Re: nested xacts and phantom Xids

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl>
Cc: Patches <pgsql-patches(at)postgresql(dot)org>
Subject: Re: nested xacts and phantom Xids
Date: 2004-06-22 04:42:30
Message-ID: 10941.1087879350@sss.pgh.pa.us
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Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl> writes:
> On Mon, Jun 21, 2004 at 10:28:59PM -0400, Tom Lane wrote:
>> Also, rather than labeling each entry individually, it might be better
>> to keep a separate list for each level of transaction. Then instead of
>> relabeling, you'd just concat the subtrans list to its parent's. Seems
>> like this should be faster and less storage.

> Right, but it makes harder to detect when a duplicate relcache entry is
> going to be inserted. Judging from the commentary in the file this is
> an issue.

It's only a minor efficiency hack; don't get too tense about avoiding dups.
(We don't bother to check for dup catcache-inval entries at all...)
The only thing I'd suggest you need to preserve is the business about
invalidating catcache before relcache; again that's just an efficiency
hack, but it seems simple enough to be worth doing.

regards, tom lane

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