Re: dynamic functions

hi sean,

i tried the FOR-IN-EXECUTE methode before but i couldn't manage it. now i
got it. it's tricky and the code looks strange. the first trick is (you cant
use an integer as a result because in that case pgplsql would expext a
'normal' FOR i IN 2..5 LOOP.) i had to create a dummy type for the result.

CREATE TYPE attribute.temp AS (err INTEGER);

And then I misused an empty FOR LOOP as an assignment ...

###
CREATE OR REPLACE FUNCTION attribute.validate(TEXT,TEXT) RETURNS INTEGER AS
'
DECLARE
tmp RECORD;
cmd TEXT;
BEGIN
cmd := ''SELECT * FROM '' || $1 || ''('' || quote_literal($2) || '')'';
FOR tmp IN EXECUTE cmd LOOP END LOOP;
RETURN tmp.err;
END; '
LANGUAGE plpgsql;
###

but it works ...

thanks for the inspiration

sepp

its a problem that there is no example in the documentation for this
workaround :-<

>From: Sean Davis <sdavis2(at)mail(dot)nih(dot)gov>
>To: "Robert Wimmer" <seppwimmer(at)hotmail(dot)com>
>CC: pgsql-interfaces(at)postgresql(dot)org
>Subject: Re: [INTERFACES] dynamic functions
>Date: Thu, 5 May 2005 18:30:40 -0400
>
>From the manual, you can use FOR-IN-EXECUTE or a cursor for pl/pgsql:
>
>The results from SELECT commands are discarded by EXECUTE, and SELECT INTO
>is not currently supported within EXECUTE. So there is no way to extract a
>result from a dynamically-created SELECT using the plain EXECUTE command.
>There are two other ways to do it, however: one is to use the
>FOR-IN-EXECUTE loop form described in Section 35.7.4, and the other is to
>use a cursor with OPEN-FOR-EXECUTE, as described in Section 35.8.2.
>
>Does this help any? If not, they you could use another procedure language
>like pl/perl or others. With many of them, you can build the SQL query,
>then execute it and get the returned results. Again, see the manual
>section for pl/perl (for example,
>http://www.postgresql.org/docs/8.0/static/plperl-database.html) and others.
>
>Sean
>
>
>On May 5, 2005, at 5:49 PM, Robert Wimmer wrote:
>
>>hi ,
>>
>>is there any way to build "dynamic functions" in plpgsql ?
>>
>>my problem is, i have a table defining attributes like
>>
>>CREATE TABLE attribute.attribute (
>> name NAME PRIMARY KEY,
>> descr VARCHAR(256),
>> regex VARCHAR(50) NOT NULL,
>> minlen INTEGER NOT NULL DEFAULT 0,
>> maxlen INTEGER NOT NULL DEFAULT 64
>> -- validate NAME // not implemented
>> );
>>
>>and a function like
>>
>>CREATE OR REPLACE FUNCTION
>>attribute.match(TEXT,TEXT,BOOLEAN) RETURNS INTEGER AS '
>>
>>.. check the value (against the regex etc) ..
>>
>>END; ' LANGUAGE plpgsql
>>
>>in some cases i would like to check the values also against a function for
>>example
>>
>>CREATE FUNCTION attribute.check_range(TEXT) RETURNS INTEGER AS '
>>BEGIN
>> IF $1 ... THEN RETURN -1; END IF;
>> RETURN 0;
>>END; '
>>....
>>
>>so that i can do the following in my match function
>>
>>CREATE OR REPLACE FUNCTION
>>attribute.match(TEXT,TEXT,BOOLEAN) RETURNS INTEGER AS '
>>
>> .. check the value (against the regex etc) ..
>> IF attrib.validate NOT IS NULL THEN
>> cmd := atrib.validate || ''('' $1 '')'' ||;
>> -- ??
>> -- EXECUTE ''SELECT '' || cmd; // SELECT does not work in EXECUTE
>> -- ??
>> END IF
>>
>>END; ' LANGUAGE plpgsql
>>
>>is there a way to get a result back from EXECUTE ?
>>
>>i hope you can understand my description of the problem
>>i am using postgresQL 7.4 on debian
>>
>>thanx
>>
>>sepp
>>
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