com.saxonica.expr.ee
Class OptimizerEE

java.lang.Object
  net.sf.saxon.expr.Optimizer
      com.saxonica.expr.ee.OptimizerEE

All Implemented Interfaces:

Serializable

public class OptimizerEE
extends Optimizer

This class performs a number of optimizations that are specific to the Saxon-EE product. The relevant methods override dummy methods (that generally perform no optimization) in the superclass, which is used by Saxon-HE.

See Also:

Serialized Form

Field Summary

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

config, FULL_OPTIMIZATION, NO_OPTIMIZATION

Constructor Summary

OptimizerEE(Configuration config)
Create the Saxon-EE optimizer

Method Summary

Expression	convertPathExpressionToKey(PathExpression pathExp, ExpressionVisitor visitor) Examine a path expression to see whether it can be replaced by a call on the key() function; if so, generate an appropriate key definition and return the call on key().
FilterExpression	convertToFilterExpression(PathExpression pathExp, TypeHierarchy th) Convert a path expression such as a/b/c[predicate] into a filter expression of the form (a/b/c)[predicate].
Expression	extractGlobalVariables(Expression body, ExpressionVisitor visitor, PromotionOffer offer) Extract subexpressions from the body of a function that can be evaluated as global variables
Expression	generateMultithreadedInstruction(Expression instruction) Generate a multi-threaded version of an instruction.
int	isIndexableFilter(Expression filter) Test whether a filter predicate is indexable.
Expression	makeConditionalDocumentSorter(DocumentSorter sorter, PathExpression path) Make a conditional document sorter.
void	makeCopyOperationsExplicit(Expression parent, Expression child) In streaming mode, make the copy operation applied to subexpressions of a complex-content sequence constructor into explicit copy-of operations.
ValueRepresentation	makeIndexedValue(SequenceIterator iter) Create an indexed value
RuleTarget	makeInversion(Pattern pattern, Template template, NodeTest nodeTest) Generate the inversion of the expression comprising the body of a template rules.
Expression	makeStreamingApplyTemplates(ApplyTemplates inst) Make a streaming applyTemplates instruction.
Pattern	makeStreamingPattern(Expression exp, List<String> reasonForFailure) Convert an expression that is capable of being evaluated as a filter on an XML event stream into a Selection object which is able to act as the filter
Expression	optimizeCopy(Expression select) Attempt to optimize a copy operation.
Expression	optimizeForExpressionForStreaming(ForExpression expr) In streaming mode, optimizer a ForExpression for streaming.
Expression	optimizeQuantifiedExpressionForStreaming(QuantifiedExpression expr) In streaming mode, optimize a QuantifiedExpression for streaming.
Expression	optimizeStreamingCopy(Expression select) Given a select expression, determine whether it is a candidate for sequential processing, and if so, return a SequentialCopy expression that does the work.
Expression	promoteExpressionsToGlobal(Expression body, ExpressionVisitor visitor) Identify expressions within a function or template body that can be promoted to be evaluated as global variables.
BinaryExpression	simplifyGeneralComparison(GeneralComparison gc, boolean backwardsCompatible) Simplify a GeneralComparison expression
Expression	tryIndexedFilter(FilterExpression f, ExpressionVisitor visitor, boolean indexFirstOperand) Try converting a filter expression to a call on the key function.
Expression	tryInlineFunctionCall(UserFunctionCall functionCall, ExpressionVisitor visitor, ItemType contextItemType) Replace a function call by the body of the function, assuming all conditions for inlining the function are satisfied
Expression	trySwitch(Choose choose, StaticContext env) Try to convert a Choose expression (or an XQuery 1.1 switch) into an optimized switch

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

getConfiguration, getOptimizationLevel, isVariableReplaceableByDot, setOptimizationLevel, trace, trace

Methods inherited from class java.lang.Object

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

Constructor Detail

OptimizerEE

public OptimizerEE(Configuration config)

Create the Saxon-EE optimizer

Parameters:

config - the Saxon-EE configuration

Method Detail

simplifyGeneralComparison

public BinaryExpression simplifyGeneralComparison(GeneralComparison gc,
                                                  boolean backwardsCompatible)

Simplify a GeneralComparison expression

Overrides:

simplifyGeneralComparison in class Optimizer

Parameters:

gc - the GeneralComparison to be simplified

backwardsCompatible - true if in 1.0 compatibility mode

Returns:

the simplified expression

optimizeCopy

public Expression optimizeCopy(Expression select)
                        throws XPathException

Attempt to optimize a copy operation. Return null if no optimization is possible.

