Problem with commit in function

[Mike Martin]

I have the following function
-- FUNCTION: public.update_log()

-- DROP FUNCTION public.update_log();

CREATE OR REPLACE FUNCTION public.update_log(
)
    RETURNS void
    LANGUAGE 'sql'

    COST 100
    VOLATILE
AS $BODY$

truncate table postgres_log_tmp  ;
COPY postgres_log_tmp FROM '/mnt/pgdata/data/log/postgresql-Mon.csv' WITH
csv;
COPY postgres_log_tmp FROM '/mnt/pgdata/data/log/postgresql-Tue.csv' WITH
csv;
COPY postgres_log_tmp FROM '/mnt/pgdata/data/log/postgresql-Wed.csv' WITH
csv;
COPY postgres_log_tmp FROM '/mnt/pgdata/data/log/postgresql-Thu.csv' WITH
csv;
COPY postgres_log_tmp FROM '/mnt/pgdata/data/log/postgresql-Fri.csv' WITH
csv;
COPY postgres_log_tmp FROM '/mnt/pgdata/data/log/postgresql-Sat.csv' WITH
csv;
COPY postgres_log_tmp FROM '/mnt/pgdata/data/log/postgresql-Sun.csv' WITH
csv;
INSERT INTO postgres_log SELECT * from postgres_log_tmp ON
CONFLICT(session_id, session_line_num) DO NOTHING;
--COMMIT;
truncate table postgres_log_tmp  ;

$BODY$;

ALTER FUNCTION public.update_log()
    OWNER TO postgres;

If I leave the second truncate statement nothing is written to
postgres_log. I assume the insert doesnt finish

Any way to force it to finish before the truncation?