CREATE TABLE spec --1
(
    id int NOT NULL PRIMARY KEY,
    table_name varchar NOT NULL,
    column_name varchar NOT NULL,
    max_value int NOT NULL
);

INSERT INTO spec (id,table_name,column_name,max_value) --2
VALUES (1,'spec','id',1);

CREATE OR REPLACE FUNCTION get_next_value_in_column(_table_name varchar, _column_name varchar) --3
    RETURNS int AS
$$
DECLARE
    _max_value int;
BEGIN
    SELECT max_value INTO _max_value
    FROM spec
    WHERE table_name = _table_name AND  column_name = _column_name;

    IF _max_value IS NOT NULL THEN
        UPDATE spec
        SET max_value = _max_value+1
        WHERE table_name = _table_name AND column_name = _column_name;
        RETURN _max_value+1;
    ELSE
        -- find _max_value in table_name on column_name
        EXECUTE format('SELECT MAX(%s) FROM %s',quote_ident(_column_name),quote_ident(_table_name)) INTO _max_value;
        IF _max_value IS NULL THEN
            _max_value = 0;
        END IF;

        INSERT INTO spec(id, table_name, column_name, max_value)
        VALUES (get_next_value_in_column('spec','id'),_table_name,_column_name,_max_value+1);
        RETURN _max_value+1;
    END IF;

END;
$$ LANGUAGE plpgsql;

SELECT get_next_value_in_column('spec','id'); --4

SELECT id, table_name, column_name, max_value
FROM spec; --5

SELECT get_next_value_in_column('spec','id'); -- 6

SELECT id, table_name, column_name, max_value
FROM spec; --7

CREATE  TABLE test --8
(
    id int NOT NULL PRIMARY KEY
);

INSERT INTO test(id) --9
VALUES (10);

SELECT  get_next_value_in_column('test','id'); -- 10

SELECT id, table_name, column_name, max_value
FROM spec; --11

SELECT get_next_value_in_column('test','id'); --12

SELECT id, table_name, column_name, max_value
FROM spec; --13

CREATE TABLE test2 --14
(
    num_value1 int NOT NULL,
    num_value2 int NOT NULL
);

SELECT get_next_value_in_column('test2','num_value1'); --15

SELECT id, table_name, column_name, max_value --16
FROM spec;

SELECT get_next_value_in_column('test2','num_value1'); --17

SELECT id, table_name, column_name, max_value
FROM spec; --18

SELECT get_next_value_in_column('test2','num_value2'); --20

SELECT id, table_name, column_name, max_value
FROM spec;--21

SELECT get_next_value_in_column('test2','num_value1');
SELECT get_next_value_in_column('test2','num_value1');
SELECT get_next_value_in_column('test2','num_value1');
SELECT get_next_value_in_column('test2','num_value1');
SELECT get_next_value_in_column('test2','num_value1'); --22

SELECT id, table_name, column_name, max_value
FROM spec; --23

DROP FUNCTION get_next_value_in_column(_table_name varchar, _column_name varchar); --24

DROP TABLE spec; --25
DROP TABLE test;
DROP TABLE test2;