From: | François Battail <francois(dot)battail(at)sipibox(dot)fr> |
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To: | PostgreSQL General <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: Optimizing a read-only database |
Date: | 2015-05-18 14:54:06 |
Message-ID: | 5559FD0E.9040308@sipibox.fr |
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Lists: | pgsql-general |
Le 18/05/2015 16:38, William Dunn a écrit :
Thank you William,
> * With read-only work loads you can make shared_buffers very large,
> like 40% of RAM available to the database. Usually you would keep it
> lower because in a write heavy workload large shared_buffers causes
> checkpoints to have huge IO, but since you are not making changes in
> shared_buffers this will not happen.
Yes, good idea.
> * You can also increase checkpoint_timeout to a very large value to
> prevent checkpoints, since you don't need them. WAL level can be
> minimal as well.
Already set to 5 min with 50 segments and 0.9 completion target (but
used also for the bulk loading). But of course I will set it to 1 hour
when in read only mode.
> * You can also run a CLUSTER command on one of your indexes to group
> data that is frequently accessed together into the same segment of
> disk so you can get more of it in a single IO operation.
Hum... I was planning to put indexes and data on different disks (SSD) /
controller to maximize bandwith use, am I wrong?
> * You can also run the VACUUM FULL command during off-hours to get
> your tables vacuumed and statistics up-to-date. It's usually too
> much overhead to be worthwhile but since you are not doing updates
> you only have to do it once then don't need to worry about
> autovacuum being aggressive enough.
Vacuum is done at the end of the import and then set to off.
> * I don't think that removing locks will provide any benefit if your
> queries are truly read-only since ordinary read-only transactions do
> not require any locks
At least a read write lock should be needed, but you're right: better
take a look at the source code to be sure.
Best regards
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