com.saxonica.extra
Class OptimizerSA

java.lang.Object
  net.sf.saxon.expr.Optimizer
      com.saxonica.extra.OptimizerSA

All Implemented Interfaces:

Serializable

public class OptimizerSA
extends Optimizer

This class doesn't actually do any optimization itself, despite the name. Rather, it is intended to act as a factory for implementation classes that perform optimization, so that the appropriate level of optimization can be selected.

See Also:

Serialized Form

Constructor Summary

OptimizerSA(Configuration config)

Method Summary

Expression	convertPathExpressionToKey(PathExpression pathExp, StaticContext env) 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].
int	isIndexableFilter(Expression filter) Test whether a filter predicate is indexable.
Value	makeClosure(Expression expression, int ref, XPathContext context) Make a Closure, given the expected reference count
BinaryExpression	makeGeneralComparison(Expression p0, int op, Expression p1, boolean backwardsCompatible) Create a GeneralComparison expression
ValueRepresentation	makeIndexedValue(SequenceIterator iter) Create an indexed value
Expression	optimizeCopy(Expression select) Attempt to optimize a copy operation.
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	tryIndexedFilter(FilterExpression f, StaticContext env, boolean indexFirstOperand) Try converting a filter expression to a call on the key function.

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

getConfiguration

Methods inherited from class java.lang.Object

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

Constructor Detail

OptimizerSA

public OptimizerSA(Configuration config)

Method Detail

makeGeneralComparison

public BinaryExpression makeGeneralComparison(Expression p0,
                                              int op,
                                              Expression p1,
                                              boolean backwardsCompatible)

Create a GeneralComparison expression

Overrides:

makeGeneralComparison in class Optimizer

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.

Throws:

XPathException

makeClosure

public Value makeClosure(Expression expression,
                         int ref,
                         XPathContext context)
                  throws XPathException

Make a Closure, given the expected reference count

Overrides:

makeClosure in class Optimizer

Throws:

XPathException

convertPathExpressionToKey

public Expression convertPathExpressionToKey(PathExpression pathExp,
                                             StaticContext env)
                                      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.

Throws:

XPathException

tryIndexedFilter

public Expression tryIndexedFilter(FilterExpression f,
                                   StaticContext env,
                                   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

convertToFilterExpression

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

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

Returns:

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

Throws:

StaticError

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

Throws:

XPathException