Software Architect's Handbook

Having too many indexes

There is a cost associated with adding an index to a table, so when it comes to indexes, you can have too much of a good thing. Every time that a record is added or updated in a table, an index record also has to be added or updated, incurring some additional overhead to those transactions. In terms of storage, indexes take up additional disk space, increasing the overall size of your database.

The more indexes you have on a table, the more the query optimizer of the database management system (DBMS) will have to take into consideration for a particular query. The query optimizer is a component of the DBMS that analyzes queries to determine the most efficient execution plans for them.

For example, the query optimizer ...