org.apache.lucene.search

## Class AutomatonQuery

- java.lang.Object
- - org.apache.lucene.search.Query
  - - org.apache.lucene.search.MultiTermQuery
    - - org.apache.lucene.search.AutomatonQuery

- Direct Known Subclasses:
    PrefixQuery, RegexpQuery, TermRangeQuery, WildcardQuery

      public class AutomatonQuery
      extends MultiTermQuery

  A `Query` that will match terms against a finite-state machine.

  This query will match documents that contain terms accepted by a given finite-state machine. The automaton can be constructed with the `org.apache.lucene.util.automaton` API. Alternatively, it can be created from a regular expression with `RegexpQuery` or from the standard Lucene wildcard syntax with `WildcardQuery`.

  When the query is executed, it will create an equivalent DFA of the finite-state machine, and will enumerate the term dictionary in an intelligent way to reduce the number of comparisons. For example: the regular expression of `[dl]og?` will make approximately four comparisons: do, dog, lo, and log.

  WARNING: This API is experimental and might change in incompatible ways in the next release.

- - ### Nested Class Summary

    - ### Nested classes/interfaces inherited from class org.apache.lucene.search.MultiTermQuery

      `MultiTermQuery.RewriteMethod, MultiTermQuery.TopTermsBlendedFreqScoringRewrite, MultiTermQuery.TopTermsBoostOnlyBooleanQueryRewrite, MultiTermQuery.TopTermsScoringBooleanQueryRewrite`

  - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected Automaton` | `automaton` the automaton to match index terms against
    `protected boolean` | `automatonIsBinary`
    `protected CompiledAutomaton` | `compiled`
    `protected Term` | `term` term containing the field, and possibly some pattern structure

    - ### Fields inherited from class org.apache.lucene.search.MultiTermQuery

      `CONSTANT_SCORE_BOOLEAN_REWRITE, CONSTANT_SCORE_REWRITE, field, rewriteMethod, SCORING_BOOLEAN_REWRITE`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `AutomatonQuery(Term term, Automaton automaton)` Create a new AutomatonQuery from an `Automaton`.
    `AutomatonQuery(Term term, Automaton automaton, int maxDeterminizedStates)` Create a new AutomatonQuery from an `Automaton`.
    `AutomatonQuery(Term term, Automaton automaton, int maxDeterminizedStates, boolean isBinary)` Create a new AutomatonQuery from an `Automaton`.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `boolean` | `equals(Object obj)` Override and implement query instance equivalence properly in a subclass.
    `Automaton` | `getAutomaton()` Returns the automaton used to create this query
    `protected TermsEnum` | `getTermsEnum(Terms terms, AttributeSource atts)` Construct the enumeration to be used, expanding the pattern term.
    `int` | `hashCode()` Override and implement query hash code properly in a subclass.
    `boolean` | `isAutomatonBinary()` Is this a binary (byte) oriented automaton.
    `String` | `toString(String field)` Prints a query to a string, with `field` assumed to be the default field and omitted.

    - ### Methods inherited from class org.apache.lucene.search.MultiTermQuery

      `getField, getRewriteMethod, getTermsEnum, rewrite, setRewriteMethod`

    - ### Methods inherited from class org.apache.lucene.search.Query

      `classHash, createWeight, sameClassAs, toString`

    - ### Methods inherited from class java.lang.Object

      `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

- - ### Field Detail

    - #### automaton

          protected final Automaton automaton

      the automaton to match index terms against

    - #### compiled

          protected final CompiledAutomaton compiled

    - #### term

          protected final Term term

      term containing the field, and possibly some pattern structure

    - #### automatonIsBinary

          protected final boolean automatonIsBinary

  - ### Constructor Detail

    - #### AutomatonQuery

          public AutomatonQuery(Term term,
                                Automaton automaton)

      Create a new AutomatonQuery from an `Automaton`.
      Parameters:
        `term` - Term containing field and possibly some pattern structure. The term text is ignored.
        `automaton` - Automaton to run, terms that are accepted are considered a match.

    - #### AutomatonQuery

          public AutomatonQuery(Term term,
                                Automaton automaton,
                                int maxDeterminizedStates)

      Create a new AutomatonQuery from an `Automaton`.
      Parameters:
        `term` - Term containing field and possibly some pattern structure. The term text is ignored.
        `automaton` - Automaton to run, terms that are accepted are considered a match.
        `maxDeterminizedStates` - maximum number of states in the resulting automata. If the automata would need more than this many states TooComplextToDeterminizeException is thrown. Higher number require more space but can process more complex automata.

    - #### AutomatonQuery

          public AutomatonQuery(Term term,
                                Automaton automaton,
                                int maxDeterminizedStates,
                                boolean isBinary)

      Create a new AutomatonQuery from an `Automaton`.
      Parameters:
        `term` - Term containing field and possibly some pattern structure. The term text is ignored.
        `automaton` - Automaton to run, terms that are accepted are considered a match.
        `maxDeterminizedStates` - maximum number of states in the resulting automata. If the automata would need more than this many states TooComplextToDeterminizeException is thrown. Higher number require more space but can process more complex automata.
        `isBinary` - if true, this automaton is already binary and will not go through the UTF32ToUTF8 conversion

  - ### Method Detail

    - #### getTermsEnum

          protected TermsEnum getTermsEnum(Terms terms,
                                           AttributeSource atts)
                                    throws IOException

      Description copied from class: `MultiTermQuery`
      Construct the enumeration to be used, expanding the pattern term. This method should only be called if the field exists (ie, implementations can assume the field does exist). This method should not return null (should instead return `TermsEnum.EMPTY` if no terms match). The TermsEnum must already be positioned to the first matching term. The given `AttributeSource` is passed by the `MultiTermQuery.RewriteMethod` to provide attributes, the rewrite method uses to inform about e.g. maximum competitive boosts. This is currently only used by `TopTermsRewrite`
      Specified by:
        `getTermsEnum` in class `MultiTermQuery`
      Throws:
        `IOException`

    - #### hashCode

          public int hashCode()

      Description copied from class: `Query`
      Override and implement query hash code properly in a subclass. This is required so that `QueryCache` works properly.
      Overrides:
        `hashCode` in class `MultiTermQuery`
      See Also:
        `Query.equals(Object)`

    - #### equals

          public boolean equals(Object obj)

      Description copied from class: `Query`
      Override and implement query instance equivalence properly in a subclass. This is required so that `QueryCache` works properly. Typically a query will be equal to another only if it's an instance of the same class and its document-filtering properties are identical that other instance. Utility methods are provided for certain repetitive code.
      Overrides:
        `equals` in class `MultiTermQuery`
      See Also:
        `Query.sameClassAs(Object)`, `Query.classHash()`

    - #### toString

          public String toString(String field)

      Description copied from class: `Query`
      Prints a query to a string, with `field` assumed to be the default field and omitted.
      Specified by:
        `toString` in class `Query`

    - #### getAutomaton

          public Automaton getAutomaton()

      Returns the automaton used to create this query

    - #### isAutomatonBinary

          public boolean isAutomatonBinary()

      Is this a binary (byte) oriented automaton. See the constructor.

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