Especially as, in repeated tests, PostgreSQL with persistence turned off
is just as fast as the fastest nondurable NoSQL database. And it has a
LOT more features.
An option to completely disable WAL for such use cases would make it a lot
faster, especially in the case of heavy concurrent writes.
Now, while fsync=off and tmpfs for WAL more-or-less eliminate the IO for
durability, they don't eliminate the CPU time.
Actually the WAL overhead is some CPU and lots of locking.
Which means that a caching version of PostgreSQL could be even faster.
To do that, we'd need to:
a) Eliminate WAL logging entirely
b) Eliminate checkpointing
c) Turn off the background writer
d) Have PostgreSQL refuse to restart after a crash and instead call an
exteral script (for reprovisioning)
Of the three above, (a) is the most difficult codewise.
Actually, it's pretty easy, look in xlog.c
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