org.apache.derby.impl.sql.execute
Class ScrollInsensitiveResultSet

java.lang.Object
  org.apache.derby.impl.sql.execute.BasicNoPutResultSetImpl
      org.apache.derby.impl.sql.execute.NoPutResultSetImpl
          org.apache.derby.impl.sql.execute.ScrollInsensitiveResultSet

All Implemented Interfaces:

CursorResultSet, NoPutResultSet, ResultSet, RowLocationRetRowSource, RowSource

public class ScrollInsensitiveResultSet
extends NoPutResultSetImpl
implements CursorResultSet

Provide insensitive scrolling functionality for the underlying result set. We build a disk backed hash table of rows as the user scrolls forward, with the position as the key. For read-only result sets the hash table will containg the following columns:

  +-------------------------------+
  | KEY                           |
  +-------------------------------+
  | Row                           |
  +-------------------------------+

where key is the position of the row in the result set and row is the data. And for updatable result sets it will contain:

  +-------------------------------+
  | KEY                           | [0]
  +-------------------------------+
  | RowLocation                   | [POS_ROWLOCATION]
  +-------------------------------+
  | Deleted                       | [POS_ROWDELETED]
  +-------------------------------+
  | Updated                       | [POS_ROWUPDATED]
  +-------------------------------+
  | Row                           | [extraColumns ... n]
  +-------------------------------+

where key is the position of the row in the result set, rowLocation is the row location of that row in the Heap, Deleted indicates whether the row has been deleted, Updated indicates whether the row has been updated, and row is the data.

Field Summary

private boolean	afterLast
private boolean	beforeFirst
private int	currentPosition
private int	extraColumns
private BackingStoreHashtable	ht
private boolean	keepAfterCommit
private static int	LAST_EXTRA_COLUMN
private int	lastPosition
private long	maxRows
private boolean	needsRepositioning
int	numFromHashTable
int	numToHashTable
private static int	POS_ROWDELETED
private static int	POS_ROWLOCATION
private static int	POS_ROWUPDATED
private SQLInteger	positionInHashTable
private int	positionInSource
private ExecRow	resultRow
private boolean	seenFirst
private boolean	seenLast
NoPutResultSet	source
private int	sourceRowWidth
private CursorResultSet	target

Fields inherited from class org.apache.derby.impl.sql.execute.NoPutResultSetImpl

checkNullCols, clonedExecRow, cncLen, resultSetNumber, targetResultSet

Fields inherited from class org.apache.derby.impl.sql.execute.BasicNoPutResultSetImpl

activation, beginTime, closeTime, compactRow, constructorTime, currentRow, endExecutionTime, finished, isOpen, isTopResultSet, nextTime, numOpens, openTime, optimizerEstimatedCost, optimizerEstimatedRowCount, resultDescription, rowsFiltered, rowsSeen, startExecutionTime, subqueryTrackingArray

Fields inherited from interface org.apache.derby.iapi.sql.ResultSet

CURRENT_RESULTSET_ONLY, ENTIRE_RESULTSET_TREE, ISAFTERLAST, ISBEFOREFIRST, ISFIRST, ISLAST

Fields inherited from interface org.apache.derby.iapi.sql.execute.NoPutResultSet

ABSOLUTE, FIRST, LAST, NEXT, PREVIOUS, RELATIVE

Constructor Summary

ScrollInsensitiveResultSet(NoPutResultSet source, Activation activation, int resultSetNumber, int sourceRowWidth, double optimizerEstimatedRowCount, double optimizerEstimatedCost)
Constructor for a ScrollInsensitiveResultSet

