Expectations of MEM requirements for a DB with large tables.

Hello to all,

I am new to the PostgreSQL world, as well as the Linux world... kind of a
double whammy...

Anyway, I crashed my system the other day when I did a "select *" from one
of my large tables (about 5.5gb in size). Now this is not something that
will normally happen, as I would normally have some criteria to reduce the
output size, but it got me thinking...

Does anyone know what the ratio of data output size (say from a select) to
the amount of
RAM used is?

Hopefully the answer is not 1 to 1... as I would need to buy ALOT of RAM...

Other relevant info, RedHat Linux 2.2.17 kernel, PostgreSQL 7.0.2.

Thank you in advance for any and all help.

Note: I posted this to "Admin" also, but I'm not quite sure if it's really a
"installation" question, so I'm posting it here also.

-Michael Miyabara-McCaskey