Re: What does "Table rewrite" mean?

From: Michael Paquier <michael(dot)paquier(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: ilsa(at)ilsadee(dot)com, pgsql-docs(at)lists(dot)postgresql(dot)org
Subject: Re: What does "Table rewrite" mean?
Date: 2018-01-20 10:18:07
Message-ID: 20180120101807.GB1311@paquier.xyz
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On Fri, Jan 19, 2018 at 11:33:43AM -0500, Tom Lane wrote:
> It means reading the whole table and writing it out in some modified
> form (for instance, with some column transformed into a new datatype).
> It's not "dangerous" in any way ... but if you've got many GB of data in
> the table and you can't afford to have the table locked for a long time,
> then it's something to avoid.

Yeah that can be costly. Note that WAL corresponding to this data needs
to be generated as well.
--
Michael

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