Oracle: Materialized View not refreshed when using a Prebuilt Table

Question

I'm having problems when using the Prebuilt Table option in a MV in Oracle 12. This code works fine:

CREATE TABLE empt 
  ( ename VARCHAR2(20),
    empno INTEGER PRIMARY KEY);

CREATE MATERIALIZED VIEW LOG ON empt
   WITH SEQUENCE , rowid (empno)
 INCLUDING NEW VALUES;

CREATE MATERIALIZED VIEW empt_MV
    REFRESH FAST ON COMMIT 
    WITH ROWID
     AS
     SELECT count(*) numberofemps
     FROM empt ;

INSERT INTO empt VALUES ('A',1);
COMMIT;

SELECT * FROM empt_MV;

Previous Select return, as expected:

NUMBEROFEMPS
------------
           1

But, if I use the ON PREBUILT TABLE option, nothing happens. I mean, the MV remains empty:

drop materialized view empt_mv;
drop materialized view log on empt;
drop table empt;

CREATE TABLE empt 
  ( ename VARCHAR2(20),
    empno INTEGER PRIMARY KEY);

CREATE MATERIALIZED VIEW LOG ON empt
   WITH SEQUENCE , rowid (empno)
 INCLUDING NEW VALUES;

CREATE TABLE empt_MV (
  numberofemps NUMBER);

CREATE MATERIALIZED VIEW empt_MV
    ON PREBUILT TABLE
    REFRESH FAST ON COMMIT 
    WITH ROWID
     AS
     SELECT count(*) numberofemps
     FROM empt ;

INSERT INTO empt VALUES ('A',1);
COMMIT;

SELECT * FROM empt_MV;

Previous Selects returns no rows.

Anyone knows what happens?

Answer 1

You can't use REFRESH FAST if you are employing WITH ROWID - on your prebuilt table. WITH ROWID Clause

Answer 2

This varies greatly by Oracle version.

Use the instructions provided in the relevant documentation, which will show you how to determine the fast refresh capabilities in your particular situation using DBMS_MView.Explain_MView.

12.1: https://docs.oracle.com/database/121/REPLN/repmview.htm#REPLN304