Overrides:

optimizeCopy in class Optimizer

Parameters:

select - the expression that selects the items to be copied

Returns:

null if no optimization is possible, or an expression that does an optimized copy of these items otherwise

Throws:

XPathException

optimizeStreamingCopy

public Expression optimizeStreamingCopy(Expression select)
                                 throws XPathException

Given a select expression, determine whether it is a candidate for sequential processing, and if so, return a SequentialCopy expression that does the work.

To qualify, the select expression must be a path expression that starts with a call on doc() or document(), and whose subsequent steps are all axis steps using the child, descendant, and attribute axes only; there must be no predicates; it must match either elements only, or attributes only

Parameters:

select - the select expression to be examined

Returns:

either null if no optimization is possible, or a StreamingCopy expression

Throws:

XPathException

makeCopyOperationsExplicit

public void makeCopyOperationsExplicit(Expression parent,
                                       Expression child)
                                throws XPathException

In streaming mode, make the copy operation applied to subexpressions of a complex-content sequence constructor into explicit copy-of operations. This makes constructs such as ]]> streamable, by using the same run-time logic as if xsl:copy-of had been used.

Overrides:

makeCopyOperationsExplicit in class Optimizer

Parameters:

parent - The parent expression of the expression that is to be wrapped in an implicit copy-of.

child - The expression that is to be wrapped in an implicit copy-of, if it is suitable.

Throws:

XPathException

optimizeForExpressionForStreaming

public Expression optimizeForExpressionForStreaming(ForExpression expr)
                                             throws XPathException

In streaming mode, optimizer a ForExpression for streaming. This is possible if the "in" part of the for expression does a downward selection of the streamed input, while the "return" part does not access the streamed input at all (specifically, if it has no dependencies on the context node). The expression is converted to streamable form by rewriting "for $t in S return f($t)" as "for-each S return f(.)". This depends on the generated for-each expression being streamable, which will not always be the case, for example if the return expression makes two downward selections from the range variable, or a non-downward selection.

Overrides:

optimizeForExpressionForStreaming in class Optimizer

Parameters:

expr - the expression to be optimized

Returns:

the optimized expression, or the original expression if no optimization was possible.

Throws:

XPathException

optimizeQuantifiedExpressionForStreaming

public Expression optimizeQuantifiedExpressionForStreaming(QuantifiedExpression expr)
                                                    throws XPathException

In streaming mode, optimize a QuantifiedExpression for streaming. This is possible if the "select" part of the quantified expression does a downward selection of the streamed input, while the "satisfies" part does not access the streamed input at all (specifically, if it has no dependencies on the context node). The expression is converted to streamable form by rewriting "some $t in S satisfies f($t)" as "exists(for-each S return boolean(f(.)[.])", and likewise mutatis mutandis for "every $t....". This depends on the generated for-each expression being streamable, which will not always be the case, for example if the satisfies expression makes two downward selections from the range variable, or a non-downward selection.

Overrides:

optimizeQuantifiedExpressionForStreaming in class Optimizer

Parameters:

expr - the expression to be optimized

Returns:

the optimized expression, or the original expression if no optimization was possible.

Throws:

XPathException

makeStreamingPattern

public Pattern makeStreamingPattern(Expression exp,
                                    List<String> reasonForFailure)

Convert an expression that is capable of being evaluated as a filter on an XML event stream into a Selection object which is able to act as the filter

Parameters:

exp - the expression to be converted

reasonForFailure - a list which will be populated with messages giving reasons why the expression cannot be converted

Returns:

the Selection object if conversion succeeds; otherwise null

Throws:

XPathException

convertPathExpressionToKey

public Expression convertPathExpressionToKey(PathExpression pathExp,
                                             ExpressionVisitor visitor)
                                      throws XPathException

Examine a path expression to see whether it can be replaced by a call on the key() function; if so, generate an appropriate key definition and return the call on key(). If not, return null.

Overrides:

convertPathExpressionToKey in class Optimizer

Parameters:

pathExp - The path expression to be converted.

visitor - The expression visitor

Returns:

the optimized expression, or null if no optimization is possible

Throws:

XPathException

tryIndexedFilter

public Expression tryIndexedFilter(FilterExpression f,
                                   ExpressionVisitor visitor,
                                   boolean indexFirstOperand)

Try converting a filter expression to a call on the key function. Return the supplied expression unchanged if not possible

Overrides:

tryIndexedFilter in class Optimizer

Parameters:

f - the filter expression to be converted

visitor - the expression visitor, which must be currently visiting the filter expression f

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

Returns:

the optimized expression, or the unchanged expression f if no optimization is possible

convertToFilterExpression

public FilterExpression convertToFilterExpression(PathExpression pathExp,
                                                  TypeHierarchy th)
                                           throws XPathException

Convert a path expression such as a/b/c[predicate] into a filter expression of the form (a/b/c)[predicate]. This is possible whenever the predicate is non-positional. The conversion is useful in the case where the path expression appears inside a loop, where the predicate depends on the loop variable but a/b/c does not.

