query a table with lots of coulmns

Hi mailing list,

I am relatively new to postgres. I have a table with 500 coulmns and
about 40 mio rows. I call this cache table where one column is a unique
key (indexed) and the 499 columns (type integer) are some values
belonging to this key.

Now I have a second (temporary) table (only 2 columns one is the key of
my cache table) and I want do an inner join between my temporary table
and the large cache table and export all matching rows. I found out,
that the performance increases when I limit the join to lots of small parts.
But it seems that the databases needs a lot of disk io to gather all 499
data columns.
Is there a possibilty to tell the databases that all these colums are
always treated as tuples and I always want to get the whole row? Perhaps
the disk oraganization could then be optimized?

Thank you for feedback and ideas
Best
Neo