java.lang.Object
- net.sf.saxon.expr.flwor.Clause
- - net.sf.saxon.expr.flwor.GroupByClause

```
public class GroupByClause
extends Clause
```
This class represents an "group by" clause in a FLWOR expression

Nested Class Summary

Nested Classes
Modifier and Type	Class	Description
`static class`	`GroupByClause.ObjectToBeGrouped`	Inner class representing the contents of a tuple from the pre-grouping tuple stream; a set of such objects consitutes a group.
`class`	`GroupByClause.TupleComparisonKey`	Inner class representing a tuple comparison key: that is, an arbitrary object whose equals() and hashCode() methods can be used to test whether two tuples have equivalent grouping keys

Nested classes/interfaces inherited from class net.sf.saxon.expr.flwor.Clause
Clause.ClauseName

Constructor Summary

Constructors
Constructor Description

GroupByClause(Configuration config)
Create a group-by clause

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)`	Collect information about the navigation paths followed by this clause, for document projection purposes
`boolean`	`containsNonInlineableVariableReference(Binding binding)`	Determine whether the clause contains a reference to a local variable binding that cannot be inlined
`GroupByClause`	`copy(FLWORExpression flwor, RebindingMap rebindings)`	Create a copy of this clause
`void`	`explain(ExpressionPresenter out)`	Diagnostic print of expression structure.
`Clause.ClauseName`	`getClauseKey()`	Get a keyword identifying what kind of clause this is
`GroupByClause.TupleComparisonKey`	`getComparisonKey(Tuple t, GenericAtomicComparer[] comparers)`	Callback to get the comparison key for a tuple.
`TupleExpression`	`getGroupingTupleExpression()`	Get the tuple expression that evaluates all the grouping variables, returning the values these variables take in the input stream
`TuplePull`	`getPullStream(TuplePull base, XPathContext context)`	Get a tuple stream that implements the functionality of this clause, taking its input from another tuple stream which this clause modifies
`TuplePush`	`getPushStream(TuplePush destination, Outputter output, XPathContext context)`	Get a push-mode tuple stream that implements the functionality of this clause, supplying its output to another tuple stream
`LocalVariableBinding[]`	`getRangeVariables()`	Get the variables bound by this clause
`TupleExpression`	`getRetainedTupleExpression()`	Get the tuple expression that evaluates all the non-grouping variables, returning the values these variables take in the grouping input stream
`void`	`initGroupingTupleExpression(FLWORExpression flwor, TupleExpression expr)`	Initialize a tuple expression that evaluates all the grouping variables, returning the values these variables take in the input stream
`void`	`initRetainedTupleExpression(FLWORExpression flwor, TupleExpression expr)`	Initialize a tuple expression that evaluates all the non-grouping variables, returning the values these variables take in the grouping input stream
`void`	`optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType)`	Optimize any expressions contained within this clause
`void`	`processGroup(java.util.List<GroupByClause.ObjectToBeGrouped> group, XPathContext context)`	Process a group of tuples from the input stream to generate a single tuple in the output stream.
`void`	`processOperands(OperandProcessor processor)`	Process the subexpressions of this clause
`void`	`setComparers(GenericAtomicComparer[] comparers)`	Set the comparers used for the grouping keys.
`void`	`setGroupingTupleExpression(TupleExpression expr)`	Set a tuple expression that evaluates all the grouping variables, returning the values these variables take in the input stream
`void`	`setRetainedTupleExpression(TupleExpression expr)`	Set a tuple expression that evaluates all the non-grouping variables, returning the values these variables take in the grouping input stream
`void`	`setVariableBindings(LocalVariableBinding[] bindings)`	Set the bindings of new variables created by the grouping clause, which constitute the variables appearing in the output (post-grouping) tuple stream.
`java.lang.String`	`toString()`

Methods inherited from class net.sf.saxon.expr.flwor.Clause
gatherVariableReferences, getConfiguration, getLocation, getPackageData, getTraceInfo, isRepeated, refineVariableType, setLocation, setPackageData, setRepeated, toShortString, typeCheck