Overrides:

convertToFilterExpression in class Optimizer

Parameters:

pathExp - the path expression to be converted

th - the type hierarchy cache

Returns:

the resulting filterexpression if conversion is possible, or null if not

Throws:

XPathException

isIndexableFilter

public int isIndexableFilter(Expression filter)

Test whether a filter predicate is indexable.

Overrides:

isIndexableFilter in class Optimizer

Parameters:

filter - the predicate expression

Returns:

0 if not indexable; +1 if the predicate is in the form expression=value; -1 if it is in the form value=expression

makeIndexedValue

public ValueRepresentation makeIndexedValue(SequenceIterator iter)
                                     throws XPathException

Create an indexed value

Overrides:

makeIndexedValue in class Optimizer

Parameters:

iter - the iterator that delivers the sequence of values to be indexed

Returns:

the indexed value

Throws:

XPathException

makeConditionalDocumentSorter

public Expression makeConditionalDocumentSorter(DocumentSorter sorter,
                                                PathExpression path)

Make a conditional document sorter. This optimization is attempted when a DocumentSorter is wrapped around a path expression

Overrides:

makeConditionalDocumentSorter in class Optimizer

Parameters:

sorter - an expression that sorts and deduplicates its operand

path - the path expression that is the operand of the sorter

Returns:

either the original sorter, if no optimization is possible; or a ConditionalSorter which first tests a condition, and performs the sort if the condition is true, or returns the unsorted operand if not. In practice the condition is always a test whether the first item in the path expression contains more than one item

tryInlineFunctionCall

public Expression tryInlineFunctionCall(UserFunctionCall functionCall,
                                        ExpressionVisitor visitor,
                                        ItemType contextItemType)

Replace a function call by the body of the function, assuming all conditions for inlining the function are satisfied

Overrides:

tryInlineFunctionCall in class Optimizer

Parameters:

functionCall - the functionCall expression

visitor - the expression visitor

contextItemType - the static type of the context item

Returns:

either the original expression unchanged, or an expression that consists of the inlined function body, with all function parameters bound as required.

promoteExpressionsToGlobal

public Expression promoteExpressionsToGlobal(Expression body,
                                             ExpressionVisitor visitor)
                                      throws XPathException

Identify expressions within a function or template body that can be promoted to be evaluated as global variables.

Overrides:

promoteExpressionsToGlobal in class Optimizer

Parameters:

body - the body of the template or function

visitor - the expression visitor

Returns:

the expression after subexpressions have been promoted to global variables

Throws:

XPathException

trySwitch

public Expression trySwitch(Choose choose,
                            StaticContext env)

Try to convert a Choose expression (or an XQuery 1.1 switch) into an optimized switch

Overrides:

trySwitch in class Optimizer

Parameters:

choose - the Choose expression

env - the static context

Returns:

the result of optimizing this (the original expression if no optimization was possible)

extractGlobalVariables

public Expression extractGlobalVariables(Expression body,
                                         ExpressionVisitor visitor,
                                         PromotionOffer offer)
                                  throws XPathException

Extract subexpressions from the body of a function that can be evaluated as global variables

Overrides:

extractGlobalVariables in class Optimizer

Parameters:

body - an expression with no dependencies other than on global variables (already checked by the caller)

offer - The PromotionOffer. Will be marked to indicate whether any action was taken

Returns:

a reference to the new global variable if a variable has been created, or null if not

Throws:

XPathException

makeStreamingApplyTemplates

public Expression makeStreamingApplyTemplates(ApplyTemplates inst)
                                       throws XPathException

Make a streaming applyTemplates instruction. Supported in Saxon-EE only

Overrides:

makeStreamingApplyTemplates in class Optimizer

Parameters:

inst - the unoptimized applyTemplates instruction

Throws:

XPathException

makeInversion

public RuleTarget makeInversion(Pattern pattern,
                                Template template,
                                NodeTest nodeTest)
                         throws XPathException

Generate the inversion of the expression comprising the body of a template rules. Supported in Saxon-EE only

Overrides:

makeInversion in class Optimizer

Parameters:

pattern - the match pattern of this template rule

template - the template to be inverted

nodeTest - the static item type of the context node of the template

Throws:

XPathException

generateMultithreadedInstruction

public Expression generateMultithreadedInstruction(Expression instruction)

Generate a multi-threaded version of an instruction. Supported in Saxon-EE only; ignored with no action in Saxon-HE and Saxon-PE

Overrides:

generateMultithreadedInstruction in class Optimizer

Parameters:

instruction - the instruction to be multi-threaded

Returns:

the multi-threaded version of the instruction