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Re: Special column trivia

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Greg Smith <greg(at)2ndquadrant(dot)com>
Cc: pgsql-docs(at)postgresql(dot)org
Subject: Re: Special column trivia
Date: 2010-06-06 10:30:15
Message-ID: 17327.1275820215@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-docs
Greg Smith <greg(at)2ndquadrant(dot)com> writes:
> I was just reading 
> http://www.postgresql.org/docs/9.0/static/ddl-system-columns.html and 
> noted that the second part about the ctid being unstable:  "a row's ctid 
> will change if it is updated or moved by VACUUM FULL" is probably not 
> true anymore.  Is that worth updating?

It's still true.  VACUUM FULL still reassigns ctids.

> What got me reading that section was a rather weird documentation 
> question/addition from Edmund Horner.  He noted that the following works 
> on PG8.4 and 9.0:

> postgres=# select (row(1,2)).name;

This is the cast-a-composite-type-to-string-type issue that's come up in
several guises before, eg most recently at
http://archives.postgresql.org/pgsql-general/2010-05/msg01126.php

			regards, tom lane

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