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Re: Index Page Split logging

From: "Gokulakannan Somasundaram" <gokul007(at)gmail(dot)com>
To: "Martijn van Oosterhout" <kleptog(at)svana(dot)org>
Cc: "Simon Riggs" <simon(at)2ndquadrant(dot)com>, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Index Page Split logging
Date: 2008-01-02 13:48:39
Message-ID: 9362e74e0801020548x12c69414vfb458cead99b9589@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Jan 2, 2008 6:24 PM, Martijn van Oosterhout <kleptog(at)svana(dot)org> wrote:

> On Wed, Jan 02, 2008 at 04:46:11PM +0530, Gokulakannan Somasundaram wrote:
> > > All indexes are done by user-defined functions, even b-trees. People
> can
> > > make their own b-tree indexes by defining an operator class. Note that
> > > "user-defined" is this case means anything called via the fmgr
> > > interface.
> >
> > Again, i think i have one more wrong understanding. My understanding is,
> > We are discussing about user-defined functions because, they might be
> > actually be mutable functions, but the user might have classified as
> > immutable.
>
> This is where it gets a bit beyond by depth, so someone may have to
> correct me. The point is that during the recovery the system is not yet
> fully running and not everything works yet. For example, what happens
> if the system crashed halfway through updating a page in pg_proc and
> that page needs to be recovered from WAL. Yet to insert into the index
> you need to be able to read pg_am, pg_amproc, pg_proc at least,
> probably more.
>
> The point being, you can't rely on anything except WAL during recovery.
>
> Thanks a lot for the nice explanation.  That was something new for
me....:((


-- 
Thanks,
Gokul.

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