Package 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.

  • Constructor Details

    • OptimizerEE

      public OptimizerEE(Configuration config)
      Create the Saxon-EE optimizer
      Parameters:
      config - the Saxon-EE configuration

  • Method Details

    • optimizeValueComparison

      public Expression optimizeValueComparison(ValueComparison vc, ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException
      Optimize a value comparison
      Overrides:
      optimizeValueComparison in class Optimizer
      Parameters:
      vc - the value comparison expression
      visitor - the expression visitor
      contextInfo - static context item information
      Returns:
      either the original value comparison, or an optimized equivalent
      Throws:
      XPathException - if things go wrong

    • 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
      contextItemType - the static type of the context item
      Returns:
      the simplified expression

    • optimizeSaxonStreamFunction

      public Expression optimizeSaxonStreamFunction(ExpressionVisitor visitor, ContextItemStaticInfo cisi, Expression select) throws XPathException
      Attempt to optimize a copy operation. Return null if no optimization is possible.
      Overrides:
      optimizeSaxonStreamFunction in class Optimizer
      Parameters:
      visitor - the expression visitor
      cisi - Static information about the context item
      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 - if any error occurs

    • makeCopyOperationsExplicit

      public 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. This makes constructs such as <e><xsl:sequence select="y"/></e> 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.

    • 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)
      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.

    • 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 - if any error occurs

    • convertPathExpressionToKey

      public 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(). 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

    • 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

    • reorderPredicates

      public FilterExpression reorderPredicates(FilterExpression f, ExpressionVisitor visitor, ContextItemStaticInfo cisi) throws XPathException
      Consider reordering the predicates in a filter expression based on cost estimates and other criteria
      Overrides:
      reorderPredicates in class Optimizer
      Parameters:
      f - the filter expression
      visitor - expression visitor
      cisi - information about the context item type
      Returns:
      either the original expression, or an optimized replacement
      Throws:
      XPathException - if things go wrong

    • convertToFilterExpression

      public 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]. 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

    • 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 GroundedValue 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 - if an error occurs

    • optimizeNodeSetPattern

      public void optimizeNodeSetPattern(NodeSetPattern pattern)
      Overrides:
      optimizeNodeSetPattern in class Optimizer

    • prepareForStreaming

      public void prepareForStreaming(Expression exp) throws XPathException
      Prepare an expression for streaming
      Overrides:
      prepareForStreaming in class Optimizer
      Parameters:
      exp - the expression to be prepared
      Throws:
      XPathException - if any error occurs

    • evaluateStreamingArgument

      public Sequence evaluateStreamingArgument(Expression expr, XPathContext context) throws XPathException
      Evaluate the streaming (first) argument of a streamable stylesheet function
      Overrides:
      evaluateStreamingArgument in class Optimizer
      Parameters:
      expr - the expression supplied for the value of the streaming argument
      context - the XPath evaluation context of the caller
      Returns:
      the (nominal) result of the evaluation
      Throws:
      XPathException - if any error occurs

    • makeConditionalDocumentSorter

      public Expression makeConditionalDocumentSorter(DocumentSorter sorter, SlashExpression 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 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

    • 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, ExpressionVisitor visitor)
      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
      visitor - the expression visitor
      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)
      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

    • 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 - if any error occurs

    • promoteExpressionsToGlobal

      public Expression promoteExpressionsToGlobal(Expression expr, 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:
      expr - the expression; either this expression or any subexpression might be promoted
      globalVariableManager - the global variable manager
      visitor - the expression visitor
      Returns:
      the expression after subexpressions have been promoted to global variables; or null if no action was taken
      Throws:
      XPathException - if any error occurs

    • eliminateCommonSubexpressions

      public Expression eliminateCommonSubexpressions(Expression in)
      Description copied from class: Optimizer
      Eliminate common subexpressions. Rewrites (contains(X, 'x') and contains(X, 'y')) as (let $vv:C := X return (contains($vv:C, 'x') and contains($vv:C, 'y'))). Dummy method; the optimization happens only in Saxon-EE.
      Overrides:
      eliminateCommonSubexpressions in class Optimizer
      Parameters:
      in - the expression to be optimized
      Returns:
      out the optimized expression (possibly the same as the input).

    • 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

    • optimizeNumberInstruction

      public Expression optimizeNumberInstruction(NumberInstruction ni, ContextItemStaticInfo contextInfo)
      Overrides:
      optimizeNumberInstruction in class Optimizer

    • assessFunctionStreamability

      public void assessFunctionStreamability(XSLFunction sourceFunction, UserFunction compiledFunction)
      Assess whether a declared-streamable function is actually streamable. This analysis takes no account of the actual function call, which is assessed later in the streaming adjunct for the UserFunctioncall class
      Overrides:
      assessFunctionStreamability in class Optimizer