Re: [SQL] Simple Optimization Problem

I have added this to our TODO list as:

process const=const parts of OR clause first

> I need to run a report using some parameters that are optional, I'm
> doing this by labeling "0" as the optional value. IE here is a
> simplified example:
>
> CREATE TABLE po (po_id int4 PRIMARY KEY, data text);
> (insert a bunch of rows)
>
> ftc=> explain select * from po where po_id=8888;
> NOTICE: QUERY PLAN:
>
> Index Scan using ipo_poid_units on po (cost=2.05 size=1 width=94)
>
> EXPLAIN
>
> ftc=> explain select * from po where (po_id=8888 or 0=8888);
> NOTICE: QUERY PLAN:
>
> Seq Scan on po (cost=449.96 size=1751 width=94)
>
> EXPLAIN
>
> I was hoping PostgreSQL could optimize out the boolean condition
> given in the where clause, but it causes it to disregard the index
> instead of throwing out 0=8888 in the first stage.
>
> This is the only way I can think to do this, I have crystal reports
> send through the SQL instead of doing the whole thing itself(Which
> involves returning all possible rows... Sigh)... This query is taking 20
> minutes as a result... Is there any hope in 6.5 of the optimizer
> handling this better?
>
> David Secret
> MIS Director
> Kearney Development Co., Inc.
>
>
>

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