Methods, systems and program products for query optimization using sideways information passing. In one implementation, a join clause in a query is identified that specifies an outer table of tuples to be joined with an inner table, the outer table having one or more attributes, and each of the attributes of the outer table having values stored in an attribute file that is distinct from attribute files in which the values of other attributes are stored. A plan for the query is created which, when executed, causes selection of a subset of tuples of the outer table to serve as input to the join clause in place of the outer table based on one or more predicates applied to the inner table.