Class SynonymFilter
- All Implemented Interfaces:
Closeable
,AutoCloseable
,Unwrappable<TokenStream>
Note that with the current implementation, parsing is greedy, so whenever multiple parses would apply, the rule starting the earliest and parsing the most tokens wins. For example if you have these rules:
a -> x a b -> y b c d -> zThen input
a b c d e
parses to y b c
d
, ie the 2nd rule "wins" because it started earliest and matched the most input tokens of
other rules starting at that point.
A future improvement to this filter could allow non-greedy parsing, such that the 3rd rule would win, and also separately allow multiple parses, such that all 3 rules would match, perhaps even on a rule by rule basis.
NOTE: when a match occurs, the output tokens associated with the matching rule are
"stacked" on top of the input stream (if the rule had keepOrig=true
) and also on top
of another matched rule's output tokens. This is not a correct solution, as really the output
should be an arbitrary graph/lattice. For example, with the above match, you would expect an
exact PhraseQuery
"y b
c"
to match the parsed tokens, but it will fail to do so. This limitation is necessary
because Lucene's TokenStream (and index) cannot yet represent an arbitrary graph.
NOTE: If multiple incoming tokens arrive on the same position, only the first token at that position is used for parsing. Subsequent tokens simply pass through and are not parsed. A future improvement would be to allow these tokens to also be matched.
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Nested Class Summary
Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.State
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Field Summary
Fields inherited from class org.apache.lucene.analysis.TokenFilter
input
Fields inherited from class org.apache.lucene.analysis.TokenStream
DEFAULT_TOKEN_ATTRIBUTE_FACTORY
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Constructor Summary
ConstructorDescriptionSynonymFilter
(TokenStream input, SynonymMap synonyms, boolean ignoreCase) Deprecated. -
Method Summary
Methods inherited from class org.apache.lucene.analysis.TokenFilter
close, end, unwrap
Methods inherited from class org.apache.lucene.util.AttributeSource
addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, endAttributes, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, removeAllAttributes, restoreState, toString
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Field Details
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TYPE_SYNONYM
Deprecated.- See Also:
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Constructor Details
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SynonymFilter
Deprecated.- Parameters:
input
- input tokenstreamsynonyms
- synonym mapignoreCase
- case-folds input for matching withCharacter.toLowerCase(int)
. Note, if you set this to true, it's your responsibility to lowercase the input entries when you create theSynonymMap
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Method Details
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incrementToken
Deprecated.- Specified by:
incrementToken
in classTokenStream
- Throws:
IOException
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reset
Deprecated.- Overrides:
reset
in classTokenFilter
- Throws:
IOException
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SynonymGraphFilter
instead, but be sure to also useFlattenGraphFilter
at index time (not at search time) as well.