Re: Evaluation of if conditions

Daniel,

AFAIK there is no short-circuiting of evaluations in postgres and I don't think you can depend on the order they appear in to determine the order in which they are checked, although more knowledgable people may have better info than I ... so the rewritten form is the way to go.

Greg Williamson
DBA
GlobeXplorer LLC

-----Original Message-----
From: pgsql-sql-owner(at)postgresql(dot)org on behalf of Daniel CAUNE
Sent: Wed 9/6/2006 3:32 PM
To: pgsql-sql(at)postgresql(dot)org
Cc:
Subject: [SQL] Evaluation of if conditions

Hi,

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
statement
END IF;

Should be rewritten as (for example):

IF (TG_OP = 'INSERT') THEN
statement
ELSIF (OLD.bar = ...) THEN
statement
END IF;

Regards,

--
Daniel

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