org.apache.derby.catalog
Interface Statistics

All Known Implementing Classes:
StatisticsImpl

public interface Statistics

This interface is used in the column SYS.SYSSTATISTICS.STATISTICS. It encapsulates information collected by the UPDATE STATISTICS command and is used internally by the Cloudscape optimizer to estimate cost and selectivity of different query plans.


Method Summary
 double selectivity(java.lang.Object[] predicates)
           
 

Method Detail

selectivity

public double selectivity(java.lang.Object[] predicates)
Returns:
the selectivity for a set of predicates.


Apache Derby V10.0 Engine Documentation - Copyright © 1997,2004 The Apache Software Foundation or its licensors, as applicable.