PostgreSQL SERIAL vs MySQL AUTO_INCREMENT?

Question

I have this MySQL snippet:

CREATE TABLE seq_test (
  id INT PRIMARY KEY AUTO_INCREMENT,
  name TEXT
);

INSERT INTO seq_test(id, name) VALUES (1, 'one');
INSERT INTO seq_test(name) VALUES ('two');

When I try to write this to PostgreSQL:

CREATE TABLE seq_test (
  id SERIAL PRIMARY KEY,
  name TEXT
);

INSERT INTO seq_test(id, name) VALUES (1, 'one');
INSERT INTO seq_test(name) VALUES ('two');

I get the following error:

[23505] ERROR: duplicate key value violates unique constraint "seq_test_pkey"
  Detail: Key (id)=(1) already exists.

This is because in PostgreSQL, inserting one does not increase the identifier for the next insert. How to create a table to match MySQL behavior?

This, of course, is an artificial example, but I am moving a large code base from MySQL to PostgreSQL, and parts of the code (which I do not control) use both styles (i.e. with and without ids), and they work in MySQL, but it does not work in PostgreSQL.

An ugly hack would always do SELECT setval('my_table_id_seq', (SELECT count(*) FROM my_table), TRUE)...

Answer 1

: SERIAL, .

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CREATE OR REPLACE FUNCTION update_seq_val_seq_test()
  RETURNS TRIGGER AS $$
BEGIN
  RAISE NOTICE 'id is %', NEW.id;
  IF NEW.id > currval('seq_test_id_seq' :: REGCLASS)
  THEN
    RAISE NOTICE 'curval is %', currval('seq_test_id_seq' :: REGCLASS);
    PERFORM setval('seq_test_id_seq' :: REGCLASS, (NEW.id) :: BIGINT);
    RAISE NOTICE 'new curval is %', currval('seq_test_id_seq' :: REGCLASS); END IF;
  RETURN NULL;
END;
$$
LANGUAGE 'plpgsql' COST 1;

CREATE TRIGGER seq_test_update_serial
  AFTER INSERT ON seq_test
  FOR EACH ROW EXECUTE PROCEDURE update_seq_val_seq_test();

Fast'n'dirty testing

tests2=# insert into seq_test (name) values ('first');
NOTICE:  id is 30
INSERT 0 1
tests2=# select * from seq_test;
 id | name  
----+-------
 30 | first
(1 row)

tests2=# select currval('seq_test_id_seq'::regclass);
 currval 
---------
      30
(1 row)

tests2=# insert into seq_test (id, name) values (31, 'thirty one');
NOTICE:  id is 31
NOTICE:  curval is 30
NOTICE:  new curval is 31
INSERT 0 1
tests2=# select currval('seq_test_id_seq'::regclass);
 currval 
---------
      31
(1 row)

tests2=# select * from seq_test;
 id |    name    
----+------------
 30 | first
 31 | thirty one
(2 rows)

tests2=# insert into seq_test (name) values ('thirty dunno what');
NOTICE:  id is 32
INSERT 0 1
tests2=# insert into seq_test (id, name) values (21, 'back to the future');
NOTICE:  id is 21
INSERT 0 1
tests2=# select currval('seq_test_id_seq'::regclass);
 currval 
---------
      32
(1 row)

tests2=# select * from seq_test;
 id |        name        
----+--------------------
 30 | first
 31 | thirty one
 32 | thirty dunno what
 21 | back to the future
(4 rows)

tests2=# insert into seq_test (name) values ('thirty dunno what++');
NOTICE:  id is 33
INSERT 0 1
tests2=# select * from seq_test;
 id |        name         
----+---------------------
 30 | first
 31 | thirty one
 32 | thirty dunno what
 21 | back to the future
 33 | thirty dunno what++
(5 rows)

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