Detecting and Resolving Index Ownership Issues in Oracle Databases

Index ownership inconsistencies in Oracle databases can lead to performance and maintenance challenges. These issues often arise when indexes are mistakenly created under a schema different from the table’s owner. This blog post provides a set of SQL queries to identify, investigate, and resolve such discrepancies, including how to review the index creation details and drop the incorrectly created indexes.

Step 1: Identify Index Ownership Discrepancies

The first step is to identify cases where an index is created under a schema different from the table owner. The following query fetches the table owner, table name, index owner, and index name for such mismatches:

SET PAGESIZE 50
SET LINESIZE 120
COLUMN table_owner FORMAT A20
COLUMN table_name FORMAT A30
COLUMN index_owner FORMAT A20
COLUMN index_name FORMAT A30

SELECT 
    table_owner, 
    table_name, 
    index_owner, 
    index_name
FROM 
    dba_ind_columns
WHERE 
    table_owner != index_owner;

This query uses the dba_ind_columns view to compare the table’s owner with the index’s owner. The output is formatted for better readability.

Step 2: Retrieve Index Creation Details

Once the mismatched indexes are identified, you can check when the index was created. Use the following query to retrieve all metadata related to the index from the dba_objects view:

SET PAGESIZE 50
SET LINESIZE 120
COLUMN owner FORMAT A20
COLUMN object_name FORMAT A30
COLUMN object_type FORMAT A15
COLUMN created FORMAT A20
COLUMN last_ddl_time FORMAT A20

SELECT 
    owner, 
    object_name, 
    object_type, 
    created, 
    last_ddl_time 
FROM 
    dba_objects
WHERE 
    object_name = 'INDEX_NAME' 
    AND object_type = 'INDEX';

Replace INDEX_NAME with the actual name of the index you are investigating. This query provides details like the index owner, creation time, and last modification time.

Step 3: Drop the Incorrectly Created Index

To resolve the ownership mismatch, drop the index created under the incorrect schema. Use the following command:

DROP INDEX OWNER.INDEX_NAME;

Replace OWNER and INDEX_NAME with the actual schema name and index name, respectively. Be cautious when running this command, as dropping an index can impact query performance.

Step 4: Retrieve the DDL for the Index

Before dropping or recreating an index, you may want to review its definition using the DBMS_METADATA package. The following query retrieves the complete DDL for the index:

SET LONG 9999
SET PAGESIZE 50
SET LINESIZE 120

SELECT 
    DBMS_METADATA.GET_DDL('INDEX', 'INDEX_NAME', 'OWNER') 
FROM 
    DUAL;

Replace INDEX_NAME and OWNER with the index name and its owner. This will output the full definition of the index.

Summary of Steps

1. Identify indexes created under a schema different from the table’s owner using dba_ind_columns.
2. Check the metadata and creation details of the index using dba_objects.
3. Drop the incorrectly created index using the DROP INDEX command.
4. Retrieve the DDL for the index to understand its structure or recreate it under the correct schema.

Best Practices

1. Always validate index ownership during schema reviews or migrations.
2. Use proper roles and permissions to avoid accidental creation of indexes under the wrong schema.
3. Regularly audit your database using queries like the ones above to maintain consistency.

By following the steps outlined in this post, you can effectively detect and resolve index ownership issues in your Oracle database. This ensures better performance and easier maintenance of your database objects.