Class GroupByClause


  • public class GroupByClause
    extends Clause
    This class represents an "group by" clause in a FLWOR expression
    • 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
        rebindings - the rebinding map
        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
      • 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
        comparers - array of comparers for comparing each component of the grouping key
        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