ORA-12054: cannot set the ON COMMIT refresh attribute for the materialized view

The ORA-12054: cannot set the ON COMMIT refresh attribute for the materialized view error occurs when you try to create a materialized view with the ON COMMIT refresh option but the conditions necessary for this type of refresh are not met. Here are the common reasons and how to address them:

Common Reasons for ORA-12054 Error

1. Lack of Primary Key or Unique Index on the Base Table:

   • The base table of the materialized view must have a primary key or a unique index for the ON COMMIT refresh option.

2. Complex Queries:

   • The query used to define the materialized view is too complex. It may include joins, subqueries, or other features that prevent the use of ON COMMIT.

3. Unsupported Operations:

   • The materialized view query may contain unsupported operations for ON COMMIT refresh, such as certain aggregate functions or distinct clauses.

Solutions

1. Ensure Primary Key or Unique Index on the Base Table:

• Make sure that the base table has a primary key or at least one unique index.
• CREATE TABLE base_table ( id NUMBER PRIMARY KEY, column1 VARCHAR2(100), column2 DATE );

2. Simplify the Query:

   • Simplify the query to ensure it can be refreshed ON COMMIT.

3. Change to ON DEMAND Refresh:

   • If the above conditions cannot be met, consider changing the refresh method to ON DEMAND.

Example of Creating a Materialized View with ON COMMIT Refresh

Here's an example that ensures the base table has a primary key:

-- Ensure the base table has a primary key CREATE TABLE employees ( emp_id NUMBER PRIMARY KEY, emp_name VARCHAR2(100), emp_salary NUMBER ); -- Create the materialized view with ON COMMIT refresh CREATE MATERIALIZED VIEW emp_mv REFRESH FAST ON COMMIT AS SELECT emp_id, emp_name, emp_salary FROM employees;

Steps to Create Materialized View with Proper Setup

1. Create Base Table with Primary Key:

CREATE TABLE employees (

    emp_id NUMBER PRIMARY KEY,

    emp_name VARCHAR2(100),

    emp_salary NUMBER

);





Create Materialized View Log:


CREATE MATERIALIZED VIEW LOG ON employees
WITH PRIMARY KEY
INCLUDING NEW VALUES;

Create the Materialized View:

CREATE MATERIALIZED VIEW emp_mv REFRESH FAST ON COMMIT AS SELECT emp_id, emp_name, emp_salary FROM employees;

Changing to ON DEMAND Refresh

If the query is too complex or if you cannot ensure a primary key, change the refresh method to ON DEMAND:

CREATE MATERIALIZED VIEW emp_mv REFRESH FAST ON DEMAND AS SELECT emp_id, emp_name, emp_salary FROM employees;

Verify and Troubleshoot

• Verify Primary Key:

SELECT index_name, column_name FROM user_ind_columns WHERE table_name = 'EMPLOYEES';

Check Materialized View Capabilities:

SELECT * FROM user_mview_joins WHERE mview_name = 'EMP_MV';

Following these steps should help you address the ORA-12054 error and successfully create a materialized view with the desired refresh method.