Faq vacuum messages

[TheVillageGuy]

Add sql query to free up disk space after deleting messages

[e-five256]

Realistically I'm not sure why the command does a DELETE FROM table rather than TRUNCATE table which frees disk space immediately (and also is instant, as it doesn't actually have to scan the table it's far faster)

TRUNCATE quickly removes all rows from a set of tables. It has the same effect as an unqualified DELETE on each table, but since it does not actually scan the tables it is faster. Furthermore, it reclaims disk space immediately, rather than requiring a subsequent VACUUM operation. This is most useful on large tables.

[e-five256]

I guess one is unqualified while the other, queue_name = dead, is not, so perhaps it's fine to leave as is and just call out what even the truncate docs mention, requires a vacuum to mark as freed

(There's a lot of finer details here in regards to how postgres marks space as free and what you have to do to actually return it to the OS, I don't want to super get into that but I think this is fine for now and people can always do more research reading the docs (specifically the "However, extra space is not returned to the operating system" section))