This function shows that only clock_timestamp() advances inside a
procedure, not statement_timestamp() or transaction_timestamp():
CREATE OR REPLACE PROCEDURE test_timestamp () AS $$
DECLARE
str TEXT;
BEGIN
WHILE TRUE LOOP
-- clock_timestamp() is updated on every loop
SELECT clock_timestamp() INTO str;
RAISE NOTICE 'clock %', str;
SELECT statement_timestamp() INTO str;
RAISE NOTICE 'statement %', str;
SELECT transaction_timestamp() INTO str;
RAISE NOTICE 'transaction %', str;
COMMIT;
PERFORM pg_sleep(2);
END LOOP;
END
$$ LANGUAGE plpgsql;
CALL test_timestamp();
NOTICE: clock 2018-09-20 19:38:22.575794-04
NOTICE: statement 2018-09-20 19:38:22.575685-04
NOTICE: transaction 2018-09-20 19:38:22.575685-04
--> NOTICE: clock 2018-09-20 19:38:24.578027-04
NOTICE: statement 2018-09-20 19:38:22.575685-04
NOTICE: transaction 2018-09-20 19:38:22.575685-04
This surprised me since I expected a new timestamp after commit. Is
this something we want to change or document? Are there other
per-transaction behaviors we should adjust?
--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ As you are, so once was I. As I am, so you will be. +
+ Ancient Roman grave inscription +
