Orphaned files in base/[oid]

Hi all;

I am trying to track down a problem we are seeing that looks very similar
to bug #12050, and would certainly consider trying to contribute a fix if
we agree on one. (I am not sure we can, so absent that, the next question
is whether it makes sense to create a utility to fix the problem when it
comes up so that a dump/restore is not needed).

The system:
PostgreSQL 9.6.3
Gentoo Linux.

Problem:
The system this came up on is PostgreSQL 9.6.3 and has had repeated trouble
with disk space. Querying pg_database_size, as well as du on the
subdirectory of base/ show total usage to be around 3.8TB. Summing up the
size of the relations in pg_class though shows around 2.1TB.

Initial troubleshooting found around 150 GB of space in pg_temp which had
never been cleared and was at least several days old. Restarting the
server cleared these up.

Poking around the base/[oid] directory, I found a large number of files
which did not correspond with a pg_class entry. One of the apparent
relations was nearly 1TB in size.

What I think happened:
I think various pg_temp/* and orphaned relation files (In base/[oid]) were
created when PostgreSQL crashed due to running out of space in various
operations including creating materialised views.

So my question is if there is a way we can safely clean these up on server
restart? If not does it make sense to try to create a utility that can
connect to PostgreSQL, seek out valid files, and delete the rest?

--
Best Regards,
Chris Travers
Database Administrator

Tel: +49 162 9037 210 | Skype: einhverfr | www.adjust.com
Saarbrücker Straße 37a, 10405 Berlin