May have posted this earlier...
It would seem that caching the plans for foreign keys has some unwanted
side effects.
test=# select version(); version
------------------------------------------------------------------------PostgreSQL 7.4beta4 on i386-portbld-freebsd4.8,
compiledby GCC 2.95.4
(1 row)
test=#
test=# create table a (col integer primary key);
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "a_pkey"
for table "a"
CREATE TABLE
test=#
test=# create table b (col integer primary key references a on update
cascade on delete cascade);
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "b_pkey"
for table "b"
CREATE TABLE
test=#
test=#
test=# insert into a values (1);
INSERT 687978 1
test=# insert into b values (1);
INSERT 687979 1
test=#
test=# insert into a values (2);
INSERT 687980 1
test=# insert into b values (2);
INSERT 687981 1
test=#
test=# delete from a where col = 1;
DELETE 1
test=#
test=# alter table b drop constraint b_pkey;
ALTER TABLE
test=#
test=# delete from a where col = 2;
ERROR: could not open relation with OID 687972
