insert function for postgresql partition tutorial in https://www.if-not-true-then-false.com/2009/howto-create-postgresql-table-partitioning-part-1/

bulk_insert_for_pg_table_partitioning.sql

CREATE OR REPLACE FUNCTION insert_date(INTEGER,INTEGER,DATE) RETURNS VOID AS $$
DECLARE
	mystart alias for $1;
	myend alias for $2;
	mydate alias for $3;
BEGIN
    FOR i IN mystart..myend LOOP
    INSERT INTO impressions_by_day values(i,mydate,round(random()*10000));
    END LOOP;
END;
$$ LANGUAGE 'plpgsql' STRICT;