Date: Fri, 8 Nov 2019 14:58:30 +0100
From: Christoph Berg <myon@debian.org>
To: Julien Rouhaud <rjuju123@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Monitoring disk space from within the server
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Re: Julien Rouhaud 2019-11-08 <CAOBaU_Zu6RP6-mHyA_J9-xkxJe0tarTVqU9TFza+tCPKUxsjiA@mail.gmail.com>
> The related function on Windows is apparently GetDiskFreeSpaceA [1].

There's a link to GetDiskFreeSpaceExA() which seems much easier to use
because it accepts any directory on the drive in question:

https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-getdiskfreespaceexa

> It'll probably be quite hard to get something consistent for most of
> counters, so probably pg_tablespace_(disk_)space is the best name,
> providing only total size and free size?

So, how about:

pg_tablespace_disk_space -> total_bytes | free_bytes

The inode numbers are probably not very interesting in a PG tablespace
as we don't create that many files. Or do we think including these
counters (on UNIX) makes sense?

There's precedents for leaving fields NULL where not supported by the
OS, for example pg_stat_file() returns "change" on UNIX only, and
"creation" on Windows only.

Christoph