deletion of records before commit doesn't work

I've come up with this example and I want to know why it does what it
does.

-- snip --
You are now connected to database template1.
CREATE DATABASE
You are now connected to database testing.
psql:test2.sql:11: NOTICE:  CREATE TABLE/UNIQUE will create implicit
index 'subdivs_name_key' for table 'subdivs'
psql:test2.sql:11: NOTICE:  CREATE TABLE/PRIMARY KEY will create
implicit index 'subdivs_pkey' for table 'subdivs'
CREATE
psql:test2.sql:20: NOTICE:  CREATE TABLE will create implicit sequence
'blah_id_seq' for SERIAL column 'blah.id'
psql:test2.sql:20: NOTICE:  CREATE TABLE/PRIMARY KEY will create
implicit index 'blah_pkey' for table 'blah'
psql:test2.sql:20: NOTICE:  CREATE TABLE will create implicit
trigger(s) for FOREIGN KEY check(s)
CREATE
INSERT 218198 1
BEGIN
INSERT 218199 1
psql:test2.sql:29: ERROR:  triggered data change violation on relation
"blah"
ROLLBACK
BEGIN
INSERT 218200 1
UPDATE 1
DELETE 1
ROLLBACK
-- snip --

and the test file is attached.

--
hackers ally