Message-ID: <44FF5404.2010604@oisinglynn.com>
Date: Wed, 06 Sep 2006 19:04:36 -0400
From: Oisin Glynn <me@oisinglynn.com>
Reply-To: me@oisinglynn.com
User-Agent: Thunderbird 1.5.0.5 (Windows/20060719)
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To: Daniel CAUNE <d.caune@free.fr>
CC: pgsql-sql@postgresql.org
Subject: Re: Evaluation of if conditions
References: <001601c6d204$5d2cd840$0b00a8c0@tedy>
In-Reply-To: <001601c6d204$5d2cd840$0b00a8c0@tedy>
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Daniel CAUNE wrote:
> 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
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 9: In versions below 8.0, the planner will ignore your desire to
>        choose an index scan if your joining column's datatypes do not
>        match
>   
The following is working fine for me on 8.1.x on Windows. I am not sure 
what order it is evaluating the if statement in but it is working correctly.
Oisin


CREATE OR REPLACE FUNCTION zfunc_testor(bool, bool)
  RETURNS "varchar" AS
$BODY$DECLARE


v_1 boolean;
v_2 boolean;

BEGIN

v_1 :=$1;
v_2 := $2;

if (v_1 = TRUE) OR (v_2 = TRUE) then
   return 'At least 1 true';
else
    return 'neither true';
end if;

END;$BODY$
  LANGUAGE 'plpgsql' VOLATILE;
ALTER FUNCTION zfunc_testor(bool, bool) OWNER TO postgres;