Re: UPDATEDs slowing SELECTs in a fully cached database

From: Tom Lane
Subject: Re: UPDATEDs slowing SELECTs in a fully cached database
Date: ,
Msg-id: 4752.1310570261@sss.pgh.pa.us
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In response to: Re: UPDATEDs slowing SELECTs in a fully cached database  ("Kevin Grittner")
Responses: Re: UPDATEDs slowing SELECTs in a fully cached database  (lars)
Re: UPDATEDs slowing SELECTs in a fully cached database  ("Kevin Grittner")
List: pgsql-performance

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UPDATEDs slowing SELECTs in a fully cached database  (lars, )
 Re: UPDATEDs slowing SELECTs in a fully cached database  (lars, )
  Re: UPDATEDs slowing SELECTs in a fully cached database  (Craig Ringer, )
   Re: UPDATEDs slowing SELECTs in a fully cached database  (lars hofhansl, )
    Re: UPDATEDs slowing SELECTs in a fully cached database  ("Kevin Grittner", )
     Re: UPDATEDs slowing SELECTs in a fully cached database  (lars, )
      Re: UPDATEDs slowing SELECTs in a fully cached database  ("Kevin Grittner", )
       Re: UPDATEDs slowing SELECTs in a fully cached database  (Merlin Moncure, )
        Re: UPDATEDs slowing SELECTs in a fully cached database  ("Kevin Grittner", )
         Re: UPDATEDs slowing SELECTs in a fully cached database  (Merlin Moncure, )
        Re: UPDATEDs slowing SELECTs in a fully cached database  (lars, )
         Re: UPDATEDs slowing SELECTs in a fully cached database  (lars, )
          Re: UPDATEDs slowing SELECTs in a fully cached database  (Ivan Voras, )
           Re: UPDATEDs slowing SELECTs in a fully cached database  (lars, )
            Re: UPDATEDs slowing SELECTs in a fully cached database  ("Kevin Grittner", )
             Re: UPDATEDs slowing SELECTs in a fully cached database  (lars, )
              Re: UPDATEDs slowing SELECTs in a fully cached database  ("Kevin Grittner", )
              Re: UPDATEDs slowing SELECTs in a fully cached database  (lars, )
               Re: UPDATEDs slowing SELECTs in a fully cached database  ("Kevin Grittner", )
                Re: UPDATEDs slowing SELECTs in a fully cached database  (lars, )
               Re: UPDATEDs slowing SELECTs in a fully cached database  ("Kevin Grittner", )
                Re: UPDATEDs slowing SELECTs in a fully cached database  (Tom Lane, )
                 Re: UPDATEDs slowing SELECTs in a fully cached database  (lars, )
                  Re: UPDATEDs slowing SELECTs in a fully cached database  (Merlin Moncure, )
                  Re: UPDATEDs slowing SELECTs in a fully cached database  (Jeff Janes, )
                 Re: UPDATEDs slowing SELECTs in a fully cached database  ("Kevin Grittner", )
                  Re: UPDATEDs slowing SELECTs in a fully cached database  (Tom Lane, )
                   Re: UPDATEDs slowing SELECTs in a fully cached database  ("Kevin Grittner", )
                    Re: UPDATEDs slowing SELECTs in a fully cached database  (Robert Klemme, )
                    Re: UPDATEDs slowing SELECTs in a fully cached database  (Tom Lane, )
                     Re: UPDATEDs slowing SELECTs in a fully cached database  (lars, )
                Re: UPDATEDs slowing SELECTs in a fully cached database  (lars, )
                 Re: UPDATEDs slowing SELECTs in a fully cached database  ("Kevin Grittner", )
                  Re: UPDATEDs slowing SELECTs in a fully cached database  (lars, )
                   Re: UPDATEDs slowing SELECTs in a fully cached database  (Jeff Janes, )
                    Re: UPDATEDs slowing SELECTs in a fully cached database  (lars, )
                     Re: UPDATEDs slowing SELECTs in a fully cached database  (Jeff Janes, )
                      Re: UPDATEDs slowing SELECTs in a fully cached database  (Greg Smith, )
              Re: UPDATEDs slowing SELECTs in a fully cached database  (Jeff Janes, )
               Re: UPDATEDs slowing SELECTs in a fully cached database  (Tom Lane, )
             Re: UPDATEDs slowing SELECTs in a fully cached database  (Merlin Moncure, )
              Re: UPDATEDs slowing SELECTs in a fully cached database  (lars, )
               Re: UPDATEDs slowing SELECTs in a fully cached database  (Merlin Moncure, )
                Re: UPDATEDs slowing SELECTs in a fully cached database  (Pavan Deolasee, )
                 Re: UPDATEDs slowing SELECTs in a fully cached database  (lars hofhansl, )
                  Re: UPDATEDs slowing SELECTs in a fully cached database  (Jeff Janes, )
            Re: UPDATEDs slowing SELECTs in a fully cached database  ("Kevin Grittner", )
 Re: UPDATEDs slowing SELECTs in a fully cached database  ("", )
  Re: UPDATEDs slowing SELECTs in a fully cached database  (Robert Klemme, )
   Re: UPDATEDs slowing SELECTs in a fully cached database  ("", )
   Re: UPDATEDs slowing SELECTs in a fully cached database  (lars, )
    Re: UPDATEDs slowing SELECTs in a fully cached database  ("Kevin Grittner", )
     Re: UPDATEDs slowing SELECTs in a fully cached database  (Merlin Moncure, )
 Re: UPDATEDs slowing SELECTs in a fully cached database  (Ivan Voras, )
  Re: UPDATEDs slowing SELECTs in a fully cached database  (Merlin Moncure, )
   Re: UPDATEDs slowing SELECTs in a fully cached database  (Ivan Voras, )
 Re: UPDATEDs slowing SELECTs in a fully cached database  (Lars, )

"Kevin Grittner" <> writes:
> ...  Jeff does raise a good point, though -- it seems odd
> that WAL-logging of this pruning would need to be synchronous.

Yeah, we need to get to the bottom of that.  If there's enough
shared_buffer space then it shouldn't be.

> We
> support asynchronous commits -- why not use that feature
> automatically for transactions where the only writes are this sort
> of thing.  Which raises an interesting question -- what happens to
> the timings if your SELECTs are done with synchronous_commit = off?
> I wonder if it would make any sense to implicitly use async commit
> for a transaction which is declared READ ONLY or which never
> acquires and XID?

Huh?  If there was never an XID, there's no commit WAL record, hence
nothing to make asynchronous.

            regards, tom lane


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From: Merlin Moncure
Date:
Subject: Re: UPDATEDs slowing SELECTs in a fully cached database
From: "Kevin Grittner"
Date:
Subject: Re: UPDATEDs slowing SELECTs in a fully cached database