org.apache.derby.catalog.types
Class StatisticsImpl

java.lang.Object
  org.apache.derby.catalog.types.StatisticsImpl

All Implemented Interfaces:

java.io.Externalizable, java.io.Serializable, Statistics, Formatable, TypedFormat

public class StatisticsImpl
extends java.lang.Object
implements Statistics, Formatable

See Also:

Serialized Form

Field Summary

private long	numRows
private long	numUnique

Constructor Summary

StatisticsImpl()
Zero argument constructor for Formatable Interface

StatisticsImpl(long numRows, long numUnique)
Constructor for StatisticsImpl.

Method Summary

long	getRowEstimate() Returns the estimated number of rows in the index.
int	getTypeFormatId() Get a universally unique identifier for the type of this object.
void	readExternal(java.io.ObjectInput in)
double	selectivity(java.lang.Object[] predicates)
java.lang.String	toString()
void	writeExternal(java.io.ObjectOutput out) Write this object to a stream of stored objects.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

numRows

private long numRows

numUnique

private long numUnique

Constructor Detail

StatisticsImpl

public StatisticsImpl(long numRows,
                      long numUnique)

Constructor for StatisticsImpl.

Parameters:

numRows - number of rows in the conglomerate for which this statistic is being created.

numUnique - number of unique values in the key for which this statistic is being created.

StatisticsImpl

public StatisticsImpl()

Zero argument constructor for Formatable Interface

Method Detail

getRowEstimate

public long getRowEstimate()

Returns the estimated number of rows in the index.

Specified by:

getRowEstimate in interface Statistics

Returns:

Number of rows.

selectivity

public double selectivity(java.lang.Object[] predicates)

Specified by:

selectivity in interface Statistics

Returns:

the selectivity for a set of predicates.

See Also:

Statistics.selectivity(java.lang.Object[])

readExternal

public void readExternal(java.io.ObjectInput in)
                  throws java.io.IOException,
                         java.lang.ClassNotFoundException

Specified by:

readExternal in interface java.io.Externalizable

Throws:

java.io.IOException

java.lang.ClassNotFoundException

See Also:

Externalizable.readExternal(java.io.ObjectInput)

writeExternal

public void writeExternal(java.io.ObjectOutput out)
                   throws java.io.IOException

Write this object to a stream of stored objects.

Specified by:

writeExternal in interface java.io.Externalizable

Parameters:

out - write bytes here.

Throws:

java.io.IOException - thrown on error

getTypeFormatId

public int getTypeFormatId()

Description copied from interface: TypedFormat

Get a universally unique identifier for the type of this object.

Specified by:

getTypeFormatId in interface TypedFormat

Returns:

the format id which corresponds to this class.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

See Also:

Object.toString()