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Re: COPY LOCK for WAL bypass

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, Chris Browne <cbbrowne(at)acm(dot)org>, pgsql-patches(at)postgresql(dot)org
Subject: Re: COPY LOCK for WAL bypass
Date: 2005-12-21 13:18:15
Message-ID: 200512211318.jBLDIFQ03925@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-patches
Jim C. Nasby wrote:
> On Mon, Dec 19, 2005 at 07:51:54AM +0000, Simon Riggs wrote:
> > On Sun, 2005-12-18 at 22:03 -0500, Chris Browne wrote:
> > > simon(at)2ndquadrant(dot)com (Simon Riggs) writes:
> > > > On Sat, 2005-12-10 at 12:07 +0000, Simon Riggs wrote:
> > > >> Following patch implements COPY ... FROM ... LOCK
> > > >
> > > > Patch now updated so that it includes an additional optimization of
> > > > COPY, so that WAL will not be written in the transaction that created
> > > > the table.
> > > >
> > > > This now gives two fast paths for COPY:
> > > > 1) COPY LOCK
> > > > 2) COPY in same transaction (e.g. reloading a pg_dump)
> > > 
> > > I presume that if this doesn't go into WAL, that means that this kind
> > > of update wouldn't play with PITR, right?
> > 
> > You're right.
> > 
> > PITR is designed for normal production use, rather than initial loading.
> > It is also fairly common to turn PITR off permanently in larger data
> > warehouses, which is also where these optimizations are aimed.
> 
> Hrm... I'd say we need an option to disable the fast-copy then, in case
> you wanted the copy to make it into PITR. Or perhaps we just disallow
> the fast-copy when PITR is in use. I believe that's what other databases
> do...

Right, just disable with a clear error message.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

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