| java.lang.Object
 net.sf.saxon.expr.PromotionOffer
| PromotionOffer | | public class PromotionOffer (Code) | | PromotionOffer is an object used transiently during compilation of an expression. It contains
information passed by a containing expression to its subexpressions, when looking for subexpressions
that can be promoted to a higher level because they are not dependent on the context established
by the containing expression. The object is also used to pass back return information when the
promotion actually takes place.
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| Field Summary | |
| final public static int | FOCUS_INDEPENDENT
FOCUS_INDEPENDENT requests promotion of all non-trivial subexpressions that don't depend on the
focus. | | final public static int | INLINE_VARIABLE_REFERENCES
Inline variable references causes all references to a variable V to be replaced by the
expression E. | | final public static int | RANGE_INDEPENDENT
RANGE_INDEPENDENT requests promotion of all non-trivial subexpressions that don't depend on a
specified range variable. | | final public static int | REPLACE_CURRENT
REPLACE_CURRENT causes calls to the XSLT current() function to be replaced by
reference to a variable. | | final public static int | UNORDERED
UNORDERED indicates that the containing expression does not require the results
to be delivered in any particular order. | | public boolean | accepted
| | public int | action
| | public Binding[] | bindingList
In the case of RANGE_INDEPENDENT and WHERE_CLAUSE, "binding" identifies the range variables whose dependencies
we are looking for. | | public Expression | containingExpression
When a promotion offer is made, containingExpression identifies the level to which the promotion
should occur. | | public boolean | mustEliminateDuplicates
In the case of UNORDERED, "mustEliminateDuplicates" is a boolean that is set to
true if the nodes can be delivered in any order so long as there are no duplicates
(for example, as required by the count() function). | | public boolean | promoteDocumentDependent
In the case of FOCUS_INDEPENDENT, "promoteDocumentDependent" is a boolean that, when set to
true, indicates that it is safe to promote a subexpression that depends on the context document
but not on other aspects of the focus. | | public boolean | promoteXSLTFunctions
In the case of FOCUS_INDEPENDENT, "promoteXSLTFunctions" is a boolean that, when set to true, indicates
that it is safe to promote XSLT functions such as current(). |
| Method Summary | |
| public Expression | accept(Expression child)
Method to test whether a subexpression qualifies for promotion, and if so, to
accept the promotion.
if promotion was done, returns the expression that should be used in placeof the child expression. | | public Optimizer | getOptimizer()
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| FOCUS_INDEPENDENT | | final public static int FOCUS_INDEPENDENT(Code) | | FOCUS_INDEPENDENT requests promotion of all non-trivial subexpressions that don't depend on the
focus. This is typically used to extract subexpressions from a filter predicate. The offer is
optional - each subexpression can decide whether it's worth the trouble of promoting itself.
The offer is normally passed on to subexpressions, except subexpressions that are evaluated
with a different focus
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| INLINE_VARIABLE_REFERENCES | | final public static int INLINE_VARIABLE_REFERENCES(Code) | | Inline variable references causes all references to a variable V to be replaced by the
expression E. The variable is supplied in the "binding" property; the replacement expression
in the containingExpression property. A special case is where the replacement expression is
a ContextItemExpression; in this case the offer is not passed on to subexpressions where
the context is different.
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| RANGE_INDEPENDENT | | final public static int RANGE_INDEPENDENT(Code) | | RANGE_INDEPENDENT requests promotion of all non-trivial subexpressions that don't depend on a
specified range variable. This is typically used to extract subexpressions from the action of
a for expression or the condition of a some/every quantified expression. The offer is
optional - each subexpression can decide whether it's worth the trouble of promoting itself.
The offer is normally passed on to subexpressions, except subexpressions that are evaluated
with a different focus or a different range variable, because these may have other dependencies
that prevent their promotion.
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| REPLACE_CURRENT | | final public static int REPLACE_CURRENT(Code) | | REPLACE_CURRENT causes calls to the XSLT current() function to be replaced by
reference to a variable. The variable binding is the single member of the array bindingList
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| UNORDERED | | final public static int UNORDERED(Code) | | UNORDERED indicates that the containing expression does not require the results
to be delivered in any particular order. The boolean mustEliminateDuplicates
is set if duplicate items in the result are not allowed.
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| accepted | | public boolean accepted(Code) | | Flag that is set if the offer has been accepted, that is, if the expression has changed
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| action | | public int action(Code) | | action is one of the possible promotion actions, FOCUS_INDEPENDENT, RANGE_INDEPENDENT,
INLINE_VARIABLE_REFERENCES, ANY_ORDER, ANY_ORDER_UNIQUE
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| bindingList | | public Binding[] bindingList(Code) | | In the case of RANGE_INDEPENDENT and WHERE_CLAUSE, "binding" identifies the range variables whose dependencies
we are looking for. For INLINE_VARIABLE_REFERENCES it is a single Binding that we are aiming to inline
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| containingExpression | | public Expression containingExpression(Code) | | When a promotion offer is made, containingExpression identifies the level to which the promotion
should occur. When a subexpression is promoted, an expression of the form let $VAR := SUB return ORIG
is created, and this replaces the original containingExpression within the PromotionOffer.
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| mustEliminateDuplicates | | public boolean mustEliminateDuplicates(Code) | | In the case of UNORDERED, "mustEliminateDuplicates" is a boolean that is set to
true if the nodes can be delivered in any order so long as there are no duplicates
(for example, as required by the count() function). If this boolean is false, the
nodes can be delivered in any order and duplicates are allowed (for example, as
required by the boolean() function).
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| promoteDocumentDependent | | public boolean promoteDocumentDependent(Code) | | In the case of FOCUS_INDEPENDENT, "promoteDocumentDependent" is a boolean that, when set to
true, indicates that it is safe to promote a subexpression that depends on the context document
but not on other aspects of the focus. This is the case, for example, in a filter expression when
it is known that all the nodes selected by the expression will be in the same document - as happens
when the filter is applied to a path expression. This allows subexpressions such as key() to be
promoted
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| promoteXSLTFunctions | | public boolean promoteXSLTFunctions(Code) | | In the case of FOCUS_INDEPENDENT, "promoteXSLTFunctions" is a boolean that, when set to true, indicates
that it is safe to promote XSLT functions such as current(). This flag is set when rewriting XPath expressions
and is unset when rewriting XSLT templates.
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| PromotionOffer | | public PromotionOffer(Optimizer optimizer)(Code) | | Create a PromotionOffer for use with a particular Optimizer
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| accept | | public Expression accept(Expression child) throws XPathException(Code) | | Method to test whether a subexpression qualifies for promotion, and if so, to
accept the promotion.
if promotion was done, returns the expression that should be used in placeof the child expression. If no promotion was done, returns null. |
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