Materialized view log update question

Question

Hi, I am running into a question regarding mview - not sure if it should behave that way or I didn't use it right.
I have two base tables, sales and customers (drived from nested materialized view example in oracle doc):
CREATE TABLE sales
cust_ID VARCHAR2(32 BYTE) NOT NULL,
amount_sold NUMBER,
TEMP VARCHAR2(100 BYTE),
CONSTRAINT sales_pk PRIMARY KEY (cust_id)
CREATE TABLE customers
cust_ID VARCHAR2(32 BYTE) NOT NULL,
CUST_LAST_NAME VARCHAR2(100 BYTE),
TEMP VARCHAR2(100 BYTE),
CONSTRAINT cust_pk PRIMARY KEY (cust_id)
CREATE MATERIALIZED VIEW LOG ON sales
WITH ROWID (cust_id, amount_sold);
CREATE MATERIALIZED VIEW LOG ON customers
WITH ROWID (cust_id, cust_last_name);
Then I create a fast refresh materialized view based on them:
CREATE MATERIALIZED VIEW join_sales_cust
REFRESH FAST ON DEMAND AS
SELECT c.cust_id, c.cust_last_name, s.amount_sold, s.rowid srid, c.rowid crid
FROM sales s, customers c
WHERE s.cust_id = c.cust_id;
Since this materialized view only invole cust_id and amount_sold from sales and cust_id and last_name from customers table, I do not want to trigger materialized view log entry if the TEMP column value gets updated. So follow update shouldn't trigger mlog:
update sales set TEMP='TEMP2' where cust_id=1
but this update should:
update sales set amount_sold=3 where cust_id=1
What I am seeing happenning is any update on the base table will triger mlog entried regardless whether the column is involed in the materialized view or not.
Can someone please confirm if this is the correct behavior and whether there is a way to accomplish what I wanted to do?
Thank you!
Edited by: user3933488 on Jan 8, 2010 12:53 PM

Answer 1

You created the materialized view logs with some columns, which is not necessary when creating a join MV on top of them. You can happily skip those in your MV log definition. And then it becomes clear that those columns are not involved in the decision whether a MV log needs to be updated or not. Everything that happens to the base table gets recorded. The "WITH ROWID" and "INCLUDING NEW VALUES" and the column list only specify WHAT should be recorded when something changed.
Regards,
Rob.