Inspecting indexes and triggers overhead
In this recipe we will see the overhead introduced by indexes and triggers on DML operations. We will explore alternative ways to implement calculated fields using virtual columns instead of triggers.
How to do it...
The following steps will demonstrate the index and trigger overheads:
- Connect to the
- Create an empty table
MY_CUSTOMERS, copying the
CREATE TABLE MY_CUSTOMERS AS SELECT * FROM CUSTOMERS WHERE ROWNUM < 1;
- Insert all of the records from
MY_CUSTOMERS, measuring time:
SET TIMING ON INSERT INTO MY_CUSTOMERS SELECT * FROM CUSTOMERS; SET TIMING OFF
- Truncate the
TRUNCATE TABLE MY_CUSTOMERS;
- Add a unique index and ...