Caching by Postgres

Hi all,

I like to know the caching policies of Postgresql.
What parameter in the postgresql.conf affects the
cache size used by the Postgresql? As far as I have
searched my knowledge of the parameters are

1. shared_buffers - Sets the limit on the amount of
shared memory used. If I take this is as the cache
size then my performance should increase with the
increase in the size of shared_buffers. But it seems
it is not the case and my performance actually
decreases with the increase in the shared_buffers. I
have a RAM size of 32 GB. The table which I use more
frequently has around 68 million rows. Can I cache
this entire table in RAM?

2. work_mem - It is the amount of memory used by an
operation. My guess is once the operation is complete
this is freed and hence has nothing to do with the
caching.

3. effective_cache_size - The parameter used by the
query planner and has nothing to do with the actual
caching.

So kindly help me in pointing me to the correct
parameter to set.

It will be great if you can point me to the docs that
explains the implementation of caching in Postgresql
which will help me in understanding things much
clearly.

Thanks in advance.
Gokul.

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