org.apache.derby.catalog

public Interface Statistics

Known Direct Implementers: org.apache.derby.catalog.types.StatisticsImpl

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 Derby optimizer to estimate cost and selectivity of different query plans.

Method Summary

Modifier and Type	Method and Description
public long	Returns: Number of rows. getRowEstimate() Returns the estimated number of rows in the index.
public double	Returns: the selectivity for a set of predicates. selectivity(Object[] The predicates to evaluate predicates)

Method Detail

getRowEstimate	back to summary
public long getRowEstimate() Returns the estimated number of rows in the index. Returns:long Number of rows.

getRowEstimate

back to summary

public long getRowEstimate()

Returns the estimated number of rows in the index.

Returns:long: Number of rows.

selectivity	back to summary
public double selectivity(Object[] predicates) Parameters predicates:Object[] The predicates to evaluate Returns:double the selectivity for a set of predicates.