explanation of some configs

От: Thomas Finneid
Тема: explanation of some configs
Дата: ,
Msg-id: 498CDB41.1010007@fcon.no
(см: обсуждение, исходный текст)
Ответы: Re: explanation of some configs  ("Joshua D. Drake")
Список: pgsql-performance

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explanation of some configs  (Thomas Finneid, )
 Re: explanation of some configs  ("Joshua D. Drake", )
  Re: explanation of some configs  (Thomas Finneid, )
   Re: explanation of some configs  (justin, )
    Re: explanation of some configs  (Matthew Wakeling, )
     Re: explanation of some configs  (justin, )
      Re: explanation of some configs  (Robert Haas, )
      Re: explanation of some configs  (Matthew Wakeling, )
       Re: explanation of some configs  (justin, )
        Re: explanation of some configs  (Greg Smith, )
         Re: explanation of some configs  (justin, )
          Re: explanation of some configs  (Greg Smith, )
           Re: explanation of some configs  (justin, )
   Re: explanation of some configs  (Robert Haas, )

Hi

I am having some problem understanding the details of a couple of
configuration directives. Here  is what I think I understand it so far:

effective_cache_size
    - specifies in how many B/KB/MB will be used to cache data
      between pg and the OS?
    - what is actually cached and how it is actually used by the
           planner and how does it affect the planner and the queries?
      -in other words, when and why do I need to set this parameter?

checkpoint_segments
    - specifies the number of segments?
      size: number*16MB?
    - means when number of WAL segments has filled up and matches
           checkpoint segment, dirty data is written to disk?
    - so it specifies how much data is stored in memory/wal before
           written to disk and therefore affects recoverability?

regards

thomas


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