Re: Optimizing queries

Scott Marlowe wrote:
> On Tue, 2006-08-08 at 12:49, Patrice Beliveau wrote:
>
>> Hi,
>>
>> I have a query that use a function and some column test to select row.
>> It's in the form of:
>>
>> SELECT * FROM TABLE
>> WHERE TABLE.COLUMN1=something
>> AND TABLE.COLUMN2=somethingelse
>> AND function(TABLE.COLUMN3,TABLE.COLUMN4) > 0;
>>
>> The result of the function does NOT depend only from the table, but also
>> from some other tables.
>>
>> Since it's long to process, I've add some output to see what's going on.
>> I find out that the function process every row even if the row should be
>> rejected as per the first or the second condition. Then , my question
>> is: Is there a way to formulate a query that wont do all the check if it
>> does not need to do it ? Meaning that, if condition1 is false then it
>> wont check condition2 and that way the function will only be called when
>> it's really necessary.
>>
>
> What version of postgresql are you running? It might be better in later
> versions. The standard fix for such things is to use a subquery...
>
> select * from (
> select * from table where
> col1='something'
> and col2='somethingelse'
> ) as a
> where function(a.col3,a.col4) > 0;
>
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>
>
Thanks for the answer, but it does not work, maybe I did something wrong

First, I'm using version 8.1.3

This is what I did:

select * from (
select * from sales_order_delivery
where sales_order_id in (
select sales_order_id from sales_order
where closed=false
)
) as a where outstandingorder(sales_order_id, sales_order_item,
date_due) > 0;

Some output that I've create look like
INFO: so:03616 soi:1 date:1993-12-23
INFO: so:09614 soi:1 date:1998-06-04

which are the three arguments passed to the function "outstandingorder",
but sales_order 03616 and 09614 are closed.

What's wrong ??

Thanks