Postgres Pro
Downloads
Home   >   mailing lists

UNION and bad performance - Mailing list pgsql-performance

From Olivier Pala
Subject UNION and bad performance
Date
Msg-id 4D00B4DE.3030508@xgs-france.com
Whole thread Raw
Responses Re: UNION and bad performance  ("Marc Mamin" <M.Mamin@intershop.de>)
List pgsql-performance
Tree view
Hi,

I have a performance trouble with UNION query


First I have this view :

    SELECT a,b,c FROM table1, table2 WHERE jointure AND condition

    Result : 150 000 records in 1~2 s



Then, I adding an UNION into the same view :

    SELECT a,b,c FROM table1, table2 WHERE jointure AND condition
    UNION
    SELECT a,b,c FROM table3

    Result : 150 200 records in 6~7 s


Why, do I have bad performance only for 200 adding records ?

Thanks

SGBD : Postgres 8.3 et 8.4

pgsql-performance by date:

Previous
From: salima
Date:
Subject: Tunning Postgres
Next
From: "Marc Mamin"
Date:
Subject: Re: UNION and bad performance