Re: Pipelined functions in Postgres

Hello Shoaib,

I know the SETOF funcitons. I want to  simulate (somehow) producer/consumer relationship with SETOF(pipelined) functions.  The first  (producer )function generates records (just like your test_pipe function), and the second function consumers the records , produced by the first function. The second function can be rows/records producer for another consumer functions e.g. it should looks like(or similar)

select * from consumer_function(  producer_function(param1, param2, ...));

 

What I want to achieve is to impelement some ETL logic in consumer_functions (they could be chained, of course).

The main idea is to read source  DWH tables once (in  producer_function, for example), and to process the rowsets

in the consumer functions. I want to avoid writing to intermediate tables while performing ETL processing .

Is this possible with SETOF functions ?

 

Best Regards

Milen

-----Original Message-----
From: pgsql-performance-owner@postgresql.org [mailto:pgsql-performance-owner@postgresql.org] On Behalf Of Shoaib Mir
Sent: Tuesday, September 19, 2006 11:05 PM
To: Milen Kulev
Cc: pgsql-performance@postgresql.org
Subject: Re: [PERFORM] Pipelined functions in Postgres

I think pipelined functions are code you can pretend is a database table.

For example you can do it like this in Oracle:

select * from PLSQL_FUNCTION;

You can achieve something similar in PostgreSQL using RETURN SETOF functions like this:

CREATE OR REPLACE FUNCTION test_pipe (int)
    RETURNS SETOF RECORD AS
$$
DECLARE
    v_rec    RECORD;
BEGIN
    FOR temp_rec IN (SELECT col FROM table where col > 10)
    LOOP
        RETURN NEXT v_rec;
    END LOOP;
    RETURN;
END;
$$ LANGUAGE plpgsql;

This function can be called like this:

SELECT * FROM test_pipe(10) AS tbl (col int);
 
Hope this helps...

Thanks,
--
Shoaib Mir
EnterpriseDB (www.enterprisedb.com)

On 9/20/06, Milen Kulev <makulev@gmx.net> wrote:

Hello Lister,
I am curios whether I can emulate the Oracle pipelined functions functionality in PG too (using RETURN NEXT ). For more
information and examples about Oracle pipelined functions see:
http://asktom.oracle.com/pls/ask/f?p=4950:8:8127757633768425921::NO::F4950_P8_DISPLAYID,F4950_P8_CRITERIA:4447489221109

I have used  pipeline functions in DWH enviromnent  with success and would like
To use similar concept in PG too.

Any help, examples , links and  shared experiences would be greately appreciated.

Best Regards.
Milen


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