Class OnceResultSet

java.lang.Object

org.apache.derby.impl.sql.execute.BasicNoPutResultSetImpl

org.apache.derby.impl.sql.execute.NoPutResultSetImpl

org.apache.derby.impl.sql.execute.OnceResultSet

All Implemented Interfaces:

NoPutResultSet, ResultSet, RowLocationRetRowSource, RowSource

public class OnceResultSet
extends NoPutResultSetImpl

Takes an expression subquery's result set and verifies that only a single scalar value is being returned. NOTE: A row with a single column containing null will be returned from getNextRow() if the underlying subquery ResultSet is empty.

Nested Class Summary

Nested classes/interfaces inherited from class BasicNoPutResultSetImpl

BasicNoPutResultSetImpl.FieldComparator

Field Summary

Fields

Modifier and Type	Field	Description
private int	cardinalityCheck
static final int	DO_CARDINALITY_CHECK
private GeneratedMethod	emptyRowFun
static final int	NO_CARDINALITY_CHECK
int	pointOfAttachment
private ExecRow	rowWithNulls
NoPutResultSet	source
private StatementContext	statementContext
int	subqueryNumber
static final int	UNIQUE_CARDINALITY_CHECK

Fields inherited from class NoPutResultSetImpl

checkNullCols, clonedExecRow, cncLen, resultSetNumber, targetResultSet

Fields inherited from class 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 NoPutResultSet

ABSOLUTE, FIRST, LAST, NEXT, PREVIOUS, RELATIVE, TEMPORARY_RESULT_SET_NUMBER

Fields inherited from interface ResultSet

CURRENT_RESULTSET_ONLY, ENTIRE_RESULTSET_TREE, ISAFTERLAST, ISBEFOREFIRST, ISFIRST, ISLAST

Constructor Summary

Constructors

Constructor	Description
OnceResultSet(NoPutResultSet s, Activation a, GeneratedMethod emptyRowFun, int cardinalityCheck, int resultSetNumber, int subqueryNumber, int pointOfAttachment, double optimizerEstimatedRowCount, double optimizerEstimatedCost)

Method Summary

Modifier and Type	Method	Description
void	close()	If the result set has been opened, close the open scan.
ExecRow	getNextRowCore()	Return the requested value computed from the next row.
int	getPointOfAttachment()	Return the point of attachment for this subquery.
long	getTimeSpent(int type)	Return the total amount of time spent in this ResultSet
void	openCore()	open a scan on the table. scan parameters are evaluated at each open, so there is probably some way of altering their values...
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...

Methods inherited from class NoPutResultSetImpl

clearCurrentRow, clearOrderableCache, closeRowSource, getCursorName, getNextRowFromRowSource, getResultDescription, getValidColumns, isForUpdate, markRowAsDeleted, needsRowLocation, needsRowLocationForDeferredCheckConstraints, needsToClone, offendingRowLocation, positionScanAtRowLocation, printQualifiers, resultSetNumber, rowLocation, setCurrentRow, setHasDeferrableChecks, setNeedsRowLocation, setTargetResultSet, skipRow, skipScan, unpackHashValue, updateRow

Methods inherited from class BasicNoPutResultSetImpl

addWarning, attachStatementContext, checkCancellationFlag, checkRowPosition, childrenToXML, cleanUp, dumpTimeStats, finish, finishAndRTS, getAbsoluteRow, getActivation, getAutoGeneratedKeysResultset, getBeginExecutionTimestamp, getCompactRow, getCurrentTimeMillis, getElapsedMillis, getEndExecutionTimestamp, getEstimatedRowCount, getExecuteTime, getExecutionFactory, getFirstRow, getLanguageConnectionContext, getLastRow, getNextRow, getPreviousRow, getRelativeRow, getRowNumber, getScanIsolationLevel, getSubqueryTrackingArray, getTransactionController, getWarnings, isClosed, isXplainOnlyMode, markAsTopResultSet, modifiedRowCount, open, recordConstructorTime, requiresRelocking, returnsRows, setAfterLastRow, setBeforeFirstRow, setCompactRow, setCompatRow, toXML, toXML

Methods inherited from class Object

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

Field Details

DO_CARDINALITY_CHECK

public static final int DO_CARDINALITY_CHECK

See Also:

• Constant Field Values

NO_CARDINALITY_CHECK

public static final int NO_CARDINALITY_CHECK

See Also:

• Constant Field Values

UNIQUE_CARDINALITY_CHECK

public static final int UNIQUE_CARDINALITY_CHECK

See Also:

• Constant Field Values

rowWithNulls

private ExecRow rowWithNulls

statementContext

private StatementContext statementContext

source

public NoPutResultSet source

emptyRowFun

private GeneratedMethod emptyRowFun

cardinalityCheck

private int cardinalityCheck

subqueryNumber

public int subqueryNumber

pointOfAttachment

public int pointOfAttachment

Constructor Details

OnceResultSet

public OnceResultSet(NoPutResultSet s,
 Activation a,
 GeneratedMethod emptyRowFun,
 int cardinalityCheck,
 int resultSetNumber,
 int subqueryNumber,
 int pointOfAttachment,
 double optimizerEstimatedRowCount,
 double optimizerEstimatedCost)

Method Details

openCore

public void openCore()
              throws StandardException

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

Throws:

StandardException - thrown if cursor finished.

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()

getNextRowCore

public ExecRow getNextRowCore()
                       throws StandardException

Return the requested value computed from the next 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. StandardException ScalarSubqueryCardinalityViolation Thrown if scalar subquery returns more than 1 row.

See Also:

• NoPutResultSet.getNextRowCore()

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

getPointOfAttachment

public int getPointOfAttachment()

Description copied from interface: NoPutResultSet

Return the point of attachment for this subquery. (Only meaningful for Any and Once ResultSets, which can and will only be at the top of a ResultSet for a subquery.)

Specified by:

getPointOfAttachment in interface NoPutResultSet

Overrides:

getPointOfAttachment in class BasicNoPutResultSetImpl

Returns:

int Point of attachment (result set number) for this subquery. (-1 if not a subquery - also Sanity violation)

See Also:

• NoPutResultSet.getPointOfAttachment()

getTimeSpent

public long getTimeSpent(int type)

Return the total amount of time spent in this 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).