OnceResultSet (Apache Derby V10.14 Internals)

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

Field Summary

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

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.execute.NoPutResultSet
ABSOLUTE, FIRST, LAST, NEXT, PREVIOUS, RELATIVE, TEMPORARY_RESULT_SET_NUMBER

Fields inherited from class org.apache.derby.impl.sql.execute.NoPutResultSetImpl
checkNullCols, clonedExecRow, cncLen, resultSetNumber, targetResultSet

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

All Methods Instance Methods Concrete Methods
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 org.apache.derby.impl.sql.execute.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 org.apache.derby.impl.sql.execute.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 java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - 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 Detail
  - OnceResultSet
```
public OnceResultSet(NoPutResultSet s,
                     Activation a,
                     GeneratedMethod emptyRowFun,
                     int cardinalityCheck,
                     int resultSetNumber,
                     int subqueryNumber,
                     int pointOfAttachment,
                     double optimizerEstimatedRowCount,
                     double optimizerEstimatedCost)
```
- Method Detail
  - 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).

Class OnceResultSet

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.derby.impl.sql.execute.BasicNoPutResultSetImpl

Field Summary

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

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

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

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

Constructor Summary

Method Summary

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

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

Methods inherited from class java.lang.Object

Field Detail

DO_CARDINALITY_CHECK

NO_CARDINALITY_CHECK

UNIQUE_CARDINALITY_CHECK

rowWithNulls

statementContext

source

emptyRowFun

cardinalityCheck

subqueryNumber

pointOfAttachment

Constructor Detail

OnceResultSet

Method Detail

openCore

reopenCore

getNextRowCore

close

getPointOfAttachment

getTimeSpent