Query Optimizer

The query optimizer formulates a query plan to fetch the data rows that are required to process a query. The optimizer evaluates the different ways in which a query might be performed. For example, the optimizer must determine whether indexes should be used. If the query includes a join, the optimizer must determine the join plan (hash or nested loop) and the order in which tables are evaluated or joined.

For more information on the optimizer, see your IBM Informix Performance Guide.