Indexes play an important role in data warehouse performance, as they do in any relational database. Every dimension table must be indexed on its primary key. Indexes on other columns such as those that identify levels in the hierarchical structure can also be useful in the performance of some specialized queries.
The fact table must be indexed on the composite primary key made up of the foreign keys of the dimension tables.
These are the primary indexes needed for most data warehouse applications because of the simplicity of star and snowflake schemas. Special query and reporting requirements may indicate the need for additional indexes.