Method Summary

private void	addRowToHashTable(ExecRow sourceRow, int position, RowLocation rowLoc, boolean rowUpdated) Add a row to the backing hash table, keyed on position.
boolean	checkRowPosition(int isType) Determine if the cursor is before the first row in the result set.
void	close() If the result set has been opened, close the open scan.
void	finish() Tells the system that there will be no more access to any database information via this result set; in particular, no more calls to open().
ExecRow	getAbsoluteRow(int row) Returns the row at the absolute position from the query, and returns NULL when there is no such position.
ExecRow	getCurrentRow() Gets information from last getNextRow call.
ExecRow	getFirstRow() Returns the first row from the query, and returns NULL when there are no rows.
ExecRow	getLastRow() Returns the last row from the query, and returns NULL when there are no rows.
ExecRow	getNextRowCore() Return the requested values computed from the next row (if any) for which the restriction evaluates to true.
private ExecRow	getNextRowFromSource()
ExecRow	getPreviousRow() Returns the previous row from the query, and returns NULL when there are no more previous rows.
ExecRow	getRelativeRow(int row) Returns the row at the relative position from the current cursor position, and returns NULL when there is no such position.
private DataValueDescriptor[]	getRowArrayFromHashTable(int position) Get the row data at the specified position from the hash table.
private ExecRow	getRowFromHashTable(int position) Get the row at the specified position from the hash table.
RowLocation	getRowLocation() Gets information from its source.
int	getRowNumber() Returns the row number of the current row.
long	getTimeSpent(int type) Return the total amount of time spent in this ResultSet
boolean	isDeleted() Returns TRUE if the row was been deleted within the transaction, otherwise returns FALSE
boolean	isForUpdate() Is this ResultSet or it's source result set for update This method will be overriden in the inherited Classes if it is true
boolean	isUpdated() Returns TRUE if the row was been updated within the transaction, otherwise returns FALSE
void	markRowAsDeleted() Marks the resultSet's currentRow as deleted after a delete has been issued by either by using positioned delete or JDBC's deleteRow method.
void	openCore() open a scan on the source. scan parameters are evaluated at each open, so there is probably some way of altering their values...
private void	positionInLastFetchedRow() Positions the cursor in the last fetched row.
void	reopenCore() reopen a scan on the table. scan parameters are evaluated at each open, so there is probably some way of altering their values...
ExecRow	setAfterLastRow() Sets the current position to after the last row and returns NULL because there is no current row.
ExecRow	setBeforeFirstRow() Sets the current position to before the first row and returns NULL because there is no current row.
void	updateRow(ExecRow row, RowChanger rowChanger) Updates the resultSet's current row with it's new values after an update has been issued either using positioned update or JDBC's udpateRow method.

Methods inherited from class org.apache.derby.impl.sql.execute.NoPutResultSetImpl

clearCurrentRow, clearOrderableCache, closeRowSource, getCursorName, getNextRowFromRowSource, getResultDescription, getValidColumns, needsRowLocation, needsToClone, positionScanAtRowLocation, printQualifiers, resultSetNumber, rowLocation, setCurrentRow, setNeedsRowLocation, setTargetResultSet, skipRow, skipScan

Methods inherited from class org.apache.derby.impl.sql.execute.BasicNoPutResultSetImpl

addWarning, attachStatementContext, checkCancellationFlag, cleanUp, dumpTimeStats, finishAndRTS, getActivation, getAutoGeneratedKeysResultset, getBeginExecutionTimestamp, getCompactRow, getCurrentTimeMillis, getElapsedMillis, getEndExecutionTimestamp, getEstimatedRowCount, getExecuteTime, getExecutionFactory, getLanguageConnectionContext, getNextRow, getPointOfAttachment, getScanIsolationLevel, getSubqueryTrackingArray, getTransactionController, getWarnings, isClosed, markAsTopResultSet, modifiedRowCount, open, recordConstructorTime, requiresRelocking, returnsRows, setCompactRow, setCompatRow

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.sql.ResultSet

addWarning, cleanUp, clearCurrentRow, getActivation, getAutoGeneratedKeysResultset, getBeginExecutionTimestamp, getCursorName, getEndExecutionTimestamp, getExecuteTime, getNextRow, getResultDescription, getSubqueryTrackingArray, getWarnings, isClosed, modifiedRowCount, open, returnsRows

