org.apache.derby.impl.store.access.sort
Class SortScan

java.lang.Object
  org.apache.derby.impl.store.access.sort.Scan
      org.apache.derby.impl.store.access.sort.SortScan

All Implemented Interfaces:

GenericScanController, GroupFetchScanController, RowCountable, ScanController, ScanInfo, ScanManager

Direct Known Subclasses:

MergeScan, SortBufferScan

public abstract class SortScan

extends Scan

Abstract base class for merge sort scans.

Field Summary

protected DataValueDescriptor[]	current The row at the current position of the scan, from which fetch will return values.
protected boolean	hold The row at the current position of the scan, from which fetch will return values.
protected MergeSort	sort The sort that this class is scanning.
protected TransactionManager	tran The transactionManager that opened this scan.

Fields inherited from interface org.apache.derby.iapi.store.access.ScanController

GE, GT, NA

Constructor Summary

(package private)

SortScan(MergeSort sort, TransactionManager tran, boolean hold)

Method Summary

void	close() Close the scan.
void	fetch(DataValueDescriptor[] result) Fetch the row at the current position of the Scan.
boolean	fetchNext(DataValueDescriptor[] row) Fetch the row at the next position of the Scan.

Methods inherited from class org.apache.derby.impl.store.access.sort.Scan

delete, didNotQualify, doesCurrentPositionQualify, fetchLocation, fetchNextGroup, fetchNextGroup, fetchSet, getAllScanInfo, getEstimatedRowCount, getScanInfo, isCurrentPositionDeleted, isKeyed, isTableLocked, newRowLocationTemplate, reopenScan, reopenScanByRowLocation, replace, savePosition, setEstimatedRowCount

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.derby.iapi.store.access.conglomerate.ScanManager

closeForEndTransaction

Methods inherited from interface org.apache.derby.iapi.store.access.ScanController

next

Methods inherited from interface org.apache.derby.iapi.store.access.GroupFetchScanController

next

Field Detail

sort

protected MergeSort sort

The sort that this class is scanning.

tran

protected TransactionManager tran

The transactionManager that opened this scan.

current

protected DataValueDescriptor[] current

The row at the current position of the scan, from which fetch will return values.

hold

protected boolean hold

The row at the current position of the scan, from which fetch will return values.

Constructor Detail

SortScan

SortScan(MergeSort sort,
         TransactionManager tran,
         boolean hold)

Method Detail

fetchNext

public final boolean fetchNext(DataValueDescriptor[] row)
                        throws StandardException

Fetch the row at the next position of the Scan. If there is a valid next position in the scan then the value in the template storable row is replaced with the value of the row at the current scan position. The columns of the template row must be of the same type as the actual columns in the underlying conglomerate. The resulting contents of templateRow after a fetchNext() which returns false is undefined. The result of calling fetchNext(row) is exactly logically equivalent to making a next() call followed by a fetch(row) call. This interface allows implementations to optimize the 2 calls if possible. RESOLVE (mikem - 2/24/98) - come back to this and see if coding this differently saves in sort scans, as did the heap recoding.

Parameters:

row - The template row into which the value of the next position in the scan is to be stored.

Returns:

True if there is a next position in the scan, false if there isn't.

Throws:

StandardException - Standard exception policy.

See Also:

ScanController.fetch(org.apache.derby.iapi.types.DataValueDescriptor[]), RowUtil

fetch

public final void fetch(DataValueDescriptor[] result)
                 throws StandardException

Fetch the row at the current position of the Scan.

Parameters:

result - The row into which the value of the current position in the scan is to be stored.

Throws:

StandardException - Standard exception policy.

See Also:

ScanController.fetch(org.apache.derby.iapi.types.DataValueDescriptor[])

close

public void close()

Close the scan. @see ScanController#close