public class MultiIndex extends java.lang.Object
A MultiIndex handles a single "use" expression, for a single population.
The class is used to support indexes over the value of a variable, as determined by the Saxon-EE optimizer.
The class supports two kinds of equality matching. In ConvertUntypedToOther mode, corresponding to the XPath "=" operator, an untyped value is converted to the type of the other item, so the double 5e0 will match the untypedAtomic value "5". In ConvertUntypedToString mode, untyped atomic values are always converted to strings: this corresponds to the XPath "eq" operator (and to the rules for xsl:key).
Each MultiIndex index is in fact a set of sub-indexes, one for each primitive type encountered. In an expression such as $seq[./A = $B], one sub-index is built for each primitive type that occurs in the sequence $B. In this index, any untyped atomic values in ./A are converted to that primitive type. For an expression such as $seq[./A eq $B], a single index is built, in which untyped atomic values in ./A are converted to strings.
A particular difficulty arises where $B (in the expression $seq[./A eq $B]) is untypedAtomic. In this situation an index is built in which any untypedAtomic values in ./A are indexed as strings. While building the index, we note all the primitive types that occur in ./A, and then we convert the search term $B to each of these types in turn before doing the index lookup. In practice, of course, it is very rare for the index to be heterogeneous.
|Modifier and Type||Class and Description|
Iterator over a subset of the items in this IndexedValue, identified by an IntSet holding the positions of the items in the selected subset (zero-based)
|Constructor and Description|
Create a MultiIndex
|Modifier and Type||Method and Description|
Retrieve items that match a given index value
public MultiIndex(GroundedValue indexedValue)
indexedValue- the sequence to be indexed
public SequenceIterator findItems(Expression use, SequenceIterator values, boolean convertUntypedToOther, boolean firstOnly, StringCollator collator, XPathContext context) throws XPathException
use- the expression whose value is to be matched
values- the set of values to be found
convertUntypedToOther- true if untypedAtomic values are to be converted to the type of the other operand
firstOnly- true if only the first matching value is needed
collator- StringCollator used to compare values for equality (encapsulates a collation if necessary)
context- the dynamic evaluation context
XPathException- if a failure occurs
Copyright (c) 2004-2022 Saxonica Limited. All rights reserved.