Materialized view data doesn't update - oracle

Question

I want to create a materialized view with fast refresh. The view aggregates values from a single table:
CREATE TABLE N_INSP_DTSEDIF_PLANTAS (
IMPORTACION_ID NUMBER(*,0) NOT NULL,
ID NUMBER(10) NOT NULL,
INSPECCION_ID NUMBER(10) NOT NULL,
NOMBRE_PLANTA VARCHAR2(255 CHAR),
NUM_VIVIENDAS NUMBER(10),
SUP_CONSTRUIDA_VIVIENDAS DECIMAL(10,4),
-- Plus some other columns I don't need
CONSTRAINT N_INSP_DTSEDIF_PLANTAS_P PRIMARY KEY (
IMPORTACION_ID,
ID
) ENABLE,
CONSTRAINT N_INSP_DTSEDIF_PLANTAS_F FOREIGN KEY (IMPORTACION_ID)
REFERENCES IMPORTACION (IMPORTACION_ID)
ON DELETE CASCADE
ENABLE
);
CREATE INDEX N_INSP_DTSEDIF_PLANTAS_X ON N_INSP_DTSEDIF_PLANTAS (IMPORTACION_ID);
CREATE SEQUENCE N_INSP_DTSEDIF_PLANTAS_S
INCREMENT BY 1
START WITH 1
MINVALUE 1
CACHE 20;
CREATE OR REPLACE TRIGGER N_INSP_DTSEDIF_PLANTAS_T
BEFORE INSERT
ON N_INSP_DTSEDIF_PLANTAS
REFERENCING NEW AS NEW OLD AS OLD
FOR EACH ROW
BEGIN
IF :NEW.ID IS NULL THEN
SELECT N_INSP_DTSEDIF_PLANTAS_S.NEXTVAL INTO :NEW.ID FROM DUAL;
END IF;
END N_INSP_DTSEDIF_PLANTAS_T;
/
ALTER TRIGGER N_INSP_DTSEDIF_PLANTAS_T ENABLE;
I've composed this through trial and error:
CREATE MATERIALIZED VIEW LOG ON N_INSP_DTSEDIF_PLANTAS
WITH ROWID, SEQUENCE (IMPORTACION_ID, INSPECCION_ID, NUM_VIVIENDAS, SUP_CONSTRUIDA_VIVIENDAS)
INCLUDING NEW VALUES;
CREATE MATERIALIZED VIEW V_PLANTAS
REFRESH FAST
AS
SELECT IMPORTACION_ID, INSPECCION_ID,
SUM(NUM_VIVIENDAS) AS NUM_VIVIENDAS, SUM(SUP_CONSTRUIDA_VIVIENDAS) AS SUP_CONSTRUIDA_VIVIENDAS
FROM N_INSP_DTSEDIF_PLANTAS
GROUP BY IMPORTACION_ID, INSPECCION_ID;
Objects get created without errors and SELECT * FROM V_PLANTAS returns data. However, the view is stalled. New rows added to N_INSP_DTSEDIF_PLANTAS don't show up at V_PLANTAS.
What did I misunderstand from the documentation?

Answer 1

In the mess of random changes that follow panic and despair I inadvertently dropped the ON COMMIT clause:
CREATE MATERIALIZED VIEW V_PLANTAS
REFRESH FAST ON COMMIT
AS
-- ...
The log itself is also invalid for fast refresh because I also omitted the PRIMARY KEY clause. It should be like:
CREATE MATERIALIZED VIEW LOG ON N_INSP_DTSEDIF_PLANTAS
WITH ROWID, PRIMARY KEY, SEQUENCE (INSPECCION_ID, NUM_VIVIENDAS, SUP_CONSTRUIDA_VIVIENDAS)
INCLUDING NEW VALUES;
(Said that, it's worth noting that materialized tables are not just a simple results cache but a fairly large and complex feature that requires careful planning and maintenance. In many situations is easier to just optimize the underlying query.)