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Re: BUG #5989: Assertion failure on UPDATE of big value

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "Heikki Linnakangas" <heikki(dot)linnakangas(at)enterprisedb(dot)com>, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Marko Tiikkaja" <marko(dot)tiikkaja(at)2ndquadrant(dot)com>, <pgsql-bugs(at)postgresql(dot)org>
Subject: Re: BUG #5989: Assertion failure on UPDATE of big value
Date: 2011-04-20 15:26:57
Message-ID: 4DAEB4F1020000250003CA92@gw.wicourts.gov (view raw or flat)
Thread:
Lists: pgsql-bugs
Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> On 20.04.2011 17:26, Tom Lane wrote:
 
>> Why is predicate.c getting called at all when
>> transaction_isolation is not SERIALIZABLE?  (Although the same
>> crash happens when it is ...)
> 
> Because another serializable transaction that reads/updates the
> tuple later needs to find the predicate lock acquired by the
> first transaction, even if the transaction in the middle isn't
> serializable.
 
For an example of the issue, see this post:
 
http://archives.postgresql.org/pgsql-hackers/2011-02/msg00325.php
 
While all transactions there are serializable, the issue exists even
if the transaction which updates the tuple with the predicate lock
isn't serializable.
 
-Kevin

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