Package net.sf.saxon.expr.instruct
Class ComponentTracer
- java.lang.Object
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- net.sf.saxon.expr.Expression
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- net.sf.saxon.expr.instruct.Instruction
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- net.sf.saxon.expr.instruct.ComponentTracer
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- All Implemented Interfaces:
ExportAgent,TailCallReturner,Locatable,IdentityComparable,Traceable
public class ComponentTracer extends Instruction
A wrapper expression used to trace execution of components such as functions, templates, and global variables in XSLT and XQuery.
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Field Summary
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Fields inherited from class net.sf.saxon.expr.Expression
EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, MAX_COST, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, UPDATE_METHOD, WATCH_METHOD
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Constructor Summary
Constructors Constructor Description ComponentTracer(TraceableComponent component)Create a trace expression that traces execution of a given child expression
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description voidcheckForUpdatingSubexpressions()Check to ensure that this expression does not contain any inappropriate updating subexpressions.Expressioncopy(RebindingMap rebindings)Copy an expression.ItemevaluateItem(XPathContext context)Evaluate an expression as a single item.voidevaluatePendingUpdates(XPathContext context, PendingUpdateList pul)Evaluate an updating expression, adding the results to a Pending Update List.voidexport(ExpressionPresenter out)Export the expression structure.intgetCardinality()Determine the static cardinality of the expression.ExpressiongetChild()intgetDependencies()Determine which aspects of the context the expression depends on.java.lang.StringgetExpressionName()Get a name identifying the kind of expression, in terms meaningful to a user.intgetImplementationMethod()An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().intgetInstructionNameCode()Get the namecode of the instruction for use in diagnosticsItemTypegetItemType()Get the item type of the items returned by evaluating this instructionintgetNetCost()Return the estimated cost of evaluating an expression.java.lang.StringgetStreamerName()Get the (partial) name of a class that supports streaming of this kind of expressionbooleanisUpdatingExpression()Determine whether this is an updating expression as defined in the XQuery update specificationbooleanisVacuousExpression()Determine whether this is a vacuous expression as defined in the XQuery update specificationSequenceIteratoriterate(XPathContext context)Return an Iterator to iterate over the values of a sequence.booleanmayCreateNewNodes()Determine whether this instruction potentially creates new nodes.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.TailCallprocessLeavingTail(Outputter output, XPathContext context)Execute this instruction, with the possibility of returning tail calls if there are any.java.lang.StringtoShortString()Produce a short string identifying the expression for use in error messages-
Methods inherited from class net.sf.saxon.expr.instruct.Instruction
alwaysCreatesNewNodes, assembleParams, assembleTunnelParams, computeCardinality, computeSpecialProperties, dynamicError, evaluateAsString, getSourceLocator, isInstruction, isXSLT, process, someOperandCreatesNewNodes
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Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkPermittedContents, computeDependencies, computeHashCode, computeStaticProperties, dynamicError, effectiveBooleanValue, equals, explain, getConfiguration, getCost, getEvaluationMethod, getExtraProperty, getIntegerBounds, getInterpretedExpression, getIntrinsicDependencies, getLocalRetainedStaticContext, getLocation, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStaticUType, getTracingTag, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, markTailFunctionCalls, operandList, operandSparseList, optimize, optimizeChildren, prepareForStreaming, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, toString, typeCheck, typeCheckChildren, typeError, unordered, verifyParentPointers
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Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
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Methods inherited from interface net.sf.saxon.trace.Traceable
gatherProperties
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Constructor Detail
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ComponentTracer
public ComponentTracer(TraceableComponent component)
Create a trace expression that traces execution of a given child expression- Parameters:
component- the component whose entry and exit is to be traced.
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Method Detail
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getChild
public Expression getChild()
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operands
public java.lang.Iterable<Operand> operands()
Description copied from class:ExpressionGet the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression. Default implementation works off the results of iterateSubExpressions()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:
operandsin classInstruction- Returns:
- an iterator containing the sub-expressions of this expression
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getExpressionName
public java.lang.String getExpressionName()
Get a name identifying the kind of expression, in terms meaningful to a user.- Overrides:
getExpressionNamein classInstruction- 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.
