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Re: This script will crash the connection

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Jan Wieck <janwieck(at)Yahoo(dot)com>
Cc: Steve Howe <howe(at)carcass(dot)dhs(dot)org>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: This script will crash the connection
Date: 2001-01-26 18:30:16
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
Jan Wieck <janwieck(at)Yahoo(dot)com> writes:
> Tom Lane wrote:
>> The problem here is that the query rewriter tries to hang the query's
>> qualification (WHERE clause) onto the rule's action query, so that
>> the action query won't be done unless the query finds at least one
>> row to update.
>> NOTIFY commands, being utility statements, don't have qualifications.
>> In 7.0 and before, the qual clause just vanished into the ether, and
>> so in this example the NOTIFY would execute whether the UPDATE updated
>> any rows or not.  In 7.1 there is physically noplace to hang the qual
>> (no jointree) and thus a crash.

>     Would be something for a STATEMENT trigger. We don't have 'em
>     yet and I'm not sure  what  kind  of  information  they  will
>     receive  if we finally implement them. But the number of rows
>     affected by the statement is a good candidate.

That's no help for a 7.1 solution however.  We can't start inventing
a new feature at this stage.

What I am inclined to do is have the rewriter reject conditional rules
that contain NOTIFY.  That seems like the minimal restriction that will
prevent a crash or incorrect behavior.  Comments?

			regards, tom lane

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