Package net.sf.saxon.expr.instruct

Class ForEachGroup

java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.instruct.Instruction
net.sf.saxon.expr.instruct.ForEachGroup
All Implemented Interfaces:
ContextOriginator, ContextSwitchingExpression, ExportAgent, Locatable, SortKeyEvaluator, IdentityComparable, Traceable
public class ForEachGroup extends Instruction implements SortKeyEvaluator, ContextSwitchingExpression
Handler for xsl:for-each-group elements in stylesheet. This is a new instruction defined in XSLT 2.0

  • Field Details

  • Constructor Details

    • ForEachGroup

      public ForEachGroup(Expression select, Expression action, byte algorithm, Expression key, StringCollator collator, Expression collationNameExpression, SortKeyDefinitionList sortKeys)
      Create a for-each-group instruction
      Parameters:
      select - the select expression (selects the population to be grouped)
      action - the body of the for-each-group (applied to each group in turn)
      algorithm - one of group-by, group-adjacent, group-starting-with, group-ending-with
      key - expression to evaluate the grouping key
      collator - user for comparing strings
      collationNameExpression - expression that yields the name of the collation to be used
      sortKeys - list of xsl:sort keys for sorting the groups. May be null.

  • Method Details

    • getInstructionNameCode

      public int getInstructionNameCode()
      Get the name of this instruction for diagnostic and tracing purposes
      Overrides:
      getInstructionNameCode in class Instruction
      Returns:
      the name of the instruction

    • operands

      public Iterable<Operand> operands()
      Description copied from class: Expression
      Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.

      If the expression is a Callable, then it is required that the order of the operands returned by this function is the same as the order of arguments supplied to the corresponding call() method.

      Specified by:
      operands in class Instruction
      Returns:
      an iterator containing the sub-expressions of this expression

    • getSelectExpression

      public Expression getSelectExpression()
      Get the select expression
      Specified by:
      getSelectExpression in interface ContextSwitchingExpression
      Returns:
      the select expression

    • getActionExpression

      public Expression getActionExpression()
      Get the action expression (the content of the for-each-group)
      Specified by:
      getActionExpression in interface ContextSwitchingExpression
      Returns:
      the body of the xsl:for-each-group instruction

    • getAlgorithm

      public byte getAlgorithm()
      Get the grouping algorithm (one of group-by, group-adjacent, group-starting-with, group-ending-with)
      Returns:
      one of group-by, group-adjacent, group-starting-with, group-ending-with

    • getGroupingKey

      public Expression getGroupingKey()
      Get the grouping key expression expression (the group-by or group-adjacent expression, or a PatternSponsor containing the group-starting-with or group-ending-with expression)
      Returns:
      the expression used to calculate grouping keys

    • getSortKeyDefinitions

      public SortKeyDefinitionList getSortKeyDefinitions()
      Get the sort keys defined at the for-each-group level, that is, the keys for sorting the groups
      Returns:
      the definitions of the sort keys defined as children of the xsl:for-each-group element, or null if there are no sort keys

    • getSortKeyComparators

      public AtomicComparer[] getSortKeyComparators()
      Get the statically-allocated sort key comparators for sorting at the group level, if known
      Returns:
      the comparators used for comparing sort key values, one entry in the array for each nested xsl:sort element

    • getCollation

      public StringCollator getCollation()
      Get the statically-determined collator, or null if the collation was not determined statically
      Returns:
      the collation, if known statically, or null if not

    • getBaseURI

      public URI getBaseURI()
      Get the static base URI of the instruction
      Returns:
      the static base URI if known, or null otherwise

    • isComposite

      public boolean isComposite()

    • setComposite

      public void setComposite(boolean composite)

    • isInFork

      public boolean isInFork()

    • setIsInFork

      public void setIsInFork(boolean inFork)

    • allowExtractingCommonSubexpressions

      public boolean allowExtractingCommonSubexpressions()
      Ask whether common subexpressions found in the operands of this expression can be extracted and evaluated outside the expression itself. The result is irrelevant in the case of operands evaluated with a different focus, which will never be extracted in this way, even if they have no focus dependency.
      Overrides:
      allowExtractingCommonSubexpressions in class Expression
      Returns:
      false for this kind of expression

    • typeCheck

      public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException
      Description copied from class: Expression
      Perform type checking of an expression and its subexpressions. This is the second phase of static optimization.

