plpgsql function not inserting data as intended - postgresql

Question

I have the below function compiled successfully. When I do select schema.funtion_name();, the function gets executed but there are no rows inserted in the table schema.table_insert:
CREATE OR REPLACE FUNCTION schema.function_name()
RETURNS void AS
$BODY$
DECLARE cur_1 CURSOR FOR
Select col1 from schema.table1
union
select col1 from schema.table2
union
select col1 from schema.table3
union
select col1 from schema.table4;
BEGIN
FOR rec_i in cur_1 LOOP
insert into schema.table_insert (col1,col2,col3)
select col1,col2,col3
from schema.view
where col1=rec_i.col1
commit;
END LOOP;
END;
$BODY$
LANGUAGE plpgsql STABLE
The select in cursor cur_1 returns more than 900 000 records. When I use the insert statement separately for single record, the record gets inserted in the table.

Answer 1

I have the below function compiled successfully.
No, you haven't.
For starters, plpgsql functions are not "compiled". On creation, only superficial syntax checks are done, then the function body is stored as is. No compilation. Late binding. Nested SQL statements are treated as prepared statements.
That aside, the function you display cannot be created at all. It is syntactical nonsense. Missing semicolon after the INSERT. COMMIT does not make sense and is not allowed in plpgsql. You do not need a cursor for this. Nor looping. Use a simple SQL statement:
INSERT INTO schema.table_insert (col1, col2, col3)
SELECT v.col1, v.col2, v.col3
FROM schema.view v
JOIN (
SELECT col1 FROM schema.table1
UNION
SELECT col1 FROM schema.table2
UNION
SELECT col1 FROM schema.table3
UNION
SELECT col1 FROM schema.table4;
) sub USING (col1);
Equivalent, may be faster:
INSERT INTO schema.table_insert (col1, col2, col3)
SELECT v.col1, v.col2, v.col3
FROM schema.view v
WHERE EXISTS (SELECT 1 schema.table1 WHERE col1 = v.col1)
OR EXISTS (SELECT 1 schema.table2 WHERE col1 = v.col1)
OR EXISTS (SELECT 1 schema.table3 WHERE col1 = v.col1)
OR EXISTS (SELECT 1 schema.table4 WHERE col1 = v.col1);
Can be wrapped up in a function, but plpgsql is overkill. And STABLE, would be wrong for a function containing an INSERT. I suggest a plain SQL function and VOLATILE is the default and correct for this.
CREATE OR REPLACE FUNCTION schema.function_name()
RETURNS void AS
$func$
INSERT ...
$func$ LANGUAGE sql;