Field Detail

source

public NoPutResultSet source

sourceRowWidth

private int sourceRowWidth

ht

private BackingStoreHashtable ht

resultRow

private ExecRow resultRow

positionInSource

private int positionInSource

currentPosition

private int currentPosition

lastPosition

private int lastPosition

seenFirst

private boolean seenFirst

seenLast

private boolean seenLast

beforeFirst

private boolean beforeFirst

afterLast

private boolean afterLast

numFromHashTable

public int numFromHashTable

numToHashTable

public int numToHashTable

maxRows

private long maxRows

keepAfterCommit

private boolean keepAfterCommit

extraColumns

private int extraColumns

positionInHashTable

private SQLInteger positionInHashTable

target

private CursorResultSet target

needsRepositioning

private boolean needsRepositioning

POS_ROWLOCATION

private static final int POS_ROWLOCATION

See Also:

Constant Field Values

POS_ROWDELETED

private static final int POS_ROWDELETED

See Also:

Constant Field Values

POS_ROWUPDATED

private static final int POS_ROWUPDATED

See Also:

Constant Field Values

LAST_EXTRA_COLUMN

private static final int LAST_EXTRA_COLUMN

See Also:

Constant Field Values

Constructor Detail

ScrollInsensitiveResultSet

public ScrollInsensitiveResultSet(NoPutResultSet source,
                                  Activation activation,
                                  int resultSetNumber,
                                  int sourceRowWidth,
                                  double optimizerEstimatedRowCount,
                                  double optimizerEstimatedCost)
                           throws StandardException

Constructor for a ScrollInsensitiveResultSet

Parameters:

source - The NoPutResultSet from which to get rows to scroll through

activation - The activation for this execution

resultSetNumber - The resultSetNumber

sourceRowWidth - # of columns in the source row

Throws:

StandardException - on error

Method Detail

openCore

public void openCore()
              throws StandardException

open a scan on the source. scan parameters are evaluated at each open, so there is probably some way of altering their values...

Specified by:

openCore in interface NoPutResultSet

Throws:

StandardException - thrown on failure

reopenCore

public void reopenCore()
                throws StandardException

reopen a scan on the table. scan parameters are evaluated at each open, so there is probably some way of altering their values...

Specified by:

reopenCore in interface NoPutResultSet

Overrides:

reopenCore in class BasicNoPutResultSetImpl

Throws:

StandardException - thrown if cursor finished.

See Also:

NoPutResultSet.openCore()

getAbsoluteRow

public ExecRow getAbsoluteRow(int row)
                       throws StandardException

Returns the row at the absolute position from the query, and returns NULL when there is no such position. (Negative position means from the end of the result set.) Moving the cursor to an invalid position leaves the cursor positioned either before the first row (negative position) or after the last row (positive position). NOTE: An exception will be thrown on 0.

Specified by:

getAbsoluteRow in interface ResultSet

Overrides:

getAbsoluteRow in class BasicNoPutResultSetImpl

Parameters:

row - The position.

Returns:

The row at the absolute position, or NULL if no such position.

Throws:

StandardException - Thrown on failure

See Also:

Row

getRelativeRow

public ExecRow getRelativeRow(int row)
                       throws StandardException

Returns the row at the relative position from the current cursor position, and returns NULL when there is no such position. (Negative position means toward the beginning of the result set.) Moving the cursor to an invalid position leaves the cursor positioned either before the first row (negative position) or after the last row (positive position). NOTE: 0 is valid. NOTE: An exception is thrown if the cursor is not currently positioned on a row.

Specified by:

getRelativeRow in interface ResultSet

Overrides:

getRelativeRow in class BasicNoPutResultSetImpl

Parameters:

row - The position.

Returns:

The row at the relative position, or NULL if no such position.

Throws:

StandardException - Thrown on failure

See Also:

Row

setBeforeFirstRow

public ExecRow setBeforeFirstRow()

Sets the current position to before the first row and returns NULL because there is no current row.

Specified by:

setBeforeFirstRow in interface ResultSet

Overrides:

setBeforeFirstRow in class BasicNoPutResultSetImpl

Returns:

NULL.

