Re: Any better plan for this query?.. - Mailing list pgsql-performance

From Alvaro Herrera
Subject Re: Any better plan for this query?..
Date
Msg-id 20090511225429.GM8689@alvh.no-ip.org
Whole thread Raw
In response to Re: Any better plan for this query?..  (Dimitri <dimitrik.fr@gmail.com>)
Responses Re: Any better plan for this query?..  (Dimitri <dimitrik.fr@gmail.com>)
List pgsql-performance
Dimitri escribió:
> Hi Aidan,
>
> thanks a lot for this detailed summary!
>
> So, why I don't use prepare here: let's say I'm testing the worst
> stress case :-)  Imagine you have thousands of such kind of queries -
> you cannot prepare all of them! :-)

Thousands?  Surely there'll be a dozen or three of most common queries,
to which you pass different parameters.  You can prepare thoseu

> Now, as you see from your explanation, the Part #2 is the most
> dominant - so why instead to blame this query not to implement a QUERY
> PLANNER CACHE??? - in way if any *similar* query is recognized by
> parser we simply *reuse* the same plan?..

This has been discussed in the past, but it turns out that a real
implementation is a lot harder than it seems.

--
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

pgsql-performance by date:

Previous
From: Dimitri
Date:
Subject: Re: Any better plan for this query?..
Next
From: Tom Lane
Date:
Subject: Re: Query planner making bad decisions