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Re: dynamic functions

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: dynamic functions
Date: 2005-05-05 22:30:40
Message-ID: 172293c304a9b54a333897da51566c39@mail.nih.gov (view raw or flat)
Thread:
Lists: pgsql-interfaces
 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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