Re: [PING] fallocate() causes btrfs to never compress postgresql files

Thomas Munro <thomas.munro@gmail.com>

From: Thomas Munro <thomas.munro@gmail.com>

To: Dimitrios Apostolou <jimis@gmx.net>

Cc: Tomas Vondra <tomas@vondra.me>, pgsql-hackers@lists.postgresql.org, Andres Freund <andres@anarazel.de>, Melanie Plageman <melanieplageman@gmail.com>, Heikki Linnakangas <hlinnaka@iki.fi>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, David Rowley <dgrowleyml@gmail.com>

Date: 2025-05-31T14:32:45Z

Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

Add file_extend_method=posix_fallocate,write_zeros.
- e37b59802846 16.12 landed
- 4dac22aa10d2 17.8 landed
- f94e9141a0bb 19 (unreleased) landed
- 33e3de6d77e8 18.2 landed
Add smgrzeroextend(), FileZero(), FileFallocate()
- 4d330a61bb19 16.0 cited

Or for a completely different approach: I wonder if ftruncate() would
be more efficient on COW systems anyway.  The minimum thing we need is
for the file system to remember the new size, 'cause, erm, we don't.
All the rest is probably a waste of cycles, since they reserve real
space (or fail to) later in the checkpointer or whatever process
eventually writes the data out.