Re: WIP: extensible enums

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Andrew Dunstan <andrew(at)dunslane(dot)net>, Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: WIP: extensible enums
Date: 2010-10-23 23:33:32
Message-ID: 39B6E838-4028-41A3-8C7C-90FCA3D80F79@gmail.com
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On Oct 23, 2010, at 7:12 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
>> Latest patch attached.
>
> I've been working through this patch. It occurs to me that there's a
> fairly serious problem with the current implementation of insertion of
> new values within the bounds of the current sort ordering. Namely, that
> it does that by reassigning the enumsortorder values of pre-existing
> rows. That creates a race condition:

It strikes me that this is merely one facet of our failure to do proper locking on DDL objects other than relations, and that this would be as good a time as any to start fixing it. ISTM that ALTER TYPE should grab a self-excluding lock just as ALTER TABLE already does.

...Robert

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