Class MergeResultSet

java.lang.Object

org.apache.derby.impl.sql.execute.NoRowsResultSetImpl

org.apache.derby.impl.sql.execute.MergeResultSet

All Implemented Interfaces:

ResultSet

class MergeResultSet
extends NoRowsResultSetImpl

INSERT/UPDATE/DELETE a target table based on how it outer joins with a driving table. For a description of how Derby processes the MERGE statement, see the header comment on MergeNode.

Field Summary

Fields

Modifier and Type	Field	Description
private MergeConstantAction	_constants
private NoPutResultSet	_drivingLeftJoin	////////////////////////////////////////////////////////////////////////////////
private int	_numOpens
private ExecRow	_row
private long	_rowCount
private BackingStoreHashtable	_subjectRowIDs
private TemporaryRowHolderImpl[]	_thenRows

Fields inherited from class NoRowsResultSetImpl

activation, beginExecutionTime, beginTime, endExecutionTime, endTime, lcc

Fields inherited from interface ResultSet

CURRENT_RESULTSET_ONLY, ENTIRE_RESULTSET_TREE, ISAFTERLAST, ISBEFOREFIRST, ISFIRST, ISLAST

Constructor Summary

Constructors

Constructor	Description
MergeResultSet(NoPutResultSet drivingLeftJoin, Activation activation)	Construct from a driving left join and an Activation.

Method Summary

Modifier and Type	Method	Description
private void	addSubjectRow(SQLRef subjectRowID)	Add another subject row id to the evolving hashtable of affected target rows.
void	cleanUp()	Tells the system to clean up on an error.
void	close()	Clean up resources and call close on data members.
(package private) boolean	collectAffectedRows()	Loop through the rows in the driving left join.
private void	createSubjectRowIDhashtable()	Create a BackingStoreHashtable to hold the ids of subject rows.
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().
final long	modifiedRowCount()	////////////////////////////////////////////////////////////////////////////////
void	open()	Needs to be called before the result set will do anything.
(package private) void	setup()	Set up the result set for use.

Methods inherited from class NoRowsResultSetImpl

addWarning, checkRowPosition, clearCurrentRow, close, doesCommit, evaluateGenerationClauses, getAbsoluteRow, getActivation, getAutoGeneratedKeysResultset, getBeginExecutionTimestamp, getCurrentTimeMillis, getCursorName, getEndExecutionTimestamp, getExecuteTime, getFirstRow, getLastRow, getNextRow, getPreviousRow, getQueryPlanText, getRelativeRow, getResultDescription, getRowNumber, getSubqueryTrackingArray, getTimeSpent, getWarnings, isClosed, returnsRows, setAfterLastRow, setBeforeFirstRow, toXML

Methods inherited from class Object

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

Field Details

_drivingLeftJoin

private NoPutResultSet _drivingLeftJoin

////////////////////////////////////////////////////////////////////////////////

_constants

private MergeConstantAction _constants

_row

private ExecRow _row

_rowCount

private long _rowCount

_thenRows

private TemporaryRowHolderImpl[] _thenRows

_subjectRowIDs

private BackingStoreHashtable _subjectRowIDs

_numOpens

private int _numOpens

Constructor Details

MergeResultSet

MergeResultSet(NoPutResultSet drivingLeftJoin,
 Activation activation)
        throws StandardException

Construct from a driving left join and an Activation.

Throws:

StandardException

Method Details

modifiedRowCount

public final long modifiedRowCount()

////////////////////////////////////////////////////////////////////////////////

Specified by:

modifiedRowCount in interface ResultSet

Overrides:

modifiedRowCount in class NoRowsResultSetImpl

Returns:

The number of rows affect by the statement, so far.

open

public void open()
          throws StandardException

Description copied from interface: ResultSet

Needs to be called before the result set will do anything. Need to call before getNextRow(), or for a result set that doesn't return rows, this is the call that will cause all the work to be done.

Throws:

StandardException - Thrown on failure

setup

void setup()
    throws StandardException

Description copied from class: NoRowsResultSetImpl

Set up the result set for use. Should always be called from open().

Overrides:

setup in class NoRowsResultSetImpl

Throws:

StandardException - thrown on error

close

public void close()
           throws StandardException

Clean up resources and call close on data members.

Throws:

StandardException - Thrown on error.

cleanUp

public void cleanUp()
             throws StandardException

Description copied from interface: ResultSet

Tells the system to clean up on an error.

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 NoRowsResultSetImpl

Throws:

StandardException - on error

collectAffectedRows

boolean collectAffectedRows()
                     throws StandardException

Loop through the rows in the driving left join.

Throws:

StandardException

addSubjectRow

private void addSubjectRow(SQLRef subjectRowID)
                    throws StandardException

Add another subject row id to the evolving hashtable of affected target rows. The concept of a subject row is defined by the 2011 SQL Standard, part 2, section 14.12 (merge statement), general rule 6. A row in the target table is a subject row if it joins to the source table on the main search condition and if the joined row satisfies the matching refinement condition for some WHEN MATCHED clause. A row in the target table may only be a subject row once. That is, a given target row may only qualify for UPDATE or DELETE processing once. If it qualifies for more than one UPDATE or DELETE action, then the Standard requires us to raise a cardinality violation.

Parameters:

subjectRowID - The location of the subject row.

Throws:

StandardException - A cardinality exception is thrown if we've already added this subject row.

createSubjectRowIDhashtable

private void createSubjectRowIDhashtable()
                                  throws StandardException

Create a BackingStoreHashtable to hold the ids of subject rows.

Throws:

StandardException