From: Tom Lane <tgl@sss.pgh.pa.us>
To: Daniel CAUNE <d.caune@free.fr>
Cc: pgsql-sql@postgresql.org
Subject: Re: Evaluation of if conditions
Date: Thu, 07 Sep 2006 00:10:18 -0400
Message-ID: <28985.1157602218@sss.pgh.pa.us> (raw)
In-Reply-To: <001601c6d204$5d2cd840$0b00a8c0@tedy>
References: <001601c6d204$5d2cd840$0b00a8c0@tedy>
Daniel CAUNE <d.caune@free.fr> writes:
> How does the IF statement evaluate conditions? Does it evaluate conditions
> following their declaration order from left to right? In case of
> or-conditions, does the IF statement stop evaluating conditions whenever a
> first or-condition is true?
> The following snippet seems to be invalid, which let me think that PL/PGSQL
> evaluates all the conditions:
> IF (TG_OP = 'INSERT') OR
> (OLD.bar = ...) THEN
It's not that all the conditions get evaluated by an OR, it's that
plpgsql needs to send all the parameter values that the IF-expression
needs down to the core SQL engine. So it fails on "OLD.bar" not being
defined, long before the expression evaluator gets to think about
whether TG_OP = 'INSERT' or not.
So, yeah, you want to rewrite it as two separate IF-tests.
regards, tom lane
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, d.caune@free.fr
Subject: Re: Evaluation of if conditions
In-Reply-To: <28985.1157602218@sss.pgh.pa.us>
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