http://www.postgresql.org/docs/8.1/static/indexes-multicolumn.html An index can be defined on more than one column of a table. For example, if you have a table of this form: CREATE TABLE test2 ( major int, minor int, name varchar ); (say, you keep your /dev directory in a database...) and you frequently make queries like SELECT name FROM test2 WHERE major = constant AND minor = constant; then it may be appropriate to define an index on the columns major and minor together, e.g., CREATE INDEX test2_mm_idx ON test2 (major, minor);
