>>>>> "Ivan" == Ivan Voras <ivoras@xxxxxxxxx> writes: Ivan> Hello, Ivan> There's a "users" table with the following structure: Ivan> CREATE TABLE "user" ( Ivan> id SERIAL PRIMARY KEY, Ivan> -- other fields Ivan> ); Ivan> and there's a "friends" table with the following structure: Ivan> CREATE TABLE friend ( Ivan> user1_id INTEGER NOT NULL REFERENCES "user"(id), Ivan> user2_id INTEGER NOT NULL REFERENCES "user"(id), Ivan> -- other fields Ivan> CHECK (user1_id < user2_id), Ivan> PRIMARY KEY (user1_id, user2_id) Ivan> ); Ivan> And I'm running this query: Ivan> SELECT user1_id,user2_id FROM friend WHERE user1_id=42 OR user2_id=42; To get friends of user 42: SELECT user1_id FROM friend WHERE user2_id=42 UNION ALL SELECT user2_id FROM friend WHERE user1_id=42; assuming you create the (user2_id,user1_id) index, this should get you an Append of two index-only scans. We can use UNION ALL here rather than UNION because the table constraints ensure there are no duplicates. -- Andrew (irc:RhodiumToad)
