org.h2.command.query

Class SelectGroups

java.lang.Object

org.h2.command.query.SelectGroups

public abstract class SelectGroups
extends java.lang.Object

Grouped data for aggregates.

Call sequence:

• reset().
• For each source row nextSource() should be invoked.
• done().
• next() is invoked inside a loop until it returns null.

Call sequence for lazy group sorted result:

• resetLazy() (not required before the first execution).
• For each source group nextLazyGroup() should be invoked.
• For each source row nextLazyRow() should be invoked. Each group can have one or more rows.

Method Summary

Modifier and Type	Method and Description
void	done() Invoked after all source rows are evaluated.
java.lang.Object	getCurrentGroupExprData(Expression expr) Get the group-by data for the current group and the passed in expression.
int	getCurrentGroupRowId() Returns identity of the current row.
static SelectGroups	getInstance(SessionLocal session, java.util.ArrayList<Expression> expressions, boolean isGroupQuery, int[] groupIndex) Creates new instance of grouped data.
PartitionData	getWindowExprData(DataAnalysisOperation expr, Value partitionKey) Get the window data for the specified expression.
boolean	isCurrentGroup() Is there currently a group-by active.
abstract ValueRow	next() Returns the key of the next group.
void	nextLazyGroup() Moves group data to the next group in lazy mode.
void	nextLazyRow() Moves group data to the next row in lazy mode.
abstract void	nextSource() Invoked for each source row to evaluate group key and setup all necessary data for aggregates.
void	remove() Removes the data for the current key.
void	reset() Resets this group data for reuse.
void	resetLazy() Resets this group data for reuse in lazy mode.
void	setCurrentGroupExprData(Expression expr, java.lang.Object obj) Set the group-by data for the current group and the passed in expression.
void	setWindowExprData(DataAnalysisOperation expr, Value partitionKey, PartitionData obj) Set the window data for the specified expression.

Methods inherited from class java.lang.Object

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

Method Detail

getInstance

public static SelectGroups getInstance(SessionLocal session,
                                       java.util.ArrayList<Expression> expressions,
                                       boolean isGroupQuery,
                                       int[] groupIndex)

Creates new instance of grouped data.

Parameters:

session - the session

expressions - the expressions

isGroupQuery - is this query is a group query

groupIndex - the indexes of group expressions, or null

Returns:

new instance of the grouped data.

isCurrentGroup

public boolean isCurrentGroup()

Is there currently a group-by active.

Returns:

true if there is currently a group-by active, otherwise returns false.

getCurrentGroupExprData

public final java.lang.Object getCurrentGroupExprData(Expression expr)

Get the group-by data for the current group and the passed in expression.

Parameters:

expr - expression

Returns:

expression data or null

setCurrentGroupExprData

public final void setCurrentGroupExprData(Expression expr,
                                          java.lang.Object obj)

Set the group-by data for the current group and the passed in expression.

Parameters:

expr - expression

obj - expression data to set

getWindowExprData

public final PartitionData getWindowExprData(DataAnalysisOperation expr,
                                             Value partitionKey)

Get the window data for the specified expression.

Parameters:

expr - expression

partitionKey - a key of partition

Returns:

expression data or null

setWindowExprData

public final void setWindowExprData(DataAnalysisOperation expr,
                                    Value partitionKey,
                                    PartitionData obj)

Set the window data for the specified expression.

Parameters:

expr - expression

partitionKey - a key of partition

obj - window expression data to set

getCurrentGroupRowId

public int getCurrentGroupRowId()

Returns identity of the current row. Used by aggregates to check whether they already processed this row or not.

Returns:

identity of the current row

reset

public void reset()

Resets this group data for reuse.

nextSource

public abstract void nextSource()

Invoked for each source row to evaluate group key and setup all necessary data for aggregates.

done

public void done()

Invoked after all source rows are evaluated.

next

public abstract ValueRow next()

Returns the key of the next group.

Returns:

the key of the next group, or null

remove

public void remove()

Removes the data for the current key.

See Also:

next()

resetLazy

public void resetLazy()

Resets this group data for reuse in lazy mode.

nextLazyGroup

public void nextLazyGroup()

Moves group data to the next group in lazy mode.

nextLazyRow

public void nextLazyRow()

Moves group data to the next row in lazy mode.