SELECT * FROM t where p or q; - Mailing list pgsql-sql

hi,
on a +10 millions rec table, a simple select:

SELECT * FROM tab where num = x;

time: 5 secondes

SELECT * FROM tab where num = y;

time: 5 secondes


SELECT * FROM tab WHERE num = x OR num = y;

time: more than 10 mn !!!

num is an integer.