Re: ask for review of MERGE

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Greg Smith <greg(at)2ndquadrant(dot)com>, Marko Tiikkaja <marko(dot)tiikkaja(at)cs(dot)helsinki(dot)fi>, Boxuan Zhai <bxzhai2010(at)gmail(dot)com>, Greg Stark <gsstark(at)mit(dot)edu>, pgsql-hackers(at)postgresql(dot)org, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Martijn van Oosterhout <kleptog(at)svana(dot)org>
Subject: Re: ask for review of MERGE
Date: 2010-11-12 18:04:03
Message-ID: 201011121804.oACI43o14633@momjian.us
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Kevin Grittner wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
> > rhaas=# create table concurrent (x integer primary key);
> > NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index
> > "concurrent_pkey" for table "concurrent"
> > CREATE TABLE
> > rhaas=# insert into x values (1);
> > rhaas=# begin;
> > BEGIN
> > rhaas=# insert into concurrent values (2);
> > INSERT 0 1
> >
> > <switch to a different window>
> >
> > rhaas=# update concurrent set x=x where x=2;
> > UPDATE 0
>
> That surprised me. I would have thought that the INSERT would have
> created an "in doubt" tuple which would block the UPDATE. What is
> the reason for not doing so?

When Kevin gets surprised, I get worried. LOL

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +

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