Re: PostgreSQL as a local in-memory cache

From: Bruce Momjian
Subject: Re: PostgreSQL as a local in-memory cache
Date: ,
Msg-id: 201006291332.o5TDWTZ01574@momjian.us
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In response to: Re: PostgreSQL as a local in-memory cache  (Robert Haas)
Responses: Re: PostgreSQL as a local in-memory cache  ("Kevin Grittner")
Re: PostgreSQL as a local in-memory cache  (Robert Haas)
List: pgsql-performance

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PostgreSQL as a local in-memory cache  ("", )
 Re: PostgreSQL as a local in-memory cache  ("", )
  Re: PostgreSQL as a local in-memory cache  (Josh Berkus, )
   Re: PostgreSQL as a local in-memory cache  ("Pierre C", )
   Re: PostgreSQL as a local in-memory cache  (Dimitri Fontaine, )
    Re: PostgreSQL as a local in-memory cache  (Tom Lane, )
     Re: PostgreSQL as a local in-memory cache  (Bruce Momjian, )
      Re: PostgreSQL as a local in-memory cache  (Pavel Stehule, )
       Re: PostgreSQL as a local in-memory cache  (Bruce Momjian, )
      Re: PostgreSQL as a local in-memory cache  (Robert Haas, )
       Re: PostgreSQL as a local in-memory cache  (Dave Page, )
        Re: PostgreSQL as a local in-memory cache  (Tom Lane, )
         Re: PostgreSQL as a local in-memory cache  (Bruce Momjian, )
         Re: PostgreSQL as a local in-memory cache  (Dimitri Fontaine, )
       Re: PostgreSQL as a local in-memory cache  (Bruce Momjian, )
     Re: PostgreSQL as a local in-memory cache  (Bruce Momjian, )
      Re: PostgreSQL as a local in-memory cache  (Bruce Momjian, )
       Re: PostgreSQL as a local in-memory cache  (Robert Haas, )
        Re: PostgreSQL as a local in-memory cache  (Bruce Momjian, )
         Re: PostgreSQL as a local in-memory cache  ("Kevin Grittner", )
         Re: PostgreSQL as a local in-memory cache  (Robert Haas, )
          Re: PostgreSQL as a local in-memory cache  (Bruce Momjian, )
           Re: PostgreSQL as a local in-memory cache  (Tom Lane, )
            Re: PostgreSQL as a local in-memory cache  (Bruce Momjian, )
             Re: PostgreSQL as a local in-memory cache  (Jignesh Shah, )
              Re: PostgreSQL as a local in-memory cache  (Bruce Momjian, )
               Re: PostgreSQL as a local in-memory cache  (Brad Nicholson, )
                Re: PostgreSQL as a local in-memory cache  (Bruce Momjian, )
               Re: PostgreSQL as a local in-memory cache  (Jignesh Shah, )
                Re: PostgreSQL as a local in-memory cache  (Greg Smith, )
    Re: PostgreSQL as a local in-memory cache  ("Pierre C", )
     Re: PostgreSQL as a local in-memory cache  (Matthew Wakeling, )
      Re: PostgreSQL as a local in-memory cache  ("Pierre C", )
       Re: PostgreSQL as a local in-memory cache  (Josh Berkus, )
        Re: PostgreSQL as a local in-memory cache  (Rob Wultsch, )
         Re: PostgreSQL as a local in-memory cache  (Robert Haas, )
          Re: PostgreSQL as a local in-memory cache  (Josh Berkus, )
           Re: PostgreSQL as a local in-memory cache  (Pavel Stehule, )
            Re: PostgreSQL as a local in-memory cache  ("Joshua D. Drake", )
             Re: PostgreSQL as a local in-memory cache  (Pavel Stehule, )
              Re: PostgreSQL as a local in-memory cache  ("A.M.", )
               Re: PostgreSQL as a local in-memory cache  (Pavel Stehule, )
            Re: PostgreSQL as a local in-memory cache  (Josh Berkus, )
             Re: PostgreSQL as a local in-memory cache  (Pavel Stehule, )
            Re: PostgreSQL as a local in-memory cache  ("Joshua D. Drake", )
      Re: PostgreSQL as a local in-memory cache  (Josh Berkus, )
    Re: PostgreSQL as a local in-memory cache  (Josh Berkus, )
     Re: PostgreSQL as a local in-memory cache  (Tom Lane, )
   Re: PostgreSQL as a local in-memory cache  (Greg Smith, )
   Re: PostgreSQL as a local in-memory cache  (Robert Haas, )
 Re: PostgreSQL as a local in-memory cache  (Dave Crooke, )
  Re: PostgreSQL as a local in-memory cache  (Craig James, )

Robert Haas wrote:
> On Mon, Jun 28, 2010 at 5:57 PM, Bruce Momjian <> wrote:
> >> The patch also documents that synchronous_commit = false has
> >> potential committed transaction loss from a database crash (as well as
> >> an OS crash).
>
> Is this actually true?

I asked on IRC and was told it is true, and looking at the C code it
looks true.  What synchronous_commit = false does is to delay writing
the wal buffers to disk and fsyncing them, not just fsync, which is
where the commit loss due to db process crash comes from.

--
  Bruce Momjian  <>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + None of us is going to be here forever. +


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From: Bruce Momjian
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Subject: Re: PostgreSQL as a local in-memory cache