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* Re: how explain works to Mr Nathan Boley
@ 2011-04-11 23:22 Radhya sahal <rad_cs_2006@yahoo.com>
2011-04-13 20:19 ` Re: how explain works to Mr Nathan Boley Tomas Vondra <tv@fuzzy.cz>
0 siblings, 1 reply; 2+ messages in thread
From: Radhya sahal @ 2011-04-11 23:22 UTC (permalink / raw)
To: Nathan Boley <npboley@gmail.com>; pgsql-performance
Thanks Mr Nathan Boley ,
i want these equations to solve thsese equtions of parameters and total time in
order to get each paramter formula
i need these formula in my experiments is very important to know the rate for
each parameter in total cost for plan.
Best
Radhya..
________________________________
From: Nathan Boley <npboley@gmail.com>
To: Radhya sahal <rad_cs_2006@yahoo.com>
Cc: pgsql-performance group <pgsql-performance@postgresql.org>
Sent: Mon, April 11, 2011 4:09:07 PM
Subject: Re: [PERFORM] how explain works
> how explian works as math equations to estimate cost with constatn query
> parameters
> such as cpu_tuple cost ,random page cost ...etc
> i want maths expression in order to know how these parameters will effect
> in cost ???
The expressions are complicated, and they are certainly not linear as
you seem to think from your previous post.
> please any one can help me ??
What do you need this for? If your goal is to optimize a real
application, then you should just vary the cost parameters and measure
the resulting change in query times. If your interests are academic,
there were some excellent suggestions for places to start in response
to your previous post.
Best,
Nathan
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: how explain works to Mr Nathan Boley
2011-04-11 23:22 Re: how explain works to Mr Nathan Boley Radhya sahal <rad_cs_2006@yahoo.com>
@ 2011-04-13 20:19 ` Tomas Vondra <tv@fuzzy.cz>
0 siblings, 0 replies; 2+ messages in thread
From: Tomas Vondra @ 2011-04-13 20:19 UTC (permalink / raw)
To: pgsql-performance
Dne 12.4.2011 01:22, Radhya sahal napsal(a):
> Thanks Mr Nathan Boley ,
> i want these equations to solve thsese equtions of parameters and total
> time in order to get each paramter formula
> i need these formula in my experiments is very important to know the
> rate for each parameter in total cost for plan.
> Best
> Radhya..
I don't think those equations are fully documented outside the source
code. If you really need the exact formulas, you'll have to dig into the
source codes and search there.
regards
Tomas
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2011-04-11 23:22 Re: how explain works to Mr Nathan Boley Radhya sahal <rad_cs_2006@yahoo.com>
2011-04-13 20:19 ` Tomas Vondra <tv@fuzzy.cz>
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