double insert on inherited table with where constraint based on sequence - Mailing list pgsql-bugs

Perhaps I'm missing something here, but it looks like I'm getting an
insert into both the parent and child tables when my RULE's where
clause is based on a DEFAULT generated from a sequence. It looks like
nextval on the sequence is called 3 times for every insert.

I don't know if this is properly a bug or just un-expected behaviour.
It seems very counter-intuitive since the rule says DO INSTEAD so ISTM
that either one or the other insert should happen.

ahammond=# \d t2
                         Table "public.t2"
 Column |  Type   |                    Modifiers
--------+---------+-------------------------------------------------
 id     | integer | not null default nextval('t2_id_seq'::regclass)
 name   | text    | not null
Indexes:
    "t2_pkey" PRIMARY KEY, btree (id)
    "t2_name_key" UNIQUE, btree (name)
    "t2_test" btree ((name::integer)) WHERE is_number(name)
Rules:
    t2_part AS
    ON INSERT TO t2
   WHERE new.id > 10 DO INSTEAD  INSERT INTO t2_child (id, name)
  VALUES (new.id, new.name)

ahammond=# SELECT * FROM t2;
 id | name
----+-------
  1 | one
  2 | two
  3 | three
  4 | 4
  5 | 5
(5 rows)

ahammond=# CREATE TABLE t2_child (CHECK (id > 10)) INHERITS (t2);
CREATE TABLE

ahammond=# CREATE RULE t2_part AS ON INSERT TO t2 WHERE id > 10 DO
INSTEAD INSERT INTO t2_child VALUES (NEW.id, NEW.name);
CREATE RULE

ahammond=# INSERT INTO t2 (name) VALUES ('six');
INSERT 0 1
ahammond=# INSERT INTO t2 (name) VALUES ('seven');
INSERT 0 1
ahammond=# INSERT INTO t2 (name) VALUES ('eight');
INSERT 0 0
ahammond=# INSERT INTO t2 (name) VALUES ('9');
INSERT 0 0
ahammond=# INSERT INTO t2 (name) VALUES ('ten');
INSERT 0 0
ahammond=# INSERT INTO t2 (name) VALUES ('11');
INSERT 0 0
ahammond=# INSERT INTO t2 (name) VALUES ('12');
INSERT 0 0
ahammond=# SELECT * FROM t2;
 id | name
----+-------
  1 | one
  2 | two
  3 | three
  4 | 4
  5 | 5
  7 | six
 10 | seven
 12 | seven                     ?
 15 | eight
 18 | 9
 21 | ten
 24 | 11
 27 | 12
(13 rows)

ahammond=# SELECT * FROM ONLY t2 ;
 id | name
----+-------
  1 | one
  2 | two
  3 | three
  4 | 4
  5 | 5
  7 | six
 10 | seven
(7 rows)

ahammond=# SELECT * FROM t2_child ;
 id | name
----+-------
 12 | seven
 15 | eight
 18 | 9
 21 | ten
 24 | 11
 27 | 12
(6 rows)

Note that the "seven" entry appears twice.

Drew