Message-ID: <4DA23CFE.7020109@fuzzy.cz>
Date: Mon, 11 Apr 2011 01:27:58 +0200
From: Tomas Vondra <tv@fuzzy.cz>
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To: pgsql-performance@postgresql.org
Subject: Re: optimizer parameters
References: <77760.3733.qm@web38606.mail.mud.yahoo.com>
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There's a quite nice description in the docs:

http://www.postgresql.org/docs/9.0/interactive/row-estimation-examples.html

and a some more details for indexes:

http://www.postgresql.org/docs/9.0/interactive/index-cost-estimation.html

A bit more info about how this is used is available in this presentation:

http://momjian.us/main/writings/pgsql/internalpics.pdf

But if you need more details, then I quess the best approach to get it
is to read the sources (search for the cost estimation etc.).

regards
Tomas

Dne 10.4.2011 20:22, Radhya sahal napsal(a):
> Dear ,all
> i would to ask you about how postgresql optimizer parameters :-
> 1- random page cost
> 
> 2- cpu tuple cost
> 
> 3- cpu operator cost
> 
> 4- cpu index tuple cost
> 
> 5- effective cache size
> 
> play as parameters in cost estimator equation 
> 
> i imagine that cost function is the same as
> 
> f(x,y,z,....)=ax+by......
> 
> cost(cpu tuple cost,cpu operator cost,....)
> 
> can any one help me to know the equation that cost estimator used it..
> 
> My regard
> 
> Radhya,,,,
> 
>  
>