Package net.sf.saxon.expr.sort

Class SortExpression

    • Constructor Detail

      • SortExpression

        public SortExpression​(Expression select,
                      SortKeyDefinitionList sortKeys)
        Create a sort expression
        Parameters:
        select - the expression whose result is to be sorted
        sortKeys - the set of sort key definitions to be used, in major to minor order

    • Method Detail

      • getExpressionName

        public java.lang.String getExpressionName()
        Get a name identifying the kind of expression, in terms meaningful to a user.
        Overrides:
        getExpressionName in class Expression
        Returns:
        a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in explain() output displaying the expression.

      • getBaseOperand

        public Operand getBaseOperand()
        Get the operand representing the expression being sorted
        Returns:
        the operand representing the expression being sorted

      • getBaseExpression

        public Expression getBaseExpression()
        Get the expression defining the sequence being sorted
        Returns:
        the expression whose result is to be sorted

      • getComparators

        public AtomicComparer[] getComparators()
        Get the comparators, if known statically. Otherwise, return null.
        Returns:
        The comparators, if they have been allocated; otherwise null

      • operands

        public java.lang.Iterable<Operand> operands()
        Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression. Default implementation returns a zero-length array, appropriate for an expression that has no sub-expressions.
        Overrides:
        operands in class Expression
        Returns:
        an iterator containing the sub-expressions of this expression

      • addToPathMap

        public PathMap.PathMapNodeSet addToPathMap​(PathMap pathMap,
                                           PathMap.PathMapNodeSet pathMapNodeSet)
        Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited by an expression in a source tree.

        The default implementation of this method assumes that an expression does no navigation other than the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the same context as the containing expression. The method must be overridden for any expression where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression, and RootExpression (because they perform navigation), and for the doc(), document(), and collection() functions because they create a new navigation root. Implementations also exist for PathExpression and FilterExpression because they have subexpressions that are evaluated in a different context from the calling expression.

        Overrides:
        addToPathMap in class Expression
        Parameters:
        pathMap - the PathMap to which the expression should be added
        pathMapNodeSet - the PathMapNodeSet to which the paths embodied in this expression should be added
        Returns:
        the pathMapNode representing the focus established by this expression, in the case where this expression is the first operand of a path expression or filter expression. For an expression that does navigation, it represents the end of the arc in the path map that describes the navigation route. For other expressions, it is the same as the input pathMapNode.

      • typeCheck

        public Expression typeCheck​(ExpressionVisitor visitor,
                            ContextItemStaticInfo contextInfo)
                     throws XPathException
        Type-check the expression
        Overrides:
        typeCheck in class Expression
        Parameters:
        visitor - an expression visitor
        contextInfo - Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.
        Returns:
        the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
        Throws:
        XPathException - if an error is discovered during this phase (typically a type error)

      • optimize

        public Expression optimize​(ExpressionVisitor visitor,
                           ContextItemStaticInfo contextItemType)
                    throws XPathException
        Perform optimisation of an expression and its subexpressions.

        This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

        Overrides:
        optimize in class Expression
        Parameters:
        visitor - an expression visitor
        contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE
        Returns:
        the original expression, rewritten if appropriate to optimize execution
        Throws:
        XPathException - if an error is discovered during this phase (typically a type error)

      • copy

        public Expression copy​(RebindingMap rebindings)
        Copy an expression. This makes a deep copy.
        Specified by:
        copy in class Expression
        Parameters:
        rebindings - variables that need to be re-bound
        Returns:
        the copy of the original expression

      • isSortKey

        public boolean isSortKey​(Expression child)
        Test whether a given expression is one of the sort keys
        Parameters:
        child - the given expression
        Returns:
        true if the given expression is one of the sort keys

      • getItemType

        public ItemType getItemType()
        Determine the data type of the items returned by the expression, if possible
        Specified by:
        getItemType in class Expression
        Returns:
        a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known in advance)

      • computeSpecialProperties

        protected int computeSpecialProperties()
        Get the static properties of this expression (other than its type). The result is bit-significant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.
        Overrides:
        computeSpecialProperties in class Expression
        Returns:
        the special properties, as a bit-significant integer

      • getImplementationMethod

        public int getImplementationMethod()
        An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.
        Specified by:
        getImplementationMethod in class Expression
        Returns:
        the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

      • iterate

        public SequenceIterator iterate​(XPathContext context)
                         throws XPathException
        Enumerate the results of the expression
        Overrides:
        iterate in class Expression
        Parameters:
        context - supplies the context for evaluation
        Returns:
        a SequenceIterator that can be used to iterate over the result of the expression
        Throws:
        XPathException - if any dynamic error occurs evaluating the expression

      • makeSortKeyEvaluators

        public void makeSortKeyEvaluators()

      • toShortString

        public java.lang.String toShortString()
        Description copied from class: Expression
        Produce a short string identifying the expression for use in error messages
        Overrides:
        toShortString in class Expression
        Returns:
        a short string, sufficient to identify the expression

      • getStreamerName

        public java.lang.String getStreamerName()
        Get the (partial) name of a class that supports streaming of this kind of expression
        Overrides:
        getStreamerName in class Expression
        Returns:
        the partial name of a class that can be instantiated to provide streaming support in Saxon-EE, or null if there is no such class

      • export

        public void export​(ExpressionPresenter out)
            throws XPathException
        Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
        Specified by:
        export in interface ExportAgent
        Specified by:
        export in class Expression
        Parameters:
        out - the expression presenter used to display the structure
        Throws:
        XPathException - if the export fails, for example if an expression is found that won't work in the target environment.

      • setSelect

        public void setSelect​(Expression select)

      • getElaborator

        public Elaborator getElaborator()
        Make an elaborator for this expression
        Overrides:
        getElaborator in class Expression
        Returns:
        a suitable elaborator