Configuration - PostgreSQL 9 Administration - page 62

For example on Linux, add the following line to /etc/sysctl.conf :
kernel.shmmax=value
Don't worry about setting effective_cache_size . It is much less important a parameter
than you might think; no need for too much fuss selecting the value.
If you're doing heavy write activity, then you may want to set wal_buffers to a much higher
value than the default.
If you're doing heavy write activity and/or large data loads, you then may want to set
checkpoint_segments higher than the default.
If your database has many large queries, you may wish to set work_mem to a value higher
than the default.
Make sure autovacuum is turned on, unless you have a very good reason to turn it off. Most
people don't. Please see later chapters for more information on autovacuum.
To simplify some of this, I recommend that you refer to the following URL:
http://pgfoundry.org/projects/pgtune/
Leave the settings at that for now. Don't fuss too much about getting the exact settings right.
You can change most of them later, so you can take an iterative approach to improving things.
Get the basics right, and keep it simple and solid. Then buy Greg Smith's topic
on PostgreSQL performance
Especially, don't touch fsync parameter. It's keeping you safe.
Adding an external module to PostgreSQL
Another one of PostgreSQL's strengths is its extensibility. Extensibility was one of the original
design goals, stretching back to the late 1980s. Now, in PostgreSQL 9.0, there are many
additional modules that plug into the core PostgreSQL server.
There are many kinds of additional module offerings, such as the following:
F additional functions
F additional datatypes
F additional operators
F additional indexes