Package net.sf.saxon.expr.sort

Class SortExpression

java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.sort.SortExpression
All Implemented Interfaces:
ExportAgent, Locatable, SortKeyEvaluator, IdentityComparable, Traceable
public class SortExpression extends Expression implements SortKeyEvaluator
Expression equivalent to the imaginary syntax expr sortby (sort-key)+

  • Constructor Details

    • 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 Details

    • getExpressionName

      public 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 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.

    • addSortKeyDetailsToPathMap

      public static void addSortKeyDetailsToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet, SortKeyDefinition skd)

    • 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

    • computeCardinality

      protected int computeCardinality()
      Determine the static cardinality
      Specified by:
      computeCardinality in class Expression
      Returns:
      the computed cardinality, as one of the values StaticProperty.ALLOWS_ZERO_OR_ONE, StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_MORE. May also return StaticProperty.ALLOWS_ZERO if the result is known to be an empty sequence, or StaticProperty.ALLOWS_MANY if if is known to return a sequence of length two or more.

    • 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

    • iterateSorted

      public SequenceIterator iterateSorted(SequenceIterator iter, XPathContext context) throws XPathException
      Throws:
      XPathException

    • makeSortKeyEvaluators

      public void makeSortKeyEvaluators()

    • evaluateSortKey

      public AtomicValue evaluateSortKey(int n, XPathContext c) throws XPathException
      Callback for evaluating the sort keys
      Specified by:
      evaluateSortKey in interface SortKeyEvaluator
      Parameters:
      n - the requested index
      c - the XPath context
      Returns:
      the evaluated sort key
      Throws:
      XPathException - if any error occurs

    • toShortString

      public 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 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.

    • getSelect

      public Expression getSelect()

    • setSelect

      public void setSelect(Expression select)

    • getSortKeyDefinitionList

      public SortKeyDefinitionList getSortKeyDefinitionList()

    • getSortKeyDefinition

      public SortKeyDefinition getSortKeyDefinition(int i)

    • setSortKeyDefinitionList

      public void setSortKeyDefinitionList(SortKeyDefinitionList skd)

    • getElaborator

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