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getStreamerName
public java.lang.String getStreamerName()
Get the (partial) name of a class that supports streaming of this kind of expression- Overrides:
getStreamerNamein classExpression- 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
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copy
public Expression copy(RebindingMap rebindings)
Description copied from class:ExpressionCopy an expression. This makes a deep copy.- Specified by:
copyin classExpression- 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
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isUpdatingExpression
public boolean isUpdatingExpression()
Determine whether this is an updating expression as defined in the XQuery update specification- Overrides:
isUpdatingExpressionin classExpression- Returns:
- true if this is an updating expression
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isVacuousExpression
public boolean isVacuousExpression()
Determine whether this is a vacuous expression as defined in the XQuery update specification- Overrides:
isVacuousExpressionin classExpression- Returns:
- true if this expression is vacuous
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checkForUpdatingSubexpressions
public void checkForUpdatingSubexpressions() throws XPathExceptionCheck to ensure that this expression does not contain any inappropriate updating subexpressions. This check is overridden for those expressions that permit updating subexpressions.- Overrides:
checkForUpdatingSubexpressionsin classExpression- Throws:
XPathException- if the expression has a non-permitted updating subexpression
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getImplementationMethod
public int getImplementationMethod()
Description copied from class:InstructionAn implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is prefered. For instructions this is the process() method.- Overrides:
getImplementationMethodin classInstruction- Returns:
- the implementation method, for example
Expression.ITERATE_METHODorExpression.EVALUATE_METHODorExpression.PROCESS_METHOD
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processLeavingTail
public TailCall processLeavingTail(Outputter output, XPathContext context) throws XPathException
Execute this instruction, with the possibility of returning tail calls if there are any. This outputs the trace information via the registered TraceListener, and invokes the instruction being traced.- Specified by:
processLeavingTailin interfaceTailCallReturner- Specified by:
processLeavingTailin classInstruction- Parameters:
output- the destination for the resultcontext- the dynamic execution context- Returns:
- either null, or a tail call that the caller must invoke on return
- Throws:
XPathException
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getItemType
public ItemType getItemType()
Get the item type of the items returned by evaluating this instruction- Overrides:
getItemTypein classInstruction- Returns:
- the static item type of the instruction
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getCardinality
public int getCardinality()
Determine the static cardinality of the expression. This establishes how many items there will be in the result of the expression, at compile time (i.e., without actually evaluating the result.- Overrides:
getCardinalityin classExpression- Returns:
- one of the values Cardinality.ONE_OR_MORE, Cardinality.ZERO_OR_MORE, Cardinality.EXACTLY_ONE, Cardinality.ZERO_OR_ONE, Cardinality.EMPTY. This default implementation returns ZERO_OR_MORE (which effectively gives no information).
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getDependencies
public int getDependencies()
Determine which aspects of the context the expression depends on. The result is a bitwise-or'ed value composed from constants such asStaticProperty.DEPENDS_ON_CONTEXT_ITEMandStaticProperty.DEPENDS_ON_CURRENT_ITEM. The default implementation combines the intrinsic dependencies of this expression with the dependencies of the subexpressions, computed recursively. This is overridden for expressions such as FilterExpression where a subexpression's dependencies are not necessarily inherited by the parent expression.- Overrides:
getDependenciesin classExpression- Returns:
- a set of bit-significant flags identifying the dependencies of the expression
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mayCreateNewNodes
public final boolean mayCreateNewNodes()
Determine whether this instruction potentially creates new nodes.- Overrides:
mayCreateNewNodesin classInstruction- Returns:
- true if the instruction creates new nodes under some input conditions (or if it can't be proved that it doesn't)
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getNetCost
public int getNetCost()
Return the estimated cost of evaluating an expression. For a TraceExpression we return zero, because ideally we don't want trace expressions to affect optimization decisions.- Overrides:
getNetCostin classInstruction- Returns:
- zero
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evaluateItem
public Item evaluateItem(XPathContext context) throws XPathException
Evaluate an expression as a single item. This always returns either a single Item or null (denoting the empty sequence). No conversion is done. This method should not be used unless the static type of the expression is a subtype of "item" or "item?": that is, it should not be called if the expression may return a sequence. There is no guarantee that this condition will be detected.- Overrides:
evaluateItemin classInstruction- Parameters:
context- The context in which the expression is to be evaluated- Returns:
- the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
- Throws:
XPathException- if any dynamic error occurs evaluating the expression
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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 handles iteration for expressions that return singleton values: for non-singleton expressions, the subclass must provide its own implementation.- Overrides:
iteratein classInstruction- 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
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getInstructionNameCode
public int getInstructionNameCode()
Description copied from class:InstructionGet the namecode of the instruction for use in diagnostics- Overrides:
getInstructionNameCodein classInstruction- Returns:
- a code identifying the instruction: typically but not always the fingerprint of a name in the XSLT namespace
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export
public void export(ExpressionPresenter out) throws XPathException
Export the expression structure. The abstract expression tree is written to the supplied output destination. Note: trace expressions are omitted from the generated SEF file.- Specified by:
exportin interfaceExportAgent- Specified by:
exportin classExpression- 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.
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evaluatePendingUpdates
public void evaluatePendingUpdates(XPathContext context, PendingUpdateList pul) throws XPathException
Evaluate an updating expression, adding the results to a Pending Update List. The default implementation of this method, which is used for non-updating expressions, throws an UnsupportedOperationException- Overrides:
evaluatePendingUpdatesin classExpression- Parameters:
context- the XPath dynamic evaluation contextpul- the pending update list to which the results should be written- Throws:
XPathException- if evaluation fails
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toShortString
public java.lang.String toShortString()
Produce a short string identifying the expression for use in error messages- Overrides:
toShortStringin classExpression- Returns:
- a short string, sufficient to identify the expression
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