net.sf.saxon.sort
public class SortExpression extends ComputedExpression
Constructor Summary | |
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SortExpression(Expression select, SortKeyDefinition[] sortKeys) |
Method Summary | |
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int | computeCardinality()
Determine the static cardinality |
int | computeSpecialProperties()
Get the static properties of this expression (other than its type). |
void | display(int level, NamePool pool, PrintStream out) |
ItemType | getItemType(TypeHierarchy th)
Determine the data type of the items returned by the expression, if possible |
boolean | isSortKey(Expression child)
Test whether a given expression is one of the sort keys |
SequenceIterator | iterate(XPathContext context)
Enumerate the results of the expression |
Iterator | iterateSubExpressions()
Get the immediate sub-expressions of this expression. |
Expression | optimize(Optimizer opt, StaticContext env, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
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Expression | promote(PromotionOffer offer)
Offer promotion for this subexpression. |
Expression | simplify(StaticContext env)
Simplify an expression |
Expression | typeCheck(StaticContext env, ItemType contextItemType)
Type-check the expression |
Parameters: th
Returns: a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known in advance)
Returns: an iterator containing the sub-expressions of this expression
This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.
Parameters: opt the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances. env the static context of the expression contextItemType the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to ITEM_TYPE
Returns: the original expression, rewritten if appropriate to optimize execution
Throws: net.sf.saxon.trans.StaticError if an error is discovered during this phase (typically a type error)
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
Returns: if the offer is not accepted, return this expression unchanged. Otherwise return the result of rewriting the expression to promote this subexpression
Throws: net.sf.saxon.trans.XPathException if any error is detected