Class IndexStatisticsDaemonImpl.KeyComparator

java.lang.Object

org.apache.derby.impl.services.daemon.IndexStatisticsDaemonImpl.KeyComparator

Enclosing class:

IndexStatisticsDaemonImpl

private static class IndexStatisticsDaemonImpl.KeyComparator
extends Object

Support class used to compare keys when scanning indexes.

Field Summary

Fields

Modifier and Type	Field	Description
private DataValueDescriptor[]	curr
private static final int	FETCH_SIZE	Number of rows fetched per iteration.
private DataValueDescriptor[]	lastUniqueKey
private long	numRows
private DataValueDescriptor[]	prev
private final DataValueDescriptor[][]	rowBufferArray
private int	rowsReadLastRead

Constructor Summary

Constructors

Constructor	Description
KeyComparator(ExecIndexRow ir)	Creates a key comparator for the given index.

Method Summary

Modifier and Type	Method	Description
int	compareWithPrevKey(int index)	Compares the key at the specified index with the previous key.
int	fetchRows(GroupFetchScanController gsc)	Fetches rows from the scan controller.
long	getRowCount()	Returns the number of rows fetched.

Methods inherited from class Object

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

Field Details

FETCH_SIZE

private static final int FETCH_SIZE

Number of rows fetched per iteration.

See Also:

• Constant Field Values

rowBufferArray

private final DataValueDescriptor[][] rowBufferArray

lastUniqueKey

private DataValueDescriptor[] lastUniqueKey

curr

private DataValueDescriptor[] curr

prev

private DataValueDescriptor[] prev

rowsReadLastRead

private int rowsReadLastRead

numRows

private long numRows

Constructor Details

KeyComparator

public KeyComparator(ExecIndexRow ir)

Creates a key comparator for the given index.

Parameters:

ir - index row (template)

Method Details

fetchRows

public int fetchRows(GroupFetchScanController gsc)
              throws StandardException

Fetches rows from the scan controller.

Parameters:

gsc - the scan controller

Returns:

Number of rows fetched.

Throws:

StandardException - if fetching rows fails

compareWithPrevKey

public int compareWithPrevKey(int index)
                       throws StandardException

Compares the key at the specified index with the previous key.

Parameters:

index - row index

Returns:

-1 if the current and previous key are identical, the index of the changed part of the key otherwise ([0, key length>)

Throws:

StandardException - if comparing the two keys fails

getRowCount

public long getRowCount()

Returns the number of rows fetched.

Returns:

Number of rows fetched.