9 The TimesTen Query Optimizer
The TimesTen query optimizer is a cost-based optimizer that determines the most efficient way to run a given query by considering possible query plans. The query optimizer uses information about an application's tables and their available indexes to choose a fast path to the data.
A query plan in TimesTen Scaleout is affected by the distribution scheme and the distribution keys of a hash distribution scheme as well as the column and table statistics, the presence or absence of indexes, the volume of data, the number of unique values, and the selectivity of predicates.
Application developers can examine the plan chosen by the optimizer to check that indexes are used appropriately. If necessary, application developers can provide hints to influence the optimizer's behavior so that it considers a different plan.
This chapter includes the following topics: