Date: Thu, 5 Jan 2017 21:03:35 -0500
From: Bruce Momjian <bruce@momjian.us>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Pg Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Indirect indexes
Message-ID: <20170106020335.GA3063@momjian.us>
References: <20161229072807.b2p4ld55xmgwshhj@alvherre.pgsql>
 <20161230223530.gvu4azrsfqzr5eus@alvherre.pgsql>
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On Fri, Dec 30, 2016 at 07:35:30PM -0300, Alvaro Herrera wrote:
> Attached is v4, which fixes a couple of relatively minor bugs.  There
> are still things to tackle before this is committable, but coding review
> of the new executor node would be welcome.
> 
> The big remaining item is still fitting the PK data in TIDs 6 bytes.
> I've been looking at reworking the btree code to allow for an arbitrary
> size; it doesn't look impossible although it's going to be rather
> invasive.  Also, vacuuming: my answer continues to be that the killtuple
> interface should be good enough, but it's possible to vacuum the index
> separately from vacuuming the table anyway if you do a full scan and
> check the PK tuples for each indirect tuple.
> 
> This patch implements killtuple: a scan that sees an indirect tuple not
> returning anything from the heap marks the tuple as LP_DEAD.  Later,
> when the page is about to be split, those tuples are removed.
> 
> I also have a note in the code about not inserting an indirect tuple
> when an identical one already exists.  This is a correctness issue: we
> return duplicated heap rows in certain cases.

I still question the value of this patch as it requires user
configuration vs. more aggressive HOT/WARM updates.

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

+ As you are, so once was I.  As I am, so you will be. +
+                      Ancient Roman grave inscription +


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