See Also:

Row

getFirstRow

public ExecRow getFirstRow()
                    throws StandardException

Returns the first row from the query, and returns NULL when there are no rows.

Specified by:

getFirstRow in interface ResultSet

Overrides:

getFirstRow in class BasicNoPutResultSetImpl

Returns:

The first row, or NULL if no rows.

Throws:

StandardException - Thrown on failure

See Also:

Row

getNextRowCore

public ExecRow getNextRowCore()
                       throws StandardException

Description copied from interface: NoPutResultSet

Return the requested values computed from the next row (if any) for which the restriction evaluates to true.

restriction and projection parameters are evaluated for each row.

Specified by:

getNextRowCore in interface NoPutResultSet

Specified by:

getNextRowCore in class BasicNoPutResultSetImpl

Returns:

the next row in the result

Throws:

StandardException - thrown on failure

See Also:

NoPutResultSet.getNextRowCore()

getPreviousRow

public ExecRow getPreviousRow()
                       throws StandardException

Returns the previous row from the query, and returns NULL when there are no more previous rows.

Specified by:

getPreviousRow in interface ResultSet

Overrides:

getPreviousRow in class BasicNoPutResultSetImpl

Returns:

The previous row, or NULL if no more previous rows.

Throws:

StandardException - Thrown on failure

See Also:

Row

getLastRow

public ExecRow getLastRow()
                   throws StandardException

Returns the last row from the query, and returns NULL when there are no rows.

Specified by:

getLastRow in interface ResultSet

Overrides:

getLastRow in class BasicNoPutResultSetImpl

Returns:

The last row, or NULL if no rows.

Throws:

StandardException - Thrown on failure

See Also:

Row

setAfterLastRow

public ExecRow setAfterLastRow()
                        throws StandardException

Sets the current position to after the last row and returns NULL because there is no current row.

Specified by:

setAfterLastRow in interface ResultSet

Overrides:

setAfterLastRow in class BasicNoPutResultSetImpl

Returns:

NULL.

Throws:

StandardException - Thrown on failure

See Also:

Row

checkRowPosition

public boolean checkRowPosition(int isType)
                         throws StandardException

Determine if the cursor is before the first row in the result set.

Specified by:

checkRowPosition in interface ResultSet

Overrides:

checkRowPosition in class BasicNoPutResultSetImpl

Returns:

true if before the first row, false otherwise. Returns false when the result set contains no rows.

Throws:

StandardException - Thrown on error.

getRowNumber

public int getRowNumber()

Returns the row number of the current row. Row numbers start from 1 and go to 'n'. Corresponds to row numbering used to position current row in the result set (as per JDBC).

Specified by:

getRowNumber in interface ResultSet

Overrides:

getRowNumber in class BasicNoPutResultSetImpl

Returns:

the row number, or 0 if not on a row

getNextRowFromSource

private ExecRow getNextRowFromSource()
                              throws StandardException

Throws:

StandardException

close

public void close()
           throws StandardException

If the result set has been opened, close the open scan.

Specified by:

close in interface ResultSet

Overrides:

close in class NoPutResultSetImpl

Throws:

StandardException - thrown on error

finish

public void finish()
            throws StandardException

Description copied from interface: ResultSet

Tells the system that there will be no more access to any database information via this result set; in particular, no more calls to open(). Will close the result set if it is not already closed.

Specified by:

finish in interface ResultSet

Overrides:

finish in class BasicNoPutResultSetImpl

Throws:

StandardException - on error

getTimeSpent

public long getTimeSpent(int type)

Return the total amount of time spent in this ResultSet

Specified by:

getTimeSpent in interface ResultSet

Parameters:

type - CURRENT_RESULTSET_ONLY - time spent only in this ResultSet ENTIRE_RESULTSET_TREE - time spent in this ResultSet and below.

Returns:

long The total amount of time spent (in milliseconds).

getRowLocation

public RowLocation getRowLocation()
                           throws StandardException

Gets information from its source. We might want to have this take a CursorResultSet in its constructor some day, instead of doing a cast here?

