How to check if an index is effective in PL/SQL?

To check if the index is effective, you can use the following method: 1. Use the EXPLAIN PLAN statement: In PL/SQL, you can use the EXPLAIN PLAN statement to check the execution plan of a query. The execution plan will show detailed information about the indexes and other optimization techniques used in the query. By examining the execution plan, you can determine if the index is being used. Here is an example of using the EXPLAIN PLAN statement:

EXPLAIN PLAN FOR SELECT * FROM your_table WHERE your_column = 'your_value';

After executing the above statement, you can access the execution plan by querying the PLAN_TABLE table.

SELECT * FROM PLAN_TABLE;

Search for information related to indexes in the results, such as index names, index types, etc. Use the DBMS_XPLAN.DISPLAY procedure: The DBMS_XPLAN.DISPLAY procedure is a tool for formatting and displaying execution plans. You can use this procedure to check the index information in the execution plan. Here is an example using the DBMS_XPLAN.DISPLAY procedure:

SET SERVEROUTPUT ON;
DECLARE
  plan_table dbms_xplan.table_type;
BEGIN
  dbms_xplan.clear();
  dbms_xplan.display(plan_table, 'PLAN_TABLE', 'ALL');
END;
/

After executing the above code, you can search for information related to indexes in the output, such as index names and types. Another option is to use the V$SQL_PLAN view, which stores the execution plan information of the most recent SQL statements. You can query this view to check if indexes are being used. The following is an example of querying the V$SQL_PLAN view.

SELECT * FROM V$SQL_PLAN WHERE SQL_ID = 'your_sql_id';

You can check whether an index has been used by querying the results. The above are several common methods to check if an index is effective. Depending on the specific situation, choose the appropriate method to see the usage of the index.