public final class CollationKeyFilter extends TokenFilter
Converts each token into its CollationKey, and then
encodes the CollationKey with IndexableBinaryStringTools, to allow
it to be stored as an index term.
WARNING: Make sure you use exactly the same Collator at
index and query time -- CollationKeys are only comparable when produced by
the same Collator. Since RuleBasedCollators are not
independently versioned, it is unsafe to search against stored
CollationKeys unless the following are exactly the same (best practice is
to store this information with the index and check that they remain the
same at query time):
Collator.getInstance(java.util.Locale).
Collator.setStrength(int)
The ICUCollationKeyFilter in the icu package of Lucene's
contrib area uses ICU4J's Collator, which makes its
version available, thus allowing collation to be versioned independently
from the JVM. ICUCollationKeyFilter is also significantly faster and
generates significantly shorter keys than CollationKeyFilter. See
http://site.icu-project.org/charts/collation-icu4j-sun for key
generation timing and key length comparisons between ICU4J and
java.text.Collator over several languages.
CollationKeys generated by java.text.Collators are not compatible with those those generated by ICU Collators. Specifically, if you use CollationKeyFilter to generate index terms, do not use ICUCollationKeyFilter on the query side, or vice versa.
AttributeSource.AttributeFactory, AttributeSource.Stateinput| Constructor and Description |
|---|
CollationKeyFilter(TokenStream input,
Collator collator) |
| Modifier and Type | Method and Description |
|---|---|
boolean |
incrementToken()
Consumers (i.e.,
IndexWriter) use this method to advance the stream to
the next token. |
close, end, resetaddAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, restoreState, toStringpublic CollationKeyFilter(TokenStream input, Collator collator)
input - Source token streamcollator - CollationKey generatorpublic boolean incrementToken()
throws IOException
TokenStreamIndexWriter) use this method to advance the stream to
the next token. Implementing classes must implement this method and update
the appropriate AttributeImpls with the attributes of the next
token.
The producer must make no assumptions about the attributes after the method
has been returned: the caller may arbitrarily change it. If the producer
needs to preserve the state for subsequent calls, it can use
AttributeSource.captureState() to create a copy of the current attribute state.
This method is called for every token of a document, so an efficient
implementation is crucial for good performance. To avoid calls to
AttributeSource.addAttribute(Class) and AttributeSource.getAttribute(Class),
references to all AttributeImpls that this stream uses should be
retrieved during instantiation.
To ensure that filters and consumers know which attributes are available,
the attributes must be added during instantiation. Filters and consumers
are not required to check for availability of attributes in
TokenStream.incrementToken().
incrementToken in class TokenStreamIOException