PostgreSQL: Auto-increment based on multi-column unique constraint

Question

One of my tables has the following definition:

CREATE TABLE incidents
(
  id serial NOT NULL,
  report integer NOT NULL,
  year integer NOT NULL,
  month int         


        

Answer 1

I think this will help: http://www.varlena.com/GeneralBits/130.php

Note that in MySQL it is for MyISAM tables only.

PP I have tested advisory locks and found them useless for more than 1 transaction in same time. I am using 2 windows of pgAdmin. First is as simple as possible:

BEGIN;
INSERT INTO animals (grp,name) VALUES ('mammal','dog');
COMMIT;

BEGIN;
INSERT INTO animals (grp,name) VALUES ('mammal','cat');
COMMIT;

ERROR: duplicate key violates unique constraint "animals_pkey"

Second:

BEGIN;
INSERT INTO animals (grp,name) VALUES ('mammal','dog');
INSERT INTO animals (grp,name) VALUES ('mammal','cat');
COMMIT;

ERROR: deadlock detected
SQL state: 40P01
Detail: Process 3764 waits for ExclusiveLock on advisory lock [46462,46496,2,2]; blocked by process 2712.
Process 2712 waits for ShareLock on transaction 136759; blocked by process 3764.
Context: SQL statement "SELECT  pg_advisory_lock( $1 ,  $2 )"
PL/pgSQL function "animals_id_auto" line 15 at perform

And database is locked and can not be unlocked - it is unknown what to unlock.