Hi,
I also tested the patch on Linux mint 22.1 with the btrfs and ext4 partitions. I generated some data and the outcome looks good:
postgres=# \db+
List of tablespaces
Name | Owner | Location | Access privileges | Options | Size | Free | Description
------------------+----------+---------------------------+-------------------+---------+---------+---------+-------------
pg_default | postgres | | | | 1972 MB | 29 GB |
pg_global | postgres | | | | 556 kB | 29 GB |
tablespace_test2 | postgres | /media/said/queryme/pgsql | | | 3147 MB | 1736 GB |
Numbers are the same as if I were executing the command: df -h
tablespace_test2 was the ext4 partition on usb stick.
Numbers are correct.
Said
On 2025-03-13 14 h 10, Christoph Berg wrote:
Hi,
I'm picking up a 5 year old patch again:
https://www.postgresql.org/message-id/flat/20191108132419.GG8017%40msg.df7cb.de
Users will be interested in knowing how much extra data they can load
into a database, but PG currently does not expose that number. This
patch introduces a new function pg_tablespace_avail() that takes a
tablespace name or oid, and returns the number of bytes "available"
there. This is the number without any reserved blocks (Unix, f_avail)
or available to the current user (Windows).
(This is not meant to replace a full-fledged OS monitoring system that
has much more numbers about disks and everything, it is filling a UX
gap.)
Compared to the last patch, this just returns a single number so it's
easier to use - total space isn't all that interesting, we just return
the number the user wants.
The free space is included in \db+ output:
postgres =# \db+ List of tablespaces Name │ Owner │ Location │ Access privileges │ Options │ Size │ Free │ Description
────────────┼───────┼──────────┼───────────────────┼─────────┼─────────┼────────┼───────────── pg_default │ myon │ │ ∅ │ ∅ │ 23 MB │ 538 GB │ ∅ pg_global │ myon │ │ ∅ │ ∅ │ 556 kB │ 538 GB │ ∅ spc │ myon │ /tmp/spc │ ∅ │ ∅ │ 0 bytes │ 31 GB │ ∅
(3 rows)
The patch has also been tested on Windows.
TODO: Figure out which systems need statfs() vs statvfs()
Christoph
