Oracle : Creating record-column history - oracle

Question

Usually the best solution to capture history would be to create a trigger which takes snapshot of the record while updating into a history table however :
1.) My table contains 60 columns but I want to capture history for only 10 of them.
2.) The data from source come's with a Submit date which is not captured in the target table. The history need's to be captured based on that Submit date sent by the source and not based on current sysdate.
3.) We have control over the Select, Update process.
Proposed Solution:
We created a function as below
In(Primary Key, Submit_Date, Column_Name, Old Value, New Value)
PRAGMA AUTONOMOUS_TRANSACTION;
Fetch max(Submit_date) From History using PK;
If max_Submit_date is Null:
Insert in History using PK, 01-01-1700 as Submit date, Column Name, Old_Value;
Insert into History using PK & Submit_date & new Value;
Elsif max_Submit_date = Submit_date
Update History using PK & Submit_date with new Value;
Elsif max_Submit_date < Submit_date
Insert into History using PK & Submit_date & new Value;
End if;
commit;
While selecting data for update we added
select .... ,
DECODE(T.Column_VALUE_1,S.Column_VALUE_1,NULL,Function(PK,'COLUMN_NAME_1', S.Submit_Date, T.Column_VALUE_1, S.Column_VALUE_1)) XYZ,
DECODE(T.Column_VALUE_2,S.Column_VALUE_2,NULL,Function(PK,'COLUMN_NAME_2', S.Submit_Date, T.Column_VALUE_2, S.Column_VALUE_2)) XYZ,
From Source_Table S Join Target Table T Where ...
I can see that the solution is not ideal or efficient. Please advise if the requirement can be met in any other way.

Answer 1

One solution could be to perform it for all records, at once, utilizing a MERGE INTO statement. Since your submit_date is part of insert and also comparison, ideal solution to avoid conflict would be to have a version column in your History table, containing 1 for initial version and 2,3,4.. and so on for subsequent versions.
And instead of comparing with decode and calling function, you could exclude all such records in where clause condition.
MERGE INTO HISTORY h USING
(
with m(pk,max_Submit_date) AS
( select pk,submit_date,version
FROM HISTORY o where
version IN ( select MAX(version) max_version
FROM HISTORY i where i.pk = o.pk ) ,
select .... PK,
CASE WHEN m.max_Submit_date is Null
THEN 01-01-1700
WHEN m.max_Submit_date <= s.Submit_date THEN
s.Submit_date
END as Submit_date,
decode( m.max_Submit_date,NULL,T.Column_VALUE_1, S.Column_VALUE_1)
decode( m.max_Submit_date,NULL,T.Column_VALUE_2, S.Column_VALUE_2)
..
CASE WHEN m.max_Submit_date is Null
THEN 1
WHEN m.max_Submit_date <= s.Submit_date
THEN m.max_version + 1 new_version
ELSE
m.max_version
END version
From Source_Table S Join Target Table T
JOIN m ON m.pk = s.pk
Where ..
( T.Column_VALUE_1 != S.Column_VALUE_1 ) OR
( T.Column_VALUE_2 != S.Column_VALUE_2 ) OR
..
..
) cur
ON ( cur.pk = h.pk and h.version = cur.version )
WHEN MATCHED THEN
Update SET h.Submit_date = cur.Submit_date,
h.Column_VALUE_1 = s.Column_VALUE_1,
h.Column_VALUE_2 = s.Column_VALUE_2
..
WHEN NOT MATCHED THEN INSERT
INSERT (PK,submit_date,column_1,..) VALUES (..);