Specified by:

getRowLocation in interface CursorResultSet

Returns:

the row location of the current cursor row.

Throws:

StandardException - thrown on failure

See Also:

CursorResultSet

getCurrentRow

public ExecRow getCurrentRow()
                      throws StandardException

Gets information from last getNextRow call.

Specified by:

getCurrentRow in interface CursorResultSet

Returns:

the last row returned.

Throws:

StandardException - thrown on failure.

See Also:

CursorResultSet

addRowToHashTable

private void addRowToHashTable(ExecRow sourceRow,
                               int position,
                               RowLocation rowLoc,
                               boolean rowUpdated)
                        throws StandardException

Add a row to the backing hash table, keyed on position. When a row gets updated when using scrollable insensitive updatable result sets, the old entry for the row will be deleted from the hash table and this method will be called to add the new values for the row to the hash table, with the parameter rowUpdated = true so as to mark the row as updated. The latter is done in order to implement detectability of own changes for result sets of this type.

Parameters:

sourceRow - The row to add.

position - The key

rowLoc - The rowLocation of the row to add.

rowUpdated - Indicates whether the row has been updated.

Throws:

StandardException

getRowFromHashTable

private ExecRow getRowFromHashTable(int position)
                             throws StandardException

Get the row at the specified position from the hash table.

Parameters:

position - The specified position.

Returns:

The row at that position.

Throws:

StandardException - thrown on failure

getRowArrayFromHashTable

private DataValueDescriptor[] getRowArrayFromHashTable(int position)
                                                throws StandardException

Get the row data at the specified position from the hash table.

Parameters:

position - The specified position.

Returns:

The row data at that position.

Throws:

StandardException - thrown on failure

positionInLastFetchedRow

private void positionInLastFetchedRow()
                               throws StandardException

Positions the cursor in the last fetched row. This is done before navigating to a row that has not previously been fetched, so that getNextRowCore() will re-start from where it stopped.

Throws:

StandardException

updateRow

public void updateRow(ExecRow row,
                      RowChanger rowChanger)
               throws StandardException

Description copied from interface: NoPutResultSet

Updates the resultSet's current row with it's new values after an update has been issued either using positioned update or JDBC's udpateRow method.

Specified by:

updateRow in interface NoPutResultSet

Overrides:

updateRow in class NoPutResultSetImpl

Parameters:

row - new values for the currentRow

rowChanger - holds information about row: what columns of it is to be used for updating, and what underlying base table column each such column corresponds to.

Throws:

StandardException - thrown on failure.

See Also:

Sets the updated column of the hash table to true and updates the row in the hash table with the new values for the row.

markRowAsDeleted

public void markRowAsDeleted()
                      throws StandardException

Description copied from interface: NoPutResultSet

Marks the resultSet's currentRow as deleted after a delete has been issued by either by using positioned delete or JDBC's deleteRow method.

Specified by:

markRowAsDeleted in interface NoPutResultSet

Overrides:

markRowAsDeleted in class NoPutResultSetImpl

Throws:

StandardException - thrown on failure.

See Also:

Sets the deleted column of the hash table to true in the current row.

isDeleted

public boolean isDeleted()
                  throws StandardException

Returns TRUE if the row was been deleted within the transaction, otherwise returns FALSE

Returns:

True if the row has been deleted, otherwise false

Throws:

StandardException - on error

isUpdated

public boolean isUpdated()
                  throws StandardException

Returns TRUE if the row was been updated within the transaction, otherwise returns FALSE

Returns:

True if the row has been deleted, otherwise false

Throws:

StandardException - on error

isForUpdate

public boolean isForUpdate()

Description copied from class: NoPutResultSetImpl

Is this ResultSet or it's source result set for update This method will be overriden in the inherited Classes if it is true

Specified by:

isForUpdate in interface NoPutResultSet

Overrides:

isForUpdate in class NoPutResultSetImpl

Returns:

Whether or not the result set is for update.