Join Index Benefits Summary
The benefits of join indexes vary considerably among the various types of joins used
as well as 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; often dramatically,
and sometimes spectacularly.
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.