com.saxonica.ee.optim

Class IndexedFilterExpression

java.lang.Object

net.sf.saxon.expr.Expression

com.saxonica.ee.optim.IndexedFilterExpression

All Implemented Interfaces:

ExportAgent, Locatable, IdentityComparable

public final class IndexedFilterExpression
extends Expression

An IndexedFilterExpression contains a base expression and a filter predicate. The base expression will always be a local variable reference. The filter will always be a Comparison, and it will have no positional dependencies

Field Summary

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 and Description
IndexedFilterExpression(Expression base, Expression use, Expression search, AtomicComparer comparer, boolean convertUntypedToOther)
IndexedFilterExpression(VariableReference start, ComparisonExpression filter, boolean indexFirstOperand) Constructor

Method Summary

Modifier and Type	Method and Description
PathMap.PathMapNodeSet	addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet) Add a representation of this expression to a PathMap.
int	computeCardinality() Get the static cardinality of this expression
int	computeDependencies() Determine which aspects of the context the expression depends on.
int	computeHashCode() get HashCode for comparing two expressions
int	computeSpecialProperties() Get the static properties of this expression (other than its type).
Expression	copy(RebindingMap rebindings) Copy an expression.
boolean	equals(java.lang.Object other) Is this expression the same as another expression?
void	export(ExpressionPresenter out) Diagnostic print of expression structure.
Expression	getBaseExpression() Get the underlying expression
AtomicComparer	getComparer() Get the comparer used for the comparisons
java.lang.String	getExpressionName() Get a name identifying the kind of expression, in terms meaningful to a user.
int	getImplementationMethod() An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
ItemType	getItemType() Get the data type of the items returned
Expression	getSearchExpression() Get the expression whose value we will be searching for
Expression	getUseExpression() Get the expression to be indexed
boolean	isConvertUntypedToOther() Ask whether untyped atomic values need to be converted to the type of the other operand
SequenceIterator<?>	iterate(XPathContext context) Iterate over the results, returning them in the correct order
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 contextItemType) Perform optimisation of an expression and its subexpressions.
java.lang.String	toShortString() Produce a short string identifying the expression for use in error messages
Expression	typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) Type-check the expression

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

adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeStaticProperties, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getConstructType, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getInterpretedExpression, getIntrinsicDependencies, getLocalRetainedStaticContext, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStaticUType, getStreamerName, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isInstruction, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, process, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, toString, typeCheckChildren, typeError, unordered, verifyParentPointers

Methods inherited from class java.lang.Object

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

Constructor Detail

IndexedFilterExpression

public IndexedFilterExpression(VariableReference start,
                               ComparisonExpression filter,
                               boolean indexFirstOperand)

Constructor

Parameters:

start - Variable containing the sequence of items from which the selection will take place.

filter - An expression defining the filter predicate

indexFirstOperand - true if the first operand of the filter comparison is to be indexed, false if the second operand is to be indexed

IndexedFilterExpression

public IndexedFilterExpression(Expression base,
                               Expression use,
                               Expression search,
                               AtomicComparer comparer,
                               boolean convertUntypedToOther)

Method Detail

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 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.

Overrides:

operands in class Expression

Returns:

an iterator containing the sub-expressions of this expression

getItemType

public ItemType getItemType()

Get the data type of the items returned

Specified by:

getItemType in class Expression

Returns:

an integer representing the data type

getBaseExpression

public Expression getBaseExpression()

Get the underlying expression

Returns:

the expression being filtered

getUseExpression

public Expression getUseExpression()

Get the expression to be indexed

Returns:

the "use" expression, the expression that computes the index key for each item in the population

getSearchExpression

public Expression getSearchExpression()

Get the expression whose value we will be searching for

Returns:

the search expression

isConvertUntypedToOther

public boolean isConvertUntypedToOther()

Ask whether untyped atomic values need to be converted to the type of the other operand

Returns:

true if untyped atomic values are converted; false if they are compared as strings

getComparer

public AtomicComparer getComparer()

Get the comparer used for the comparisons

Returns:

the comparer

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 about the static type of the context item

Returns:

the expression after type-checking (potentially modified to add run-time checks and/or conversions)

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)

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

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

computeCardinality

public int computeCardinality()

Get the static cardinality of this expression

Specified by:

computeCardinality in class Expression

Returns:

the cardinality. The method attempts to determine the case where the filter predicate is guaranteed to select at most one item from the sequence being filtered

computeSpecialProperties

public 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 static properties of the expression, as a bit-significant value

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.

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

equals

public boolean equals(java.lang.Object other)

Is this expression the same as another expression?

Overrides:

equals in class Expression

Parameters:

other - the expression to be compared with this one

Returns:

true if the two expressions are statically equivalent

computeHashCode

public int computeHashCode()

get HashCode for comparing two expressions

Overrides:

computeHashCode in class Expression

Returns:

the hash code

iterate

public SequenceIterator<?> iterate(XPathContext context)
                            throws XPathException

Iterate over the results, returning them in the correct order

Overrides:

iterate in class Expression

Parameters:

context - the dynamic context for the evaluation

Returns:

an iterator over the expression results

Throws:

XPathException - if any dynamic error occurs

computeDependencies

public int computeDependencies()

Determine which aspects of the context the expression depends on. The result is a bitwise-or'ed value composed from constants such as XPathContext.VARIABLES and XPathContext.CURRENT_NODE

Overrides:

computeDependencies in class Expression

Returns:

the dependencies

getExpressionName

public java.lang.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 export() output displaying the 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.

toShortString

public java.lang.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