- All Implemented Interfaces:
BytesRefIterator
The algorithm is such:
- As long as matches are successful, keep reading sequentially.
- When a match fails, skip to the next string in lexicographic order that does not enter a reject state.
The algorithm does not attempt to actually skip to the next string that is completely accepted. This is not possible when the language accepted by the FSM is not finite (i.e. * operator).
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Nested Class Summary
Nested classes/interfaces inherited from class org.apache.lucene.index.FilteredTermsEnum
FilteredTermsEnum.AcceptStatus
Nested classes/interfaces inherited from class org.apache.lucene.index.TermsEnum
TermsEnum.SeekStatus
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate final ByteRunnable
private final BytesRef
private short
private final boolean
private boolean
private final BytesRef
private final IntsRefBuilder
private final BytesRefBuilder
private final Transition
private final TransitionAccessor
private short[]
Fields inherited from class org.apache.lucene.index.FilteredTermsEnum
actualTerm, tenum
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Constructor Summary
ConstructorsConstructorDescriptionAutomatonTermsEnum
(TermsEnum tenum, CompiledAutomaton compiled) Construct an enumerator based upon an automaton, enumerating the specified field, working on a supplied TermsEnum -
Method Summary
Modifier and TypeMethodDescriptionprotected FilteredTermsEnum.AcceptStatus
Returns true if the term matches the automaton.private int
backtrack
(int position) Attempts to backtrack thru the string after encountering a dead end at some given position.private boolean
isVisited
(int state) Indicates whether the given state has been visited.protected BytesRef
nextSeekTerm
(BytesRef term) On the first call toFilteredTermsEnum.next()
or ifFilteredTermsEnum.accept(org.apache.lucene.util.BytesRef)
returnsFilteredTermsEnum.AcceptStatus.YES_AND_SEEK
orFilteredTermsEnum.AcceptStatus.NO_AND_SEEK
, this method will be called to eventually seek the underlying TermsEnum to a new position.private boolean
Increments the byte buffer to the next String in binary order after s that will not put the machine into a reject state.private boolean
nextString
(int state, int position) Returns the next String in lexicographic order that will not put the machine into a reject state.private void
setLinear
(int position) Sets the enum to operate in linear fashion, as we have found a looping transition at position: we set an upper bound and act like a TermRangeQuery for this portion of the term space.private void
setVisited
(int state) Records the given state has been visited.Methods inherited from class org.apache.lucene.index.FilteredTermsEnum
attributes, docFreq, impacts, next, ord, postings, prepareSeekExact, seekCeil, seekExact, seekExact, seekExact, setInitialSeekTerm, term, termState, totalTermFreq
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Field Details
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byteRunnable
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commonSuffixRef
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finite
private final boolean finite -
transitionAccessor
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visited
private short[] visited -
curGen
private short curGen -
seekBytesRef
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linear
private boolean linear -
linearUpperBound
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transition
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savedStates
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Constructor Details
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AutomatonTermsEnum
Construct an enumerator based upon an automaton, enumerating the specified field, working on a supplied TermsEnum- Parameters:
compiled
- CompiledAutomaton
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Method Details
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setVisited
private void setVisited(int state) Records the given state has been visited. -
isVisited
private boolean isVisited(int state) Indicates whether the given state has been visited. -
accept
Returns true if the term matches the automaton. Also stashes away the term to assist with smart enumeration.- Specified by:
accept
in classFilteredTermsEnum
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nextSeekTerm
Description copied from class:FilteredTermsEnum
On the first call toFilteredTermsEnum.next()
or ifFilteredTermsEnum.accept(org.apache.lucene.util.BytesRef)
returnsFilteredTermsEnum.AcceptStatus.YES_AND_SEEK
orFilteredTermsEnum.AcceptStatus.NO_AND_SEEK
, this method will be called to eventually seek the underlying TermsEnum to a new position. On the first call,currentTerm
will benull
, later calls will provide the term the underlying enum is positioned at. This method returns per default only one time the initial seek term and thennull
, so no repositioning is ever done.Override this method, if you want a more sophisticated TermsEnum, that repositions the iterator during enumeration. If this method always returns
null
the enum is empty.Please note: This method should always provide a greater term than the last enumerated term, else the behaviour of this enum violates the contract for TermsEnums.
- Overrides:
nextSeekTerm
in classFilteredTermsEnum
- Throws:
IOException
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setLinear
private void setLinear(int position) Sets the enum to operate in linear fashion, as we have found a looping transition at position: we set an upper bound and act like a TermRangeQuery for this portion of the term space. -
nextString
private boolean nextString()Increments the byte buffer to the next String in binary order after s that will not put the machine into a reject state. If such a string does not exist, returns false.The correctness of this method depends upon the automaton being deterministic, and having no transitions to dead states.
- Returns:
- true if more possible solutions exist for the DFA
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nextString
private boolean nextString(int state, int position) Returns the next String in lexicographic order that will not put the machine into a reject state.This method traverses the DFA from the given position in the String, starting at the given state.
If this cannot satisfy the machine, returns false. This method will walk the minimal path, in lexicographic order, as long as possible.
If this method returns false, then there might still be more solutions, it is necessary to backtrack to find out.
- Parameters:
state
- current non-reject stateposition
- useful portion of the string- Returns:
- true if more possible solutions exist for the DFA from this position
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backtrack
private int backtrack(int position) Attempts to backtrack thru the string after encountering a dead end at some given position. Returns false if no more possible strings can match.- Parameters:
position
- current position in the input String- Returns:
position >= 0
if more possible solutions exist for the DFA
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