On 12/9/2010 6:25 AM, Paul Taylor wrote:
Hi, Im using Postgres 8.3 on a Macbook Pro Labtop.
I using the database with just one db connection to build a lucene
search index from some of the data, and Im trying to improve
performance. The key thing is that I'm only a single user but
manipulating large amounts of data , i.e processing tables with upto 10
million rows in them, so I think want to configure Postgres so that it
can create large temporary tables in memory
I've tried changes various parameters such as shared_buffers, work_mem
and checkpoint_segments but I don't really understand what they values
are, and the documentation seems to be aimed towards configuring for
multiple users, and my changes make things worse. For example my machine
has 2GB of memory and I read if using as a dedicated server you should
set shared memory to 40% of total memory, but when I increase to more
than 30MB Postgres will not start complaining about my SHMMAX limit.
Paul
You need to bump up your SHMMAX is your OS. I'm sure google knows how
to do it. (in linux use sysctl, so it may be similar in macos).
checkpoint_segments: I've bumped them up to 10, but only when inserting
a huge amount of data, not sure how much it'll help otherwise.
shared_buffers: this is the big one. Set it big, 1G maybe
work_mem: this is for temp work a query might need to do, like sorting,
merging, etc. A big value (100Meg or so) would be ok. Its Per User,
but since there is only one of you, splurge.
There is also an effective_cache_size (or something like that): its the
amount of memory PG can assume is being used for disk cache. Its not
something that'll be allocated. So you have 2G, 1G for PG, 300Meg for
os and other stuff, so 700Meg for effective_cache_size?
In Linux I use "free" to see how much is being used for disk cache, and
set it to that.
-Andy
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