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - GroupByClause
```
public GroupByClause(Configuration config)
```
    Create a group-by clause
    
    Parameters:
    
    config - the Saxon configuration
- Method Detail
  - getClauseKey
```
public Clause.ClauseName getClauseKey()
```
    Description copied from class: Clause
    
    Get a keyword identifying what kind of clause this is
    
    Specified by:
    
    getClauseKey in class Clause
    
    Returns:
    
    the kind of clause
  - containsNonInlineableVariableReference
```
public boolean containsNonInlineableVariableReference(Binding binding)
```
    Description copied from class: Clause
    
    Determine whether the clause contains a reference to a local variable binding that cannot be inlined
    
    Overrides:
    
    containsNonInlineableVariableReference in class Clause
    
    Parameters:
    
    binding - the binding for the local variable in question
    
    Returns:
    
    true if this clause uses the variable in a way that does not permit inlining
  - copy
```
public GroupByClause copy(FLWORExpression flwor,
                          RebindingMap rebindings)
```
    Description copied from class: Clause
    
    Create a copy of this clause
    
    Specified by:
    
    copy in class Clause
    
    Parameters:
    
    flwor - the new FLWORExpression to contain the copied clause
    
    Returns:
    
    the copied clause
  - initRetainedTupleExpression
```
public void initRetainedTupleExpression(FLWORExpression flwor,
                                        TupleExpression expr)
```
    Initialize a tuple expression that evaluates all the non-grouping variables, returning the values these variables take in the grouping input stream
    
    Parameters:
    
    flwor - the containing FLWORExpression
    
    expr - the tuple expression
  - setRetainedTupleExpression
```
public void setRetainedTupleExpression(TupleExpression expr)
```
    Set a tuple expression that evaluates all the non-grouping variables, returning the values these variables take in the grouping input stream
    
    Parameters:
    
    expr - the tuple expression
  - getRetainedTupleExpression
```
public TupleExpression getRetainedTupleExpression()
```
    Get the tuple expression that evaluates all the non-grouping variables, returning the values these variables take in the grouping input stream
    
    Returns:
    
    the tuple expression
  - optimize
```
public void optimize(ExpressionVisitor visitor,
                     ContextItemStaticInfo contextItemType)
              throws XPathException
```
    Description copied from class: Clause
    
    Optimize any expressions contained within this clause
    
    Overrides:
    
    optimize in class Clause
    
    Parameters:
    
    visitor - the ExpressionVisitor, providing access to static context information
    
    contextItemType - the type of the context item
    
    Throws:
    
    XPathException - if any error is detected
  - initGroupingTupleExpression
```
public void initGroupingTupleExpression(FLWORExpression flwor,
                                        TupleExpression expr)
```
    Initialize a tuple expression that evaluates all the grouping variables, returning the values these variables take in the input stream
    
    Parameters:
    
    flwor - the containing FLWORExpression
    
    expr - the tuple expression
  - setGroupingTupleExpression
```
public void setGroupingTupleExpression(TupleExpression expr)
```
    Set a tuple expression that evaluates all the grouping variables, returning the values these variables take in the input stream
    
    Parameters:
    
    expr - the tuple expression
  - getGroupingTupleExpression
```
public TupleExpression getGroupingTupleExpression()
```
    Get the tuple expression that evaluates all the grouping variables, returning the values these variables take in the input stream
    
    Returns:
    
    the tuple expression
  - setVariableBindings
```
public void setVariableBindings(LocalVariableBinding[] bindings)
```
    Set the bindings of new variables created by the grouping clause, which constitute the variables appearing in the output (post-grouping) tuple stream. There will be one of these for each variable in the input (pre-grouping) stream; by convention the bindings for grouping variables precede the bindings for non-grouping (retained) variables, and the order is preserved.
    
