Update materialized view when urderlying tables change

Question

I have a materialized view defined this way:

CREATE MATERIALIZED VIEW M_FOO
REFRESH COMPLETE ON COMMIT
AS
    SELECT FOO_ID, BAR
    FROM FOO
    WHERE BAR IS NO         


        

Answer 1

A fast refresh will only insert/update/delete changed data into the materialized view. A complete refresh will empty the materialized view and then copy over all rows.

The "on commit" means the materialized view will be refreshed whenever a change is committed in the master table. So your current syntax is going to be extremely inefficient. Every time somebody changes any row in foo, m_foo will be truncated and then every row in foo table will be inserted.

You can do better with fast refreshes, where only the modified rows in foo will be sent to m_foo. That gives you consistency without lots of overhead.

create materialized view log on foo with primary key; -- assuming you have a primary key, you should create materialized view m_foo refresh fast on commit as \;

There are some additional subtleties with grants and synonyms if you're using db links, or the schema that owns foo isn't the one that owns m_foo.