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Message-ID: <4C4DFD95.4000901@lbl.gov>
Date: Mon, 26 Jul 2010 14:26:45 -0700
From: Gerald Fontenay <gvfontenay@lbl.gov>
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To: pgsql-performance@postgresql.org
CC: Gerald Fontenay <gvfontenay@lbl.gov>
Subject: Re: Strange explain on partitioned tables
References: <4C47F8C8.10005@edd.fr> <4C484874.3060609@2ndquadrant.com>	
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Joshua D. Drake wrote:
> On Fri, 2010-07-23 at 15:03 -0700, Gerald Fontenay wrote:
>   
>>> The PostgreSQL partitioning system is aimed to support perhaps a 
>>> hundred inherited tables.  You can expect to get poor performance on 
>>> queries if you create 1000 of them. 
>>>       
>> Hi,
>>
>> Why is that you would expect poor performance for say 1000 or more? I 
>> have a ~1000 inherited tables and I don't see any significant slowdowns. 
>> I only ever access a single inherited table at a time though in this 
>> situation. I suppose I am using inheritance only for organization in 
>> this case...
>>     
>
> It is variable based on workload and as I recall has to do with the
> planning time. As the number of children increases, so does the planning
> time.
>
> Joshua D. Drake
>
>
>   
Thank you for your response. So if I query only my target child table, 
this should be "just like" any other single table wrt planning right? I 
have thousands of these tables. (I suppose that I'm only using 
inheritance for the sake of organization in this situation...)

Thanks!
Gerald

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Joshua D. Drake wrote:
<blockquote
 cite="mid1279923370.9866.37.camel@jd-desktop.unknown.charter.com"
 type="cite">
  <pre wrap="">On Fri, 2010-07-23 at 15:03 -0700, Gerald Fontenay wrote:
  </pre>
  <blockquote type="cite">
    <blockquote type="cite">
      <pre wrap="">The PostgreSQL partitioning system is aimed to support perhaps a 
hundred inherited tables.  You can expect to get poor performance on 
queries if you create 1000 of them. 
      </pre>
    </blockquote>
    <pre wrap="">Hi,

Why is that you would expect poor performance for say 1000 or more? I 
have a ~1000 inherited tables and I don't see any significant slowdowns. 
I only ever access a single inherited table at a time though in this 
situation. I suppose I am using inheritance only for organization in 
this case...
    </pre>
  </blockquote>
  <pre wrap=""><!---->
It is variable based on workload and as I recall has to do with the
planning time. As the number of children increases, so does the planning
time.

Joshua D. Drake


  </pre>
</blockquote>
<font size="+1"><font face="Courier New, Courier, monospace">Thank you
for your response. So if I query only my target child table, this
should be "just like" any other single table wrt planning right? I have
thousands of these tables. (I suppose that I'm only using inheritance
for the sake of organization in this situation...)<br>
<br>
Thanks!<br>
Gerald<br>
</font></font>
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