Very long "or" where clause - Mailing list pgsql-general

Hi,
from a table with 100,000,000 rows I have to sum some records using a
query like:

select sum(field1) from mytab where
  (time = 1 and id = 3)
or
  (time = 3 and id = 1)
or
  (time = 2 and id = 5)
[...]


The "or clauses" can be even 10,000,000...
Which would be the best method to access data? Should I use a procedure
on the server side?