Class SingleItemFilter

    • Constructor Detail

      • SingleItemFilter

        public SingleItemFilter()
    • Method Detail

      • optimize

        public Expression optimize​(ExpressionVisitor visitor,
                                   ExpressionVisitor.ContextItemType 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 UnaryExpression
        Parameters:
        visitor - an expresion 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)
      • promote

        public Expression promote​(PromotionOffer offer,
                                  Expression parent)
                           throws XPathException
        Promote this expression if possible
        Overrides:
        promote in class UnaryExpression
        Parameters:
        offer - details of the offer, for example the offer to move expressions that don't depend on the context to an outer level in the containing expression
        parent - the containing expression in the expression tree
        Returns:
        if the offer is not accepted, return this expression unchanged. Otherwise return the result of rewriting the expression to promote this subexpression
        Throws:
        XPathException - if any error is detected