    Parameters:
    
    bindings - the bindings of the variables created in the output stream
  - getRangeVariables
```
public LocalVariableBinding[] getRangeVariables()
```
    Get the variables bound by this clause
    
    Overrides:
    
    getRangeVariables in class Clause
    
    Returns:
    
    the variable bindings
  - setComparers
```
public void setComparers(GenericAtomicComparer[] comparers)
```
    Set the comparers used for the grouping keys. There is one comparer for each grouping variable
    
    Parameters:
    
    comparers - the comparers for grouping keys.
  - getPullStream
```
public TuplePull getPullStream(TuplePull base,
                               XPathContext context)
```
    Get a tuple stream that implements the functionality of this clause, taking its input from another tuple stream which this clause modifies
    
    Specified by:
    
    getPullStream in class Clause
    
    Parameters:
    
    base - the input tuple stream
    
    context - the XPath dynamic evaluation context
    
    Returns:
    
    the output tuple stream
  - getPushStream
```
public TuplePush getPushStream(TuplePush destination,
                               Outputter output,
                               XPathContext context)
```
    Get a push-mode tuple stream that implements the functionality of this clause, supplying its output to another tuple stream
    
    Specified by:
    
    getPushStream in class Clause
    
    Parameters:
    
    destination - the output tuple stream
    
    output - the destination for the result
    
    context - the dynamic evaluation context
    
    Returns:
    
    the push tuple stream that implements the functionality of this clause of the FLWOR expression
  - processOperands
```
public void processOperands(OperandProcessor processor)
                     throws XPathException
```
    Process the subexpressions of this clause
    
    Specified by:
    
    processOperands in class Clause
    
    Parameters:
    
    processor - the expression processor used to process the subexpressions
    
    Throws:
    
    XPathException - if any error is detected
  - explain
```
public void explain(ExpressionPresenter out)
```
    Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
    
    Specified by:
    
    explain in class Clause
    
    Parameters:
    
    out - the expression presenter used to display the structure
  - toString
```
public java.lang.String toString()
```
    Overrides:
    
    toString in class java.lang.Object
  - processGroup
```
public void processGroup(java.util.List<GroupByClause.ObjectToBeGrouped> group,
                         XPathContext context)
                  throws XPathException
```
    Process a group of tuples from the input stream to generate a single tuple in the output stream. This method takes a group of tuples as input, and sets all the required variables in the local stack frame as required to deliver this group as the current tuple in the post-grouping stream
    
    Parameters:
    
    group - the group of input tuples
    
    context - the XPath dynamic evaluation context
    
    Throws:
    
    XPathException - if a dynamic error occurs
  - getComparisonKey
```
public GroupByClause.TupleComparisonKey getComparisonKey(Tuple t,
                                                         GenericAtomicComparer[] comparers)
```
    Callback to get the comparison key for a tuple. Two tuples are equal if their comparison keys compare equal using the equals() method.
    
    Parameters:
    
    t - the tuple whose comparison key is required
    
    Returns:
    
    a comparison key suitable for comparing with other tuples
  - addToPathMap
```
public void addToPathMap(PathMap pathMap,
                         PathMap.PathMapNodeSet pathMapNodeSet)
```
    Description copied from class: Clause
    
    Collect information about the navigation paths followed by this clause, for document projection purposes
    
    Specified by:
    
    addToPathMap in class Clause
    
    Parameters:
    
    pathMap - the path map in which the data is to be collected
    
    pathMapNodeSet - the path map node set representing the paths to the context item

Class GroupByClause

Nested Class Summary

Nested classes/interfaces inherited from class net.sf.saxon.expr.flwor.Clause

Constructor Summary

Method Summary

Methods inherited from class net.sf.saxon.expr.flwor.Clause

Methods inherited from class java.lang.Object

Constructor Detail

GroupByClause

Method Detail

getClauseKey

containsNonInlineableVariableReference

copy

initRetainedTupleExpression

setRetainedTupleExpression

getRetainedTupleExpression

optimize

initGroupingTupleExpression

setGroupingTupleExpression

getGroupingTupleExpression

setVariableBindings

getRangeVariables

setComparers

getPullStream

getPushStream

processOperands

explain

toString

processGroup

getComparisonKey

addToPathMap