## 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

Copyright (c) 2004-2010 Saxonica Limited. All rights reserved.