Message-ID: <69cd4eb6a9686eab9319f864db15942ec06fe86c.camel@cybertec.at>
Subject: Re: checkpoint occurs very often when vacuum full running
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: Mariel Cherkassky <mariel.cherkassky@gmail.com>
Cc: Sergei Kornilov <sk@zsrv.org>, pgsql-admin@lists.postgresql.org
Date: Sat, 17 Nov 2018 20:28:10 +0100
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Mariel Cherkassky wrote:
> thank you for the explanation but I still got a few questions about this subject : 
> 1.By physical location of the data do you mean the location on disk of the objects?
> I mean i thought that the wal files containing the logical changes , for example
> If I run an update then the wal file will contain the update in some format.
> Can you explain then what exactly it contains and what you meant by physical ?

It does *not* contain the SQL executed - how'd that work with functions like
"random"?

Rather, the information is like "replace the 42 bytes from offset 99 of block 12
in file xy with these bytes: ...".

> 2.So If the vacuum full stopped in some brutal way (kill -9 or the disk run of space)
> does all the new data files that are created deleted or left on the storage as orphan files ?

In an out of space scenario, the files would get removed.

If you kill -9 the backend they will be left behind.

Yours,
Laurenz Albe
-- 
Cybertec | https://www.cybertec-postgresql.com