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Re: Catalog/Metadata consistency during changeset extraction from wal

From: David Fetter <david(at)fetter(dot)org>
To: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Catalog/Metadata consistency during changeset extraction from wal
Date: 2012-06-26 18:11:54
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Lists: pgsql-hackers
On Mon, Jun 25, 2012 at 01:50:54PM -0500, Kevin Grittner wrote:
> Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> > I am not sure were going to get all that into 9.3.
> Sure, that was more related to why I was questioning how much these
> use cases even *could* integrate -- whether it even paid to
> *consider* these use cases at this point.  Responses from Robert and
> you have pretty much convinced me that I was being overly
> pessimistic on that.
> One fine point regarding before and after images -- if a value
> doesn't change in an UPDATE, there's no reason to include it in both
> the BEFORE and AFTER tuple images, as long as we have the null
> column bitmaps -- or some other way of distinguishing unchanged from
> NULL.  (This could be especially important when the unchanged column
> was a 50 MB bytea.)

How about two bitmaps: one telling which columns are actually there,
the other with NULLs?

David Fetter <david(at)fetter(dot)org>
Phone: +1 415 235 3778  AIM: dfetter666  Yahoo!: dfetter
Skype: davidfetter      XMPP: david(dot)fetter(at)gmail(dot)com
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