Re: locks in CREATE TRIGGER, ADD FK

From: Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl>
To: Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)au>
Cc: Russell Smith <mr-russ(at)pws(dot)com(dot)au>, Neil Conway <neilc(at)samurai(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: locks in CREATE TRIGGER, ADD FK
Date: 2005-03-23 02:49:41
Message-ID: 20050323024941.GA7702@dcc.uchile.cl
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On Wed, Mar 23, 2005 at 10:42:01AM +0800, Christopher Kings-Lynne wrote:
> >>If you want to be my friend forever, then fix CLUSTER so that it uses
> >>sharerowexclusive as well :D
> >
> >I don't think it's as easy as that, because you have to move tuples
> >around in the cluster operation. Same sort of issue as vacuum full I
> >would suggest.
>
> Cluster doesn't move rows...
>
> I didn't say it was easy. It would involve changing how cluster works.
> It would keep the old table around while building the new, then grab
> an exclusive lock to swap the two.

Huh, cluster already does that.

I don't remember what the rationale was for locking the table, leaving
even simple SELECTs out. (In fact, IIRC the decision wasn't made by me,
and it wasn't discussed at all.)

--
Alvaro Herrera (<alvherre[(at)]dcc(dot)uchile(dot)cl>)
"I would rather have GNU than GNOT." (ccchips, lwn.net/Articles/37595/)

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