Materialized view with join

Question

In 10g release 2,I tried to create following materialized view with join:
test_link is a normal table
test_geom is a table contains a column in SDO_GEOMETRY
CREATE MATERIALIZED VIEW LOG ON test_link with rowid
CREATE MATERIALIZED VIEW LOG ON test_geom with rowid,primary key
CREATE MATERIALIZED VIEW MV_LINK USING INDEX REFRESH FAST ON DEMAND AS
SELECT li.rowid link_rowid,geom.rowid geom_rowid,li.link_id,geom.link
FROM test_link li, test_geom geom
WHERE li.link_id=geom.link_id
But I always got an error like:
ORA-12015: cannot create a fast refresh materialized view from a complex query
If I change the geometry table to another table, everything works fine.
Anyone have ideas?

Answer 1

Unfortunately, creating a fast refreshable materialized view on a join with one of the select columns being a user defined type (sdo_geometry is a user defined type) is not allowed. See 5303489 in the metalink bug database.
You could do like the workaround in the article suggests and create two materialized views and then create a regular view on top.
In our scenario, our materialized view also contains unions, so we would really like to have one physical object at the end of the day. One approach that we are currently investigating is to create the materialized view (MV1) without the geometry column, which makes it fast refreshable, and also create a materialized view (MV2) on the table containing the geometry column. MV2 is also fast refreshable. We then create a table (T3) that contains all of the columns from MV1, plus a geometry column. An insert, update, delete trigger on MV1 is created. The trigger is used to push all of the columns from MV1 to T3 and the geometry column from MV2 to T3. I have created the above in one of our test environments and haven't encountered any issues yet.
Let me know if you come up with a better approach.