Re: PostgreSQL OR performance

2008/11/6 Helio Campos Mello de Andrade <helio(dot)campos(at)gmail(dot)com>

> For what i see in four OR-plan.txt tou are doing too much "sequencial scan"
> . Create some indexes for those tables using the fields that you use an it
> may help you.
>
> OBS: If you already have lots of indexes in your tables it may be a good
> time for you re-think your strategy because it´s ot working.
> Tips:
> 1 - create indexes for the tables with the fields that you will use in
> the query if it is your most important query. If you have others querys that
> are used please post those here and we can help you to desing a better plan.

As you can see from other plans, it do have all the indexes to perform it's
work fast (when given part by part). It simply do not wish to use them. My
question: Is this a configuration problem or postgresql optimizer simply
can't do such a query rewrite?

Actually I did rewrite the query to work properly as you can see from
union-plan.txt. My question is if postgresql can do this automatically
because such a rewrite is not always easy/possible (esp. for generated
queries)?