# Uses of Package
org.apache.lucene.index

- Packages that use org.apache.lucene.index
  Package | Description
  --- | ---
  org.apache.lucene.codecs | Codecs API: API for customization of the encoding and structure of the index.
  org.apache.lucene.codecs.blocktree | BlockTree terms dictionary.
  org.apache.lucene.codecs.compressing | StoredFieldsFormat that allows cross-document and cross-field compression of stored fields.
  org.apache.lucene.codecs.lucene50 | Components from the Lucene 5.0 index format See `org.apache.lucene.codecs.lucene80` for an overview of the index format.
  org.apache.lucene.codecs.lucene60 | Components from the Lucene 6.0 index format.
  org.apache.lucene.codecs.lucene80 | Components from the Lucene 8.0 index format See `org.apache.lucene.codecs.lucene84` for an overview of the index format.
  org.apache.lucene.codecs.lucene84 | Components from the Lucene 8.4 index format.
  org.apache.lucene.codecs.lucene86 | Lucene 8.6 file format.
  org.apache.lucene.codecs.lucene87 | Lucene 8.7 file format.
  org.apache.lucene.codecs.perfield | Postings format that can delegate to different formats per-field.
  org.apache.lucene.document | The logical representation of a `Document` for indexing and searching.
  org.apache.lucene.geo | Geospatial Utility Implementations for Lucene Core
  org.apache.lucene.index | Code to maintain and access indices.
  org.apache.lucene.search | Code to search indices.
  org.apache.lucene.search.comparators | Comparators, used to compare hits so as to determine their sort order when collecting the top results with `TopFieldCollector`.
  org.apache.lucene.search.similarities | This package contains the various ranking models that can be used in Lucene.
  org.apache.lucene.search.spans | The calculus of spans.
  org.apache.lucene.util | Some utility classes.
  org.apache.lucene.util.automaton | Finite-state automaton for regular expressions.
  org.apache.lucene.util.bkd | Block KD-tree, implementing