The benefits of join indexes vary considerably among the types of joins used and between simple and aggregate types. The following bulleted list summarizes the conclusions to be drawn from the performance analyses performed.
- All queries that require join processing benefit from join indexes.
- In all tests performed, aggregate join indexes strongly outperform simple join indexes, both with respect to their performance and with respect to their maintenance burden. Queries using an aggregate join index frequently run hundreds of times faster than the same queries against the same tables when no join index is defined.
- The benefits of simple join indexes are typically more modest. Queries using a simple join index typically run from 1.3 to 4.9 times faster than the same queries against the same tables when no join index is defined.
- In-place join indexes handily outperform any join indexes that redistribute rows.