Re: 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(at)lfix(dot)co(dot)uk
Isle of Wight http://www.lfix.co.uk/oliver
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