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

java.lang.Object
  org.apache.derby.impl.services.daemon.IndexStatisticsDaemonImpl.KeyComparator

Enclosing class:

IndexStatisticsDaemonImpl

private static class IndexStatisticsDaemonImpl.KeyComparator
extends java.lang.Object

Support class used to compare keys when scanning indexes.

Field Summary

private DataValueDescriptor[]	curr
private static int	FETCH_SIZE Number of rows fetched per iteration.
private DataValueDescriptor[]	lastUniqueKey
private long	numRows
private DataValueDescriptor[]	prev
private DataValueDescriptor[][]	rowBufferArray
private int	rowsReadLastRead

Constructor Summary

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

Method Summary

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 java.lang.Object

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

Field Detail

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 Detail

IndexStatisticsDaemonImpl.KeyComparator

public IndexStatisticsDaemonImpl.KeyComparator(ExecIndexRow ir)

Creates a key comparator for the given index.

Parameters:

ir - index row (template)

Method Detail

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.