com.saxonica.ee.optim

Class OptimizerEE

java.lang.Object

net.sf.saxon.expr.parser.Optimizer

com.saxonica.ee.optim.OptimizerEE

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.

Field Summary

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

config, FULL_OPTIMIZATION, NO_OPTIMIZATION

Constructor Summary

Constructors

Constructor and Description
OptimizerEE(Configuration config) Create the Saxon-EE optimizer

Method Summary

Methods

Modifier and Type	Method and Description
void	checkStreamability(XSLTemplate sourceTemplate, TemplateRule compiledTemplate) Check the streamability of a template
Expression	compileToByteCode(Expression expr, String objectName, int evaluationMethods) Generate Java byte code for an expression
Expression	convertPathExpressionToKey(SlashExpression 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(SlashExpression 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
int	gatherOrExpressions(int commonParts, ExpressionVisitor visitor, ContextItemStaticInfo contextItemType, HashMap<Expression,List<Expression>> map, List<Expression> otherExps, Expression expr) Try to convert a collection of comparisons connected by "or" operators into a single GeneralComparison
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, SlashExpression path) Make a conditional document sorter.
void	makeCopyOperationsExplicit(Expression parent, Operand childOp) In streaming mode, make the copy operation applied to subexpressions of a complex-content sequence constructor into explicit copy-of operations.
Sequence	makeIndexedValue(SequenceIterator iter) Create an indexed value
Expression	optimizeCopy(Expression select) Attempt to optimize a copy operation.
Expression	optimizeForExpressionForStreaming(ForExpression expr) In streaming mode, optimize a ForExpression for streaming.
Expression	optimizeGeneralComparison(ExpressionVisitor visitor, GeneralComparison gc, boolean backwardsCompatible, ContextItemStaticInfo contextItemType) Optimize a GeneralComparison expression.
Expression	optimizeQuantifiedExpressionForStreaming(QuantifiedExpression expr) In streaming mode, optimize a QuantifiedExpression for streaming.
Expression	promoteExpressionsToGlobal(Expression body, GlobalVariableManager globalVariableManager, ExpressionVisitor visitor) Identify expressions within a function or template body that can be promoted to be evaluated as global variables.
Expression	tryGeneralComparison(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType, OrExpression orExpr) Try to convert an Or expression into a comparison with Literal sequence
Expression	tryIndexedFilter(FilterExpression f, ExpressionVisitor visitor, boolean indexFirstOperand, boolean contextIsDoc) Try converting a filter expression to a call on the key function.
Expression	tryInlineFunctionCall(UserFunctionCall functionCall, ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) Replace a function call by the body of the function, assuming all conditions for inlining the function are satisfied
Expression	trySwitch(Choose choose) Try to convert a Choose expression (or an XQuery 3.0 switch) into an optimized switch

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

getConfiguration, getOptimizationLevel, isVariableReplaceableByDot, makeInversion, 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

optimizeGeneralComparison

public Expression optimizeGeneralComparison(ExpressionVisitor visitor,
                                   GeneralComparison gc,
                                   boolean backwardsCompatible,
                                   ContextItemStaticInfo contextItemType)

Optimize a GeneralComparison expression. Saxon-EE has a number of strategies for handling these; for example when comparing against a constant set of values, the expression is turned into a call on map:contains().

Overrides:

optimizeGeneralComparison in class Optimizer

Parameters:

visitor - the expression visitor

gc - the GeneralComparison to be optimized

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

makeCopyOperationsExplicit

public void makeCopyOperationsExplicit(Expression parent,
                              Operand childOp)
                                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.

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

Throws:

XPathException

checkStreamability

public void checkStreamability(XSLTemplate sourceTemplate,
                      TemplateRule compiledTemplate)
                        throws XPathException

Check the streamability of a template

Overrides:

checkStreamability in class Optimizer

Parameters:

sourceTemplate - the source of the template in the stylesheet tree

compiledTemplate - the compiled template

Throws:

XPathException - if the template is declared streamable but does not satisfy the straming rules

optimizeForExpressionForStreaming

public Expression optimizeForExpressionForStreaming(ForExpression expr)
                                             throws XPathException

In streaming mode, optimize 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

convertPathExpressionToKey

public Expression convertPathExpressionToKey(SlashExpression 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,
                          boolean contextIsDoc)

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;

contextIsDoc - true if the context item is known to be a document node

Returns:

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

convertToFilterExpression

public FilterExpression convertToFilterExpression(SlashExpression 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 Sequence 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,
                                       SlashExpression path)
                                         throws XPathException

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 slash 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

Throws:

XPathException

tryInlineFunctionCall

public Expression tryInlineFunctionCall(UserFunctionCall functionCall,
                               ExpressionVisitor visitor,
                               ContextItemStaticInfo 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.

trySwitch

public Expression trySwitch(Choose choose)

Try to convert a Choose expression (or an XQuery 3.0 switch) into an optimized switch

Overrides:

trySwitch in class Optimizer

Parameters:

choose - the Choose expression

Returns:

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

gatherOrExpressions

public int gatherOrExpressions(int commonParts,
                      ExpressionVisitor visitor,
                      ContextItemStaticInfo contextItemType,
                      HashMap<Expression,List<Expression>> map,
                      List<Expression> otherExps,
                      Expression expr)
                        throws XPathException

Try to convert a collection of comparisons connected by "or" operators into a single GeneralComparison

Parameters:

commonParts - the number of common subexpressions found at this level

visitor - the expression visitor

contextItemType - static information about the context item type

map - a map to be populated with comparison expressions, keyed on the common operand

otherExps - a list to be populated with expressions in the "or" tree that are not comparison expressions, so they are retained "as is"

expr - the Or expression to be optimized

Returns:

a tally of the common expressions so far

Throws:

XPathException - if an error occurs

tryGeneralComparison

public Expression tryGeneralComparison(ExpressionVisitor visitor,
                              ContextItemStaticInfo contextItemType,
                              OrExpression orExpr)
                                throws XPathException

Try to convert an Or expression into a comparison with Literal sequence

Overrides:

tryGeneralComparison in class Optimizer

Parameters:

visitor - the expression visitor

contextItemType - static information about the context item type

orExpr - the Choose expression

Returns:

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

Throws:

XPathException

promoteExpressionsToGlobal

public Expression promoteExpressionsToGlobal(Expression body,
                                    GlobalVariableManager globalVariableManager,
                                    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

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

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

compileToByteCode

public Expression compileToByteCode(Expression expr,
                           String objectName,
                           int evaluationMethods)

Generate Java byte code for an expression

Overrides:

compileToByteCode in class Optimizer

Parameters:

expr - the expression to be compiled

objectName - the name of the object to be compiled, used as a hint for the Java class/method name

evaluationMethods - The evaluation modes for which code is generated. Currently a subset of Expression.PROCESS_METHOD, Expression.ITERATE_METHOD. If no code is generated for a given evaluation method, the fallback implementation from the superclass is used.

Returns:

the compiled expression if possible, or null if compilation is not possible