I've found an incompatibility between PostgreSQL 8.2.4 and 8.3.0 which is not clearly documented. Here's a short example: CREATE TABLE t1 ( id CHAR(5) NOT NULL, PRIMARY KEY (id) ); INSERT INTO t1 (id) VALUES ('t1id1'); INSERT INTO t1 (id) VALUES ('t1id2'); INSERT INTO t1 (id) VALUES ('t1id3'); CREATE TABLE t2 ( id SERIAL NOT NULL, t1id VARCHAR(5) NOT NULL, PRIMARY KEY (id) ); INSERT INTO t2 (t1id) VALUES ('t1id1'); INSERT INTO t2 (t1id) VALUES ('t1id2'); INSERT INTO t2 (t1id) VALUES ('t1id3'); ALTER TABLE t2 ADD CONSTRAINT t2_t1id_fk FOREIGN KEY (t1id) REFERENCES t1 (id); (Note the different column types.) This works fine in 8.2.4, but 8.3.0 rejects the ALTER TABLE with the following (somewhat misleading) error message: ERROR: insert or update on table "t2" violates foreign key constraint "t2_t1id_fk" DETAIL: Key (t1id)=(t1id1) is not present in table "t1". Should this be documented explicitly? Should the error message look different? ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match