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:

ContextMappingFunction, ContextOriginator, ContextSwitchingExpression, TailCallReturner, SortKeyEvaluator, IdentityComparable

public class ForEachGroup
extends Instruction
implements SortKeyEvaluator, ContextMappingFunction, ContextSwitchingExpression

Handler for xsl:for-each-group elements in stylesheet. This is a new instruction defined in XSLT 2.0

Field Summary

Fields

Modifier and Type	Field and Description
static int	GROUP_ADJACENT
static int	GROUP_BY
static int	GROUP_ENDING
static int	GROUP_STARTING

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

EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, UPDATE_METHOD, WATCH_METHOD

Constructor Summary

Constructors

Constructor and Description
ForEachGroup(Expression select, Expression action, byte algorithm, Expression key, StringCollator collator, Expression collationNameExpression, SortKeyDefinitionList sortKeys) Create a for-each-group instruction

Method Summary

Methods

Modifier and Type	Method and Description
PathMap.PathMapNodeSet	addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet) Add a representation of this expression to a PathMap.
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.
int	computeDependencies() Compute the dependencies of an expression, as the union of the dependencies of its subexpressions.
int	computeSpecialProperties() Get the static properties of this expression (other than its type).
Expression	copy() Copy an expression.
boolean	createsNewNodes() Determine whether this instruction creates new nodes.
AtomicValue	evaluateSortKey(int n, XPathContext c) Callback for evaluating the sort keys
void	export(ExpressionPresenter out) Diagnostic print of expression structure.
Expression	getActionExpression() Get the action expression (the content of the for-each-group)
byte	getAlgorithm() Get the grouping algorithm (one of group-by, group-adjacent, group-starting-with, group-ending-with)
AtomicComparer	getAtomicComparer(XPathContext context)
URI	getBaseURI() Get the static base URI of the instruction
StringCollator	getCollation() Get the statically-determined collator, or null if the collation was not determined statically
Expression	getCollationNameExpression() Get the expression which, on evaluation, yields the name of the collation to be used
ExpressionCompiler	getExpressionCompiler() Return the compiler of the ForEachGroup expression
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 name of this instruction for diagnostic and tracing purposes
ItemType	getItemType() Get the item type of the items returned by evaluating this instruction
int	getKeyItemType() Get the primitive item type of the key
Expression	getSelectExpression() Get the select expression
AtomicComparer[]	getSortKeyComparators() Get the statically-allocated sort key comparators for sorting at the group level, if known
SortKeyDefinitionList	getSortKeyDefinitionList()
SortKeyDefinitionList	getSortKeyDefinitions() Get the sort keys defined at the for-each-group level, that is, the keys for sorting the groups
StreamingAdjunct	getStreamingAdjunct() Get a class that supports streamed evaluation of this expression
boolean	isComposite()
SequenceIterator	iterate(XPathContext context) Return an Iterator to iterate over the values of a sequence.
SequenceIterator	map(XPathContext context) Map one item to a sequence.
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 contextItemType) Perform optimisation of an expression and its subexpressions.
TailCall	processLeavingTail(XPathContext context) ProcessLeavingTail: called to do the real work of this instruction.
protected void	promoteChildren(PromotionOffer offer) Handle promotion offers, that is, non-local tree rewrites.
void	setAction(Expression action)
void	setCollationNameExpression(Expression collationNameExpression)
void	setComposite(boolean composite)
void	setKey(Expression key)
void	setSelect(Expression select)
void	setSortKeyDefinitions(SortKeyDefinitionList sortKeyDefinitions)
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

assembleParams, assembleTunnelParams, computeCardinality, dynamicError, evaluateAsString, evaluateItem, getConstructType, getExpressionName, getImplementationMethod, getInstructionName, getNetCost, getSourceLocator, isXSLT, main, process, toStreamingPattern

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

adoptChildExpression, checkedOperands, checkForUpdatingSubexpressions, clearStreamabilityData, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getCost, getDependencies, getEvaluationMethod, getHostLanguage, getIntegerBounds, getIntrinsicDependencies, getLocation, getObjectName, getPackageData, getParentExpression, getPosture, getPostureAndSweepIfKnown, getProperties, getProperty, getRetainedStaticContext, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStreamability, getSweep, getSystemId, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isCallOnSystemFunction, isIdentical, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, makeStreamingAdjunct, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, optimizeForType, promote, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setFiltered, setFlattened, setLocation, setParentExpression, setPostureAndSweep, setRetainedStaticContext, setRetainedStaticContextLocally, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, toShortString, toString, typeCheckChildren, typeError, unordered

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

GROUP_BY

public static final int GROUP_BY

See Also:

Constant Field Values

GROUP_ADJACENT

public static final int GROUP_ADJACENT

See Also:

Constant Field Values

GROUP_STARTING

public static final int GROUP_STARTING

See Also:

Constant Field Values

GROUP_ENDING

public static final int GROUP_ENDING

See Also:

Constant Field Values

Constructor Detail

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 Detail

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. 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:

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

getKeyItemType

public int getKeyItemType()

Get the primitive item type of the key

Returns:

the primitive item type of the grouping key

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)

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()

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

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

public 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

createsNewNodes

public final boolean createsNewNodes()

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:

createsNewNodes in class Instruction

Returns:

true if the instruction creates new nodes (or if it can't be proved that it doesn't)

promoteChildren

protected void promoteChildren(PromotionOffer offer)
                        throws XPathException

Handle promotion offers, that is, non-local tree rewrites.

Overrides:

promoteChildren in class Instruction

Parameters:

offer - The type of rewrite being offered

Throws:

XPathException

getStreamingAdjunct

public StreamingAdjunct getStreamingAdjunct()

Get a class that supports streamed evaluation of this expression

Overrides:

getStreamingAdjunct in class Expression

Returns:

the relevant StreamingAdjunct, or null if none is available

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

processLeavingTail

public TailCall processLeavingTail(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:

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

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

getAtomicComparer

public AtomicComparer getAtomicComparer(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

map

public SequenceIterator map(XPathContext context)
                     throws XPathException

Map one item to a sequence.

Specified by:

map in interface ContextMappingFunction

Parameters:

context - The processing context. This is supplied only for mapping constructs that set the context node, position, and size. Otherwise it is null.

Returns:

either (a) a SequenceIterator over the sequence of items that the supplied input item maps to, or (b) an Item if it maps to a single item, or (c) null if it maps to an empty sequence.

Throws:

XPathException - if a dynamic error is detected

evaluateSortKey

public AtomicValue evaluateSortKey(int n,
                          XPathContext c)
                            throws XPathException

Callback for evaluating the sort keys

Specified by:

evaluateSortKey in interface SortKeyEvaluator

Throws:

XPathException

getExpressionCompiler

public ExpressionCompiler getExpressionCompiler()

Return the compiler of the ForEachGroup expression

Overrides:

getExpressionCompiler in class Expression

Returns:

the relevant ExpressionCompiler

getSortKeyDefinitionList

public SortKeyDefinitionList getSortKeyDefinitionList()

export

public void export(ExpressionPresenter out)

Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.

Specified by:

export in class Expression

Parameters:

out - the expression presenter used to display the structure

setSelect

public void setSelect(Expression select)

setAction

public void setAction(Expression action)

setKey

public void setKey(Expression key)

setCollationNameExpression

public void setCollationNameExpression(Expression collationNameExpression)

setSortKeyDefinitions

public void setSortKeyDefinitions(SortKeyDefinitionList sortKeyDefinitions)