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

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

All Implemented Interfaces:

ScanControllerRowSource, ScanManager, GenericScanController, GroupFetchScanController, RowCountable, RowLocationRetRowSource, RowSource, ScanController, ScanInfo

public class SortBufferRowSource
extends Scan
implements ScanControllerRowSource

Wrapping the output of a SortBuffer in a RowSource for the benefit of the createAndLoadConglomerate and loadConglomerate interface. Scan implements ScanController, this class just implements the RowSource interface.

Field Summary

private int	maxFreeListSize
(package private) SortBuffer	sortBuffer The Sort buffer where rows come from
private SortObserver	sortObserver
protected TransactionManager	tran The TransactionManager that opened this scan.
private boolean	writingToDisk

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

GE, GT, NA

Constructor Summary

SortBufferRowSource(SortBuffer sortBuffer, TransactionManager tran, SortObserver sortObserver, boolean writingToDisk, int maxFreeListSize)

Method Summary

void	close() Close the scan
boolean	closeForEndTransaction(boolean closeHeldScan) Close the scan
void	closeRowSource() Close the rowSource
void	fetch(DataValueDescriptor[] result) Fetch the row at the current position of the Scan.
boolean	fetchNext(DataValueDescriptor[] row) Fetch the (partial) row at the next position of the Scan.
void	fetchWithoutQualify(DataValueDescriptor[] result) Fetch the row at the current position of the Scan and does not apply the qualifiers.
DataValueDescriptor[]	getNextRowFromRowSource() Get the next row as an array of column objects.
FormatableBitSet	getValidColumns() All columns are always set from a sorter
boolean	needsRowLocation() needsRowLocation returns true iff this the row source expects the drainer of the row source to call rowLocation after getting a row from getNextRowFromRowSource.
boolean	needsToClone() Does the caller of getNextRowFromRowSource() need to clone the row in order to keep a reference to the row past the getNextRowFromRowSource() call which returned the row.
boolean	next() Move to the next position in the scan.
void	rowLocation(RowLocation rl) rowLocation is a callback for the drainer of the row source to return the rowLocation of the current row, i.e, the row that is being returned by getNextRowFromRowSource.

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

delete, didNotQualify, doesCurrentPositionQualify, fetchLocation, fetchNextGroup, fetchNextGroup, fetchSet, getAllScanInfo, getEstimatedRowCount, getScanInfo, isCurrentPositionDeleted, isHeldAfterCommit, isKeyed, isTableLocked, newRowLocationTemplate, positionAtRowLocation, reopenScan, reopenScanByRowLocation, replace, 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.ScanController

delete, didNotQualify, doesCurrentPositionQualify, fetchLocation, isCurrentPositionDeleted, isHeldAfterCommit, positionAtRowLocation, replace

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

getScanInfo, isKeyed, isTableLocked, newRowLocationTemplate, reopenScan, reopenScanByRowLocation

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

getEstimatedRowCount, setEstimatedRowCount

Field Detail

sortBuffer

SortBuffer sortBuffer

The Sort buffer where rows come from

tran

protected TransactionManager tran

The TransactionManager that opened this scan.

maxFreeListSize

private int maxFreeListSize

writingToDisk

private boolean writingToDisk

sortObserver

private SortObserver sortObserver

Constructor Detail

SortBufferRowSource

SortBufferRowSource(SortBuffer sortBuffer,
                    TransactionManager tran,
                    SortObserver sortObserver,
                    boolean writingToDisk,
                    int maxFreeListSize)

Method Detail

getNextRowFromRowSource

public DataValueDescriptor[] getNextRowFromRowSource()

Description copied from interface: RowSource

Get the next row as an array of column objects. The column objects can be a JBMS Storable or any Serializable/Externalizable/Formattable/Streaming type.
A return of null indicates that the complete set of rows has been read.

A null column can be specified by leaving the object null, or indicated by returning a non-null getValidColumns. On streaming columns, it can be indicated by returning a non-null get FieldStates.

If RowSource.needToClone() is true then the returned row (the DataValueDescriptor[]) is guaranteed not to be modified by drainer of the RowSource (except that the input stream will be read, of course) and drainer will keep no reference to it before making the subsequent nextRow call. So it is safe to return the same DataValueDescriptor[] in subsequent nextRow calls if that is desirable for performance reasons.

If RowSource.needToClone() is false then the returned row (the DataValueDescriptor[]) may be be modified by drainer of the RowSource, and the drainer may keep a reference to it after making the subsequent nextRow call. In this case the client should severe all references to the row after returning it from getNextRowFromRowSource().

