Re: Bugs in CREATE/DROP INDEX CONCURRENTLY

On 2012-11-28 18:41:39 -0500, Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > On 2012-11-28 17:42:18 -0500, Tom Lane wrote:
> >> I agree it's a judgment call, though. Anybody want to argue for the
> >> other position?
>
> > Hm. Seems odd to include indexes that are being dropped concurrently at
> > that moment. But then, we can't really detect that situation and as you
> > say its consistent with pg_dump...
>
> [ thinks about that for a bit... ] We could have that, for about the same
> cost as the currently proposed patch: instead of defining the added flag
> column as "index is live", define it as "drop in progress", and set it
> immediately at the start of the DROP CONCURRENTLY sequence. Then the
> "dead" condition that RelationGetIndexList must check for is "drop in
> progress and not indisvalid and not indisready".

You're right.

> However, this is more complicated and harder to understand. So unless
> somebody is really excited about being able to tell the difference
> between create-in-progress and drop-in-progress, I'd rather leave the
> patch as-is.

The only real argument for doing this that I can see is a potential
REINDEX CONCURRENTLY.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
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