasby (aka Decibel!) jim(at)nasby(dot)net
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