Package net.sf.saxon.expr.sort

Class MergeInstr

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.instruct.Instruction

net.sf.saxon.expr.sort.MergeInstr

All Implemented Interfaces:

ExportAgent, TailCallReturner, Locatable, IdentityComparable, Traceable

public class MergeInstr
extends Instruction

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	MergeInstr.MergeKeyMappingFunction	Mapping function for items encountered during the merge; the mapping function wraps the merged item and its merge keys into a single composite object
static class	MergeInstr.MergeSource	Inner class representing one merge source

Field Summary

Fields

Modifier and Type	Field	Description
protected AtomicComparer[]	comparators
protected MergeInstr.MergeSource[]	mergeSources

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

Constructor Summary

Constructors

Constructor	Description
MergeInstr()

Method Summary

Modifier and Type	Method	Description
boolean	allowExtractingCommonSubexpressions()	Ask whether common subexpressions found in the operands of this expression can be extracted and evaluated outside the expression itself.
void	checkPermittedContents(SchemaType parentType, boolean whole)	Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type.
Expression	copy(RebindingMap rebindings)	Copy an expression.
void	export(ExpressionPresenter out)	Diagnostic print of expression structure.
void	fixupGroupReferences()
Expression	getAction()
java.util.Comparator<ObjectValue<ItemWithMergeKeys>>	getComparer(SortKeyDefinitionList sKeys, AtomicComparer[] comps)
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)
int	getInstructionNameCode()	Get the namecode of the instruction for use in diagnostics
ItemType	getItemType()	Get the item type of the items returned by evaluating this instruction
MergeInstr.MergeSource[]	getMergeSources()
java.lang.String	getStreamerName()	Get the (partial) name of a class that supports streaming of this kind of expression
MergeInstr	init(MergeInstr.MergeSource[] mSources, Expression action)	Initialise the merge instruction
SequenceIterator	iterate(XPathContext context)	Return an Iterator to iterate over the values of a sequence.
boolean	mayCreateNewNodes()	Determine whether this instruction 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.
Expression	optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)	Perform optimisation of an expression and its subexpressions.
void	prepareForStreaming()
TailCall	processLeavingTail(Outputter output, XPathContext context)	ProcessLeavingTail: called to do the real work of this instruction.
void	setAction(Expression action)
Expression	typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)	Perform type checking of an expression and its subexpressions.

Methods inherited from class net.sf.saxon.expr.instruct.Instruction

alwaysCreatesNewNodes, assembleParams, assembleTunnelParams, computeCardinality, computeSpecialProperties, dynamicError, evaluateAsString, evaluateItem, getExpressionName, getImplementationMethod, getNetCost, getSourceLocator, isInstruction, isXSLT, process, someOperandCreatesNewNodes

Methods inherited from class net.sf.saxon.expr.Expression

addToPathMap, adoptChildExpression, checkedOperands, checkForUpdatingSubexpressions, computeDependencies, computeHashCode, computeStaticProperties, dynamicError, effectiveBooleanValue, equals, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getCost, getDependencies, 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, isUpdatingExpression, isVacuousExpression, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, toShortString, toString, typeCheckChildren, typeError, unordered, verifyParentPointers

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface net.sf.saxon.trace.Traceable

gatherProperties

Field Detail

mergeSources

protected MergeInstr.MergeSource[] mergeSources

comparators

protected AtomicComparer[] comparators

Constructor Detail

MergeInstr

public MergeInstr()

Method Detail

init

public MergeInstr init(MergeInstr.MergeSource[] mSources,
                       Expression action)

Initialise the merge instruction

Parameters:

mSources - the set of merge source definitions

action - the action to be performed on each group of items with identical merge keys

Returns:

the merge instruction (to allow call chaining)

getMergeSources

public MergeInstr.MergeSource[] getMergeSources()

setAction

public void setAction(Expression action)

getAction

public Expression getAction()

getInstructionNameCode

public int getInstructionNameCode()

Get the namecode of the instruction for use in diagnostics

Overrides:

getInstructionNameCode in class Instruction

Returns:

a code identifying the instruction: typically but not always the fingerprint of a name in the XSLT namespace

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

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

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

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)

fixupGroupReferences

public void fixupGroupReferences()

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)

optimize

public Expression optimize(ExpressionVisitor visitor,
                           ContextItemStaticInfo contextInfo)
                    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

contextInfo - 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)

prepareForStreaming

public void prepareForStreaming()
                         throws XPathException

Overrides:

prepareForStreaming in class Expression

Throws:

XPathException

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException

Description copied from class: Instruction

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:

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

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.

Specified by:

operands in class Instruction

Returns:

an iterator containing the sub-expressions of this expression

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

getComparer

public java.util.Comparator<ObjectValue<ItemWithMergeKeys>> getComparer(SortKeyDefinitionList sKeys,
                                                                        AtomicComparer[] comps)

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

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.

processLeavingTail

public TailCall processLeavingTail(Outputter output,
                                   XPathContext context)
                            throws XPathException

Description copied from class: Instruction

ProcessLeavingTail: called to do the real work of this instruction. This method must be implemented in each subclass. The results of the instruction are written to the current Receiver, which can be obtained via the Controller.

Specified by:

processLeavingTail in interface TailCallReturner

Specified by:

processLeavingTail in class Instruction

Parameters:

output - the destination for the result

context - The dynamic context of the transformation, giving access to the current node, the current variables, etc.

Returns:

null if the instruction has completed execution; or a TailCall indicating a function call or template call that is delegated to the caller, to be made after the stack has been unwound so as to save stack space.

Throws:

XPathException - if a dynamic error occurs during the evaluation of the instruction

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