net.sf.saxon.pattern

Class KeyPattern

public final class KeyPattern extends Pattern

A KeyPattern is a pattern of the form key(keyname, keyvalue)
Constructor Summary
KeyPattern(int namecode, Expression key)
Constructor
Method Summary
Patternanalyze(StaticContext env, ItemType contextItemType)
Type-check the pattern.
intgetDependencies()
Get the dependencies of the pattern.
NodeTestgetNodeTest()
Get a NodeTest that all the nodes matching this pattern must satisfy
IteratoriterateSubExpressions()
Iterate over the subexpressions within this pattern
booleanmatches(NodeInfo e, XPathContext context)
Determine whether this Pattern matches the given Node.
voidpromote(PromotionOffer offer)
Offer promotion for subexpressions within this pattern.

Constructor Detail

KeyPattern

public KeyPattern(int namecode, Expression key)
Constructor

Parameters: namecode the name of the key key the value of the key: either a StringValue or a VariableReference

Method Detail

analyze

public Pattern analyze(StaticContext env, ItemType contextItemType)
Type-check the pattern. This is needed for patterns that contain variable references or function calls.

Returns: the optimised Pattern

getDependencies

public int getDependencies()
Get the dependencies of the pattern. The only possible dependency for a pattern is on local variables. This is analyzed in those patterns where local variables may appear.

getNodeTest

public NodeTest getNodeTest()
Get a NodeTest that all the nodes matching this pattern must satisfy

iterateSubExpressions

public Iterator iterateSubExpressions()
Iterate over the subexpressions within this pattern

matches

public boolean matches(NodeInfo e, XPathContext context)
Determine whether this Pattern matches the given Node.

Parameters: e The NodeInfo representing the Element or other node to be tested against the Pattern

Returns: true if the node matches the Pattern, false otherwise

promote

public void promote(PromotionOffer offer)
Offer promotion for subexpressions within this pattern. The offer will be accepted if the subexpression is not dependent on the factors (e.g. the context item) identified in the PromotionOffer. By default the offer is not accepted - this is appropriate in the case of simple expressions such as constant values and variable references where promotion would give no performance advantage. This method is always called at compile time.

Unlike the corresponding method on Expression, this method does not return anything: it can make internal changes to the pattern, but cannot return a different pattern. Only certain kinds of promotion are applicable within a pattern: specifically, promotions affecting local variable references within the pattern.

Parameters: offer details of the offer, for example the offer to move expressions that don't depend on the context to an outer level in the containing expression

Throws: net.sf.saxon.trans.XPathException if any error is detected