Query doesn't update all rows - sql

Question

There's quite big table, more than 10 000 000 rows. It has columns OBJ_ID, DATE_OF_CHANGE, USER. And I added a new column, RECORD_ID, it is empty for now.
I need to update it so RECORD_ID should have numeric values ascending for OBJ_ID and DATE_OF_CHANGE.
I came up with this:
CREATE SEQUENCE REC_ID_SEQ
START WITH 1
INCREMENT BY 1
CACHE 100;
/
CREATE OR REPLACE TRIGGER TRG_REC_ID_SEQ
BEFORE INSERT ON T_HISTORY
FOR EACH ROW
BEGIN
:NEW.RECORD_ID := REC_ID_SEQ.NEXTVAL;
END;
/
DECLARE
O_ID NUMBER := 0;
S_DATE DATE := SYSDATE;
HIST_NUM NUMBER := 0;
LOOP_COUNT NUMBER := 0;
BEGIN
FOR O IN (SELECT ROWID ROW_ID, D.* FROM T_HISTORY D ORDER BY D.OBJ_ID, D.DATE_OF_CHANGE)
LOOP
LOOP_COUNT := LOOP_COUNT + 1;
IF O.OBJ_ID != O_ID OR O.DATE_OF_CHANGE!= S_DATE
THEN
HIST_NUM := HIST_NUM + 1;
END IF;
UPDATE T_HISTORY T SET T.RECORD_ID = HIST_NUM WHERE T.ROWID = O.ROW_ID;
O_ID := O.OBJ_ID;
S_DATE := O.DATE_OF_CHANGE;
IF LOOP_COUNT > 100000 THEN
COMMIT; LOOP_COUNT := 0;
END IF;
END LOOP;
END;
/
But when the command stops working (no errors) I see that about half of rows were not updated. How do I do this the right way?

Answer 1

Use MERGE command and rowid pseudocolumn as a substitute of primary key:
merge into T_HISTORY t
using (
select rownum as xx, t.*
from (
select t.*, rowid as x_rowid
from T_HISTORY t
order by OBJ_ID, DATE_OF_CHANGE
) t
) xx
on (xx.x_rowid = t.rowid )
when matched then update
set t.RECORD_ID = xx;
Live demo: http://sqlfiddle.com/#!4/aad05/2

Answer 2

Similar to #krokodilko's solution, using analytical function:
MERGE INTO t_history t
USING (SELECT obj_id,
date_of_change,
ROW_NUMBER () OVER (ORDER BY obj_id, date_of_change) rn
FROM t_history) r
ON (t.obj_id = r.obj_id AND t.date_of_change = r.date_of_change)
WHEN MATCHED
THEN
UPDATE SET t.record_id = r.rn;