[PoC PATCH] Parallel dump to /dev/null

Hi,

dumping a database to /dev/null via pg_dump is (AFAIK) one recommended
way to check for corruption. However, dumping to /dev/null is currently
not supported in directory mode which makes it not possible to dump to
/dev/null in parallel.

I had a look at this, and it appears it would suffice to just override
the few spots in pg_backup_directory.c which assemble filenames in the
target directory to revert to '/dev/null' (or 'NUL' on Windows).

The attached proof-of-concept patch does that, and it seems to work; I'm
getting some nice speedups on a 170 GB test database:

$ time pg_dump -Fc -Z0 -f /dev/null TESTDB
real 32m45.120s
[...]
$ time pg_dump -Fd -j8 -Z0 -f /dev/null TESTDB
real 9m28.357s

Thoughts?

Michael

--
Michael Banck
Projektleiter / Senior Berater
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