postgres autoincrement not updated on explicit id inserts

Question

I have the following table in postgres:

CREATE TABLE \"test\" (
    \"id\" serial NOT NULL PRIMARY KEY,
    \"value\" text
)

I am doing fol

Answer 1

It can be done automatically using a trigger. This way you are sure that the largest value is always used as the next default value.

CREATE OR REPLACE FUNCTION set_serial_id_seq()
RETURNS trigger AS
$BODY$
  BEGIN
   EXECUTE (FORMAT('SELECT setval(''%s_%s_seq'', (SELECT MAX(%s) from %s));',
   TG_TABLE_NAME,
   TG_ARGV[0],
   TG_ARGV[0],
   TG_TABLE_NAME));
    RETURN OLD;
   END;
$BODY$
LANGUAGE plpgsql;  

CREATE TRIGGER set_mytable_id_seq
AFTER INSERT OR UPDATE OR DELETE
ON mytable
FOR EACH STATEMENT
  EXECUTE PROCEDURE  set_serial_id_seq('mytable_id');

The function can be reused for multiple tables. Change "mytable" to the table of interest.

For more info regarding triggers:

https://www.postgresql.org/docs/9.1/plpgsql-trigger.html

https://www.postgresql.org/docs/9.1/sql-createtrigger.html