net.sf.farrago.catalog
Class FarragoTableStatistics

java.lang.Object
  net.sf.farrago.catalog.FarragoTableStatistics

All Implemented Interfaces:

RelStatSource

public class FarragoTableStatistics
extends Object
implements RelStatSource

This class reads statistics for a Farrago table from data stored in the catalog.

Version:

$Id: //open/dev/farrago/src/net/sf/farrago/catalog/FarragoTableStatistics.java#10 $

Author:

John Pham

Field Summary

private Timestamp	labelTimestamp
private FarragoRepos	repos
private FemAbstractColumnSet	table

Constructor Summary

FarragoTableStatistics(FarragoRepos repos, FemAbstractColumnSet table)
Deprecated.

FarragoTableStatistics(FarragoRepos repos, FemAbstractColumnSet table, Timestamp labelTimestamp)
Initialize an object for retrieving table statistics, optionally based on a label setting.

Method Summary

RelStatColumnStatistics	getColumnStatistics(int ordinal, SargIntervalSequence predicate) Returns statistics pertaining to a column specified by the 0-based ordinal and the sargable predicates associated with that column.
Double	getRowCount() Returns the number of rows in a relation, as determined by statistics

Methods inherited from class java.lang.Object

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

Field Detail

repos

private FarragoRepos repos

table

private FemAbstractColumnSet table

labelTimestamp

private Timestamp labelTimestamp

Constructor Detail

FarragoTableStatistics

public FarragoTableStatistics(FarragoRepos repos,
                              FemAbstractColumnSet table)

Deprecated.

Initialize an object for retrieving table statistics

Parameters:

repos - the repository containing stats

table - the table for which to retrieve stats

FarragoTableStatistics

public FarragoTableStatistics(FarragoRepos repos,
                              FemAbstractColumnSet table,
                              Timestamp labelTimestamp)

Initialize an object for retrieving table statistics, optionally based on a label setting.

Parameters:

repos - the repository containing stats

table - the table for which to retrieve stats

labelTimestamp - the creation timestamp of the label that determines which stats to retrieve; null if there is no label setting

Method Detail

getRowCount

public Double getRowCount()

Description copied from interface: RelStatSource

Returns the number of rows in a relation, as determined by statistics

Specified by:

getRowCount in interface RelStatSource

Returns:

a row count, or null if one could not be determined

getColumnStatistics

public RelStatColumnStatistics getColumnStatistics(int ordinal,
                                                   SargIntervalSequence predicate)

Description copied from interface: RelStatSource

Returns statistics pertaining to a column specified by the 0-based ordinal and the sargable predicates associated with that column. The second argument can be null if there are no sargable predicates on the column.

Specified by:

getColumnStatistics in interface RelStatSource

Parameters:

ordinal - zero based column ordinal

predicate - associated predicates(s), evaluated as intervals

Returns:

filtered column statistics, or null if they could not be obtained