Re: IN list processing performance (yet again)

Bruno Wolff III wrote:

>On Wed, May 28, 2003 at 14:08:02 -0400,
>  Dave Tenny <tenny@attbi.com> wrote:
>  
>
>>Andreas Pflug wrote:
>>
>>I'm reminded to relay to the PostgreSQL devos that I might be able to do 
>>more in the  join or subquery department if
>>PostgreSQL had better performing MAX functions and a FIRST function for 
>>selecting rows from groups.
>>("Performing" being the operative word here, since the extensible 
>>architecture of PostgreSQL currently makes for poorly
>>performing MAX capabilities and presumably similar user defined 
>>aggregate functions).
>>    
>>
>
>Have you tried replacing max with a subselect that uses order by and limit?
>  
>

I'm uncertain how that would work, since somewhere in there I still need 
to elaborate on the
1000 items I want, and they're not necessarily in any particular range, 
nor do they bear any
contiguous group nature.

Also, IN (subquery) is a known performance problem in PGSQL, at least if 
the subquery is going to return many rows.
It's too bad, since I'm rather fond of subqueries, but I avoid them like 
the plague in PostgreSQL.

Perhaps I don't understand what you had in mind.