      This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.

      This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables may not be accurately known if they have not been explicitly declared.

      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
      Description copied from class: Expression
      Perform optimisation of an expression and its subexpressions. This is the third and final phase of static optimization.

      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 - a mutable list of (old binding, new binding) pairs that is used to update the bindings held in any local variable references that are copied.
      Returns:
      the copy of the original expression

    • getItemType

      public ItemType getItemType()
      Get the item type of the items returned by evaluating this instruction
      Overrides:
      getItemType in class Instruction
      Returns:
      the static item type of the instruction

    • computeDependencies

      public int computeDependencies()
      Compute the dependencies of an expression, as the union of the dependencies of its subexpressions. (This is overridden for path expressions and filter expressions, where the dependencies of a subexpression are not all propogated). This method should be called only once, to compute the dependencies; after that, getDependencies should be used.
      Overrides:
      computeDependencies in class Expression
      Returns:
      the depencies, as a bit-mask

    • computeSpecialProperties

      protected int computeSpecialProperties()
      Get the static properties of this expression (other than its type). The result is bit-signficant. 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 Instruction
      Returns:
      a set of flags indicating static properties of this expression

    • mayCreateNewNodes

      public final boolean mayCreateNewNodes()
      Determine whether this instruction creates new nodes. This implementation returns true if the "action" creates new nodes. (Nodes created by the condition can't contribute to the result).
      Overrides:
      mayCreateNewNodes in class Instruction
      Returns:
      true if the instruction creates new nodes under some input conditions (or if it can't be proved that it doesn't)

    • 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

    • 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 set of nodes within the path map
      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.

    • checkPermittedContents

      public void checkPermittedContents(SchemaType parentType, boolean whole) throws XPathException
      Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type. It's always OK to say yes, since the check will be repeated at run-time. The process of checking element and attribute constructors against the content model of a complex type also registers the type of content expected of those constructors, so the static validation can continue recursively.
      Overrides:
      checkPermittedContents in class Expression
      Parameters:
      parentType - the "given complex type": the method is checking that the nodes returned by this expression are acceptable members of the content model of this type
      whole - if true, we want to check that the value of this expression satisfies the content model as a whole; if false we want to check that the value of the expression is acceptable as one part of the content
      Throws:
      XPathException - if the value delivered by this expression cannot be part of the content model of the given type

    • getCollationNameExpression

      public Expression getCollationNameExpression()
      Get the expression which, on evaluation, yields the name of the collation to be used
      Returns:
      the expression that returns the collation name

    • getGroupIterator

      public GroupIterator getGroupIterator(PullEvaluator selectPull, XPathContext context) throws XPathException
      Throws:
      XPathException

    • iterate

      public SequenceIterator iterate(XPathContext context) throws XPathException
      Return an Iterator to iterate over the values of a sequence. The value of every expression can be regarded as a sequence, so this method is supported for all expressions. This default implementation relies on the process() method: it "pushes" the results of the instruction to a sequence in memory, and then iterates over this in-memory sequence.

      In principle instructions should implement a pipelined iterate() method that avoids the overhead of intermediate storage.

      Overrides:
      iterate in class Instruction
      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

    • 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

    • getSortKeyDefinitionList

      public SortKeyDefinitionList getSortKeyDefinitionList()

    • 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)

    • setAction

      public void setAction(Expression action)

    • setKey

      public void setKey(Expression key)

    • setCollationNameExpression

      public void setCollationNameExpression(Expression collationNameExpression)

    • getElaborator

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