com.saxonica.extra
Class OptimizerSA

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

All Implemented Interfaces:

java.io.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

Field Summary

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

config

Constructor Summary

OptimizerSA(Configuration config)

Method Summary

ComputedExpression	convertFilterExpressionToKey(FilterExpression f, StaticContext env, Expression doc) Convert a filter expression to a call on the key function.
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.
Closure	makeClosure(Expression expression, int ref) Make a Closure, given the expected reference count
BinaryExpression	makeGeneralComparison(Expression p0, int op, Expression p1, boolean backwardsCompatible) Create a GeneralComparison expression
Expression	optimizeCopy(Expression select) Attempt to optimize a copy operation.
Expression	optimizeSequentialCopy(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.
SequenceIterator	tryIndexedFilter(ValueRepresentation startValue, Expression filter, int isIndexable, XPathContext context)
ComputedExpression	tryToConvertFilterExpressionToKey(FilterExpression f, StaticContext env) 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

clone, equals, finalize, 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

optimizeSequentialCopy

public Expression optimizeSequentialCopy(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 Closure makeClosure(Expression expression,
                           int ref)

Make a Closure, given the expected reference count

Overrides:

makeClosure in class Optimizer

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

tryToConvertFilterExpressionToKey

public ComputedExpression tryToConvertFilterExpressionToKey(FilterExpression f,
                                                            StaticContext env)
                                                     throws XPathException

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

Overrides:

tryToConvertFilterExpressionToKey in class Optimizer

Throws:

XPathException

convertFilterExpressionToKey

public ComputedExpression convertFilterExpressionToKey(FilterExpression f,
                                                       StaticContext env,
                                                       Expression doc)
                                                throws XPathException

Convert a filter expression to a call on the key function. Return null if not possible

Throws:

XPathException

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

tryIndexedFilter

public SequenceIterator tryIndexedFilter(ValueRepresentation startValue,
                                         Expression filter,
                                         int isIndexable,
                                         XPathContext context)
                                  throws XPathException

Overrides:

tryIndexedFilter in class Optimizer

Throws:

XPathException