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Re: PostgreSQL as a local in-memory cache

From: Dimitri Fontaine <dfontaine(at)hi-media(dot)com>
To: Josh Berkus <josh(at)agliodbs(dot)com>
Cc: postgres performance list <pgsql-performance(at)postgresql(dot)org>
Subject: Re: PostgreSQL as a local in-memory cache
Date: 2010-06-17 19:01:19
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance

Josh Berkus <josh(at)agliodbs(dot)com> writes:
> 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)

Well I guess I'd prefer a per-transaction setting, allowing to bypass
WAL logging and checkpointing. Forcing the backend to care itself for
writing the data I'm not sure is a good thing, but if you say so.

Then you could have the GUC set for a whole cluster, only a database
etc. We already have synchronous_commit to trade durability against
performances, we could maybe support protect_data = off too.

The d) point I'm not sure still applies if you have per transaction
setting, which I think makes the most sense. The data you choose not to
protect is missing at restart, just add some way to register a hook
there. We already have one (shared_preload_libraries) but it requires
coding in C. 

Calling a user function at the end of recovery and before accepting
connection would be good I think. A user function (per database) is
better than a script because if you want to run it before accepting
connections and still cause changes in the database…


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Next:From: Tom LaneDate: 2010-06-17 19:38:30
Subject: Re: PostgreSQL as a local in-memory cache
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