Re: locks in CREATE TRIGGER, ADD FK

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Neil Conway <neilc(at)samurai(dot)com>
Cc: Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)au>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: locks in CREATE TRIGGER, ADD FK
Date: 2005-03-23 04:53:58
Message-ID: 1824.1111553638@sss.pgh.pa.us
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Neil Conway <neilc(at)samurai(dot)com> writes:
> - if we make these changes, we will need some way to delete a
> no-longer-visible relfilenode.

This is presuming that we abandon the notion that system catalog
access use SnapshotNow. Which opens the question of what they should
use instead ... to which "transaction snapshot" isn't the answer,
because we have to be able to do system catalog accesses before
we've set the snapshot. (Else forget issuing LOCK TABLE before
the snapshot is set.)

I really think that you haven't the faintest idea of the size of
the can of worms you are opening here :-(

regards, tom lane

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