Newbie question about escaping in a function

On Tue, 2004-10-26 at 11:57 -0500, Naeem Bari wrote:

I have a simple function defined thusly:

CREATE OR REPLACE FUNCTION datemath(timestamp with time zone, int4,
varchar)

RETURNS timestamp AS

'

DECLARE

tdat timestamp;

rdat timestamp;

BEGIN

IF ($1 IS NULL) THEN

TDAT := NOW();

ELSE

TDAT := $1;

END IF;

It's neater to use the COALESCE() function, which is designed expressly
for this.

select tdat + interval ''$2 $3'' into rdat;

In PL/pgSQL that should be "select into rdat ..."; but that won't work
in any case because you can't use passed parameters inside a string like
that.

return rdat;

END;

'

LANGUAGE 'plpgsql' VOLATILE;

The problem is the interval part. How do I tell the bugger to use the
second and third params as input to interval? I have tried different
ways of escaping, from \’$2 $3\’ to ‘’$2 $3’’ and everything else in
between, it just doesn’t like it.

You have to construct a command string and use EXECUTE:

CREATE OR REPLACE FUNCTION datemath(timestamp with time zone, int4, varchar)
RETURNS timestamp AS
'DECLARE
tdat TIMESTAMP;
result RECORD;
cmd TEXT;
BEGIN
tdat := COALESCE($1, NOW());
cmd := ''SELECT '' || quote_literal(tdat) ||
''::TIMESTAMP + INTERVAL '' ||
quote_literal($2 || '' '' || $3) || '' AS x'';
FOR result IN EXECUTE cmd LOOP
return result.x;
END LOOP;
END;
'
LANGUAGE 'plpgsql' VOLATILE;

--
Oliver Elphick olly@lfix.co.uk
Isle of Wight http://www.lfix.co.uk/oliver
GPG: 1024D/A54310EA 92C8 39E7 280E 3631 3F0E 1EC0 5664 7A2F A543 10EA
========================================
"Whosoever therefore shall be ashamed of me and of my
words in this adulterous and sinful generation; of him
also shall the Son of man be ashamed, when he cometh
in the glory of his Father with the holy angels."
Mark 8:38

Thanks! Now I get it...

naeem

-----Original Message-----
From: Oliver Elphick [mailto:olly@lfix.co.uk]
Sent: Tuesday, October 26, 2004 3:05 PM
To: Naeem Bari
Cc: pgsql-general@postgresql.org
Subject: Re: [GENERAL] Newbie question about escaping in a function

On Tue, 2004-10-26 at 11:57 -0500, Naeem Bari wrote:

I have a simple function defined thusly:

CREATE OR REPLACE FUNCTION datemath(timestamp with time zone, int4,
varchar)

RETURNS timestamp AS

'

DECLARE

tdat timestamp;

rdat timestamp;

BEGIN

IF ($1 IS NULL) THEN

TDAT := NOW();

ELSE

TDAT := $1;

END IF;

It's neater to use the COALESCE() function, which is designed expressly
for this.

select tdat + interval ''$2 $3'' into rdat;

In PL/pgSQL that should be "select into rdat ..."; but that won't work
in any case because you can't use passed parameters inside a string like
that.

return rdat;

END;

'

LANGUAGE 'plpgsql' VOLATILE;

The problem is the interval part. How do I tell the bugger to use the
second and third params as input to interval? I have tried different
ways of escaping, from \'$2 $3\' to ''$2 $3'' and everything else in
between, it just doesn't like it.

You have to construct a command string and use EXECUTE:

CREATE OR REPLACE FUNCTION datemath(timestamp with time zone, int4,
varchar)
RETURNS timestamp AS
'DECLARE
tdat TIMESTAMP;
result RECORD;
cmd TEXT;
BEGIN
tdat := COALESCE($1, NOW());
cmd := ''SELECT '' || quote_literal(tdat) ||
''::TIMESTAMP + INTERVAL '' ||
quote_literal($2 || '' '' || $3) || '' AS x'';
FOR result IN EXECUTE cmd LOOP
return result.x;
END LOOP;
END;
'
LANGUAGE 'plpgsql' VOLATILE;

--
Oliver Elphick olly@lfix.co.uk
Isle of Wight http://www.lfix.co.uk/oliver
GPG: 1024D/A54310EA 92C8 39E7 280E 3631 3F0E 1EC0 5664 7A2F A543 10EA
========================================
"Whosoever therefore shall be ashamed of me and of my
words in this adulterous and sinful generation; of him
also shall the Son of man be ashamed, when he cometh
in the glory of his Father with the holy angels."
Mark 8:38

Try using EXECUTE.

http://www.postgresql.org/docs/7.4/static/plpgsql-
statements.html#PLPGSQL-STATEMENTS-EXECUTING-DYN

-tfo

--
Thomas F. O'Connell
Co-Founder, Information Architect
Sitening, LLC
http://www.sitening.com/
110 30th Avenue North, Suite 6
Nashville, TN 37203-6320
615-260-0005

On Oct 26, 2004, at 11:57 AM, Naeem Bari wrote: