Problems with a PostgreSQL upsert query - sql

Question

I'm trying to update the database by either updating or inserting a new record into the vote_user_table. The table is defined as follows:
Column | Type | Modifiers
-----------+---------+--------------------------------------------------------------
id | integer | not null default nextval('vote_user_table_id_seq'::regclass)
review_id | integer | not null
user_id | integer | not null
positive | boolean | default false
negative | boolean | default false
Indexes:
"vote_user_table_pkey" PRIMARY KEY, btree (id)
Here's the query I'm using. I'm actually using parameters for all of the values, but for testing purposes I replaced them with values that I'm sure should work. The username aaa#aaa.com exists.
WITH updated AS (
UPDATE vote_user_table
SET
positive = 'true',
negative = 'false'
FROM usuario
WHERE
review_id = 6 AND
user_id = usuario.id AND
usuario.username ILIKE 'aaa#aaa.com'
RETURNING vote_user_table.id
)
INSERT INTO vote_user_table
(review_id, user_id, positive, negative)
SELECT 6, usuario.id, 'true', 'false'
FROM usuario, updated
WHERE
updated.id IS NULL AND
usuario.username ILIKE 'aaa#aaa.com'
The output I obtain after running the query is:
INSERT 0 0
Although it is supposed to insert the new value, because the row doesn't exist on the database yet. When I inserted a row manually, using only the insert clause, and then performed the upsert query shown above, it updated the row correctly.
I'm using PostgreSQL version 9.2.4.
I got the idea of writing this query from this other question:
Insert, on duplicate update in PostgreSQL?
Any ideas on what could I be doing wrong?
Any suggestion on how can I achieve what I want to do?
Create statement for vote_user_table:
CREATE TABLE vote_user_table (
id integer NOT NULL,
review_id integer NOT NULL,
user_id integer NOT NULL,
positive boolean DEFAULT false,
negative boolean DEFAULT false
);
CREATE SEQUENCE vote_user_table_id_seq
START WITH 1
INCREMENT BY 1
NO MINVALUE
NO MAXVALUE
CACHE 1;
ALTER SEQUENCE vote_user_table_id_seq OWNED BY vote_user_table.id;

Answer 1

The UPDATE in the first CTE updated produces no row. That means, you don't get a NULL value for updated.id either. When joining to updated, you get nothing, so no INSERT happens either.
Should work with NOT EXISTS:
WITH updated AS (
UPDATE vote_user_table v
SET positive = TRUE -- use booleann values ..
,negative = FALSE -- .. instead of quoted string literals
FROM usuario u
WHERE v.review_id = 6 -- guessing origin
AND v.user_id = u.id
AND u.username ILIKE 'aaa#aaa.com'
RETURNING v.id
)
INSERT INTO vote_user_table (review_id, user_id, positive, negative)
SELECT 6, u.id, TRUE, FALSE
FROM usuario u
WHERE NOT EXISTS (SELECT 1 FROM updated)
AND u.username ILIKE 'aaa#aaa.com';
Be aware that there is still a very tiny chance for a race condition under heavy concurrent load. Details under this related question:
Upsert with a transaction