Automatically get notified when a database record is updated - oracle

Question

I have an oracle client database with 500k client records. Every month i run a batch process to produce some monthly analytical using the client data. But sometimes, the database owner tells me that they have updated the data and i need to run the batch again.
I would like to build a monitoring /notification service that will immediately tell me when a particular client record got updated and what was the update. That way i know if the update can be ignored or not.
I can of course run an hourly sql query that compares each client record with its previous snapshot but is there a better solution?
Does something like Kafka work in this scenario? How exactly?

Answer 1

You can use Continuous Query Notification (previously known as Database Change Notifications).
Read more about it:
DBMS_CQ_NOTIFICATION with examples
Continuous Query Notification for JDBC
#JustinCave also suggests a pretty good option to create simple trigger and enable it only when you really need it, but probably it would be easier just to create materialized view log and check it periodically for new changes. You can get changed rows from it.
Simple example:
SQL> create table t(id int primary key, a int, b int);
Table created.
SQL> create materialized view log on t with primary key, rowid;
Materialized view log created.
SQL> select log_table from user_mview_logs where master='T';
LOG_TABLE
--------------------------------
MLOG$_T
SQL> desc mlog$_t
Name Null? Type
----------------------------------------- -------- ----------------------------
ID NUMBER
M_ROW$$ VARCHAR2(255)
SNAPTIME$$ DATE
DMLTYPE$$ VARCHAR2(1)
OLD_NEW$$ VARCHAR2(1)
CHANGE_VECTOR$$ RAW(255)
XID$$ NUMBER
SQL> column M_ROW$$ format a20;
SQL> column CHANGE_VECTOR$$ format a10;
SQL> select * from mlog$_t;
no rows selected
SQL> insert into t(id, a, b) values(1,1,1);
1 row created.
SQL> commit;
Commit complete.
SQL> select * from mlog$_t;
ID M_ROW$$ SNAPTIME$$ D O CHANGE_VEC XID$$
---------- -------------------- ------------------- - - ---------- ----------
1 AAASWNAAMAAAAEXAAA 4000-01-01 00:00:00 I N FE 2.8148E+15