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Re: Compressing the AFTER TRIGGER queue

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Compressing the AFTER TRIGGER queue
Date: 2011-08-01 17:36:09
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Lists: pgsql-hackers
On Mon, Aug 1, 2011 at 1:31 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com> writes:
>> On 1 August 2011 17:49, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> Ummm ... I only read the data structure comments, not the code, but I
>>> don't see where you store the second CTID for an update event?
>> Ah yes, I forgot to mention that bit. I'm using
>> &(tuple1.t_data->t_ctid) to get the second CTID from the old tuple. Is
>> that safe?
> Hmmmm ... not sure.  It seems a bit scary, but on the other hand we
> should be able to assume that the updating subtransaction hasn't been
> rolled back (else surely we shouldn't be firing the trigger).  So in
> principle it seems like the t_ctid link can't have been replaced.
> This will foreclose any ideas about collapsing t_ctid link chains,
> if anyone had it in mind to do that.

Don't we already do that when pruning HOT chains?

Robert Haas
The Enterprise PostgreSQL Company

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