From rad_cs_2006@yahoo.com Mon Apr  11 23:02:51 2011
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Date: Mon, 11 Apr 2011 16:02:31 -0700 (PDT)
From: Radhya sahal <rad_cs_2006@yahoo.com>
Subject: how explain works
To: pgsql-performance group <pgsql-performance@postgresql.org>
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--0-717010439-1302562951=:55807
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Dear ,all=0Aplz could any one help me !!!=0Ahow explian works as math equat=
ions to estimate=A0cost with=A0 constatn query =0Aparameters=0Asuch as cpu_=
tuple cost ,random page cost ...etc=0A=A0i want maths=A0 expression=A0 in o=
rder to know how these parameters will=A0effect in =0Acost ???=0Aplease any=
 one can help me ??=0A=A0=0A=A0=0ARegards=0ARadhya...
--0-717010439-1302562951=:55807
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<html><head><style type=3D"text/css"><!-- DIV {margin:0px;} --></style></he=
ad><body><div style=3D"font-family:times new roman, new york, times, serif;=
font-size:14pt;color:#ff00ff;"><DIV><FONT color=3D#2d2d2d size=3D4 face=3D"=
times new roman, new york, times, serif">Dear ,all</FONT></DIV>=0A<DIV><FON=
T color=3D#2d2d2d size=3D4 face=3D"times new roman, new york, times, serif"=
>plz could any one help me !!!</FONT></DIV>=0A<DIV><FONT color=3D#2d2d2d si=
ze=3D4 face=3D"times new roman, new york, times, serif">how explian works a=
s math equations to estimate&nbsp;cost with&nbsp; constatn query parameters=
</FONT></DIV>=0A<DIV><FONT color=3D#2d2d2d size=3D4 face=3D"times new roman=
, new york, times, serif">such as cpu_tuple cost ,random page cost ...etc</=
FONT></DIV>=0A<DIV><FONT color=3D#2d2d2d size=3D4 face=3D"times new roman, =
new york, times, serif">&nbsp;i want maths&nbsp; expression<SPAN id=3Dresul=
t_box lang=3Dar class=3Dshort_text><SPAN class=3Dhps title=3D"Click for alt=
ernate translations" closure_uid_yndlsn=3D"119"><SPAN class=3Dgt-spell-corr=
ected-text closure_uid_yndlsn=3D"120"><B><I>&nbsp; </I></B></SPAN></SPAN></=
SPAN>in order to know how these parameters will&nbsp;effect in cost ???</FO=
NT></DIV>=0A<DIV><FONT color=3D#2d2d2d size=3D4 face=3D"times new roman, ne=
w york, times, serif">please any one can help me ??</FONT></DIV>=0A<DIV><FO=
NT color=3D#2d2d2d size=3D4 face=3D"times new roman, new york, times, serif=
"></FONT>&nbsp;</DIV>=0A<DIV><FONT color=3D#2d2d2d size=3D4></FONT>&nbsp;</=
DIV>=0A<DIV><FONT color=3D#2d2d2d size=3D4>Regards</FONT></DIV>=0A<DIV><FON=
T color=3D#2d2d2d size=3D4>Radhya...</FONT></DIV></div></body></html>
--0-717010439-1302562951=:55807--



From npboley@gmail.com Mon Apr  11 23:09:34 2011
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In-Reply-To: <64088.55807.qm@web38604.mail.mud.yahoo.com>
References: <64088.55807.qm@web38604.mail.mud.yahoo.com>
From: Nathan Boley <npboley@gmail.com>
Date: Mon, 11 Apr 2011 16:09:07 -0700
Message-ID: <BANLkTikjvRxdZTPjNEPW_uNv=Y55r+tPDg@mail.gmail.com>
Subject: Re: how explain works
To: Radhya sahal <rad_cs_2006@yahoo.com>
Cc: pgsql-performance group <pgsql-performance@postgresql.org>
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> how explian works as math equations to estimate=A0cost with=A0 constatn q=
uery
> parameters
> such as cpu_tuple cost ,random page cost ...etc
> =A0i want maths=A0 expression=A0 in order to know how these parameters wi=
ll=A0effect
> 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