Specified by:

getNextRowFromRowSource in interface RowSource

needsRowLocation

public boolean needsRowLocation()

Description copied from interface: RowLocationRetRowSource

needsRowLocation returns true iff this the row source expects the drainer of the row source to call rowLocation after getting a row from getNextRowFromRowSource.

Specified by:

needsRowLocation in interface RowLocationRetRowSource

Returns:

true iff this row source expects some row location to be returned

See Also:

RowLocationRetRowSource.rowLocation(org.apache.derby.iapi.types.RowLocation)

needsToClone

public boolean needsToClone()

Description copied from interface: RowSource

Does the caller of getNextRowFromRowSource() need to clone the row in order to keep a reference to the row past the getNextRowFromRowSource() call which returned the row. This call must always return the same for all rows in a RowSource (ie. the caller will call this once per scan from a RowSource and assume the behavior is true for all rows in the RowSource).

Specified by:

needsToClone in interface RowSource

See Also:

RowSource.needsToClone()

rowLocation

public void rowLocation(RowLocation rl)

Description copied from interface: RowLocationRetRowSource

rowLocation is a callback for the drainer of the row source to return the rowLocation of the current row, i.e, the row that is being returned by getNextRowFromRowSource. This interface is for the purpose of loading a base table with index. In that case, the indices can be built at the same time the base table is laid down once the row location of the base row is known. This is an example pseudo code on how this call is expected to be used:

                boolean needsRL = rowSource.needsRowLocation();
                DataValueDescriptor[] row;
                while((row = rowSource.getNextRowFromRowSource()) != null)
                {
                        RowLocation rl = heapConglomerate.insertRow(row);
                        if (needsRL)
                                rowSource.rowLocation(rl);
                }
                

NeedsRowLocation and rowLocation will ONLY be called by a drainer of the row source which CAN return a row location. Drainer of row source which cannot return rowLocation will guarentee to not call either callbacks. Conversely, if NeedsRowLocation is called and it returns true, then for every row return by getNextRowFromRowSource, a rowLocation callback must also be issued with the row location of the row. Implementor of both the source and the drain of the row source must be aware of this protocol.
The RowLocation object is own by the caller of rowLocation, in other words, the drainer of the RowSource. This is so that we don't need to new a row location for every row. If the Row Source wants to keep the row location, it needs to clone it (RowLocation is a ClonableObject).

Specified by:

rowLocation in interface RowLocationRetRowSource

getValidColumns

public FormatableBitSet getValidColumns()

All columns are always set from a sorter

Specified by:

getValidColumns in interface RowSource

close

public void close()

Close the scan

Specified by:

close in interface GenericScanController

closeForEndTransaction

public boolean closeForEndTransaction(boolean closeHeldScan)

Close the scan

Specified by:

closeForEndTransaction in interface ScanManager

Parameters:

closeHeldScan - If true, means to close scan even if it has been opened to be kept opened across commit. This is used to close these scans on abort.

Returns:

boolean indicating that the close has resulted in a real close of the scan. A held scan will return false if called by closeForEndTransaction(false), otherwise it will return true. A non-held scan will always return true.

closeRowSource

public void closeRowSource()

Close the rowSource

Specified by:

closeRowSource in interface RowSource

next

public boolean next()
             throws StandardException

Description copied from interface: ScanController

Move to the next position in the scan. If this is the first call to next(), the position is set to the first row. Returns false if there is not a next row to move to. It is possible, but not guaranteed, that this method could return true again, after returning false, if some other operation in the same transaction appended a row to the underlying conglomerate.

Specified by:

next in interface GroupFetchScanController

Specified by:

next in interface ScanController

Returns:

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

Throws:

StandardException - Standard exception policy.

fetchWithoutQualify

public void fetchWithoutQualify(DataValueDescriptor[] result)
                         throws StandardException

Fetch the row at the current position of the Scan and does not apply the qualifiers. This method will always throw an exception. (SQLState.SORT_IMPROPER_SCAN_METHOD)

Specified by:

fetchWithoutQualify in interface ScanController

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.fetchWithoutQualify(org.apache.derby.iapi.types.DataValueDescriptor[])

fetch

public void fetch(DataValueDescriptor[] result)
           throws StandardException

Fetch the row at the current position of the Scan.

Specified by:

fetch in interface ScanController

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[])

fetchNext

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

Description copied from interface: ScanController

Fetch the (partial) row at the next position of the Scan. If there is a valid next position in the scan then the value in the destRow storable row is replaced with the value of the row at the current scan position. The columns of the destRow row must be of the same type as the actual columns in the underlying conglomerate. The resulting contents of destRow 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.

Specified by:

fetchNext in interface ScanController

Parameters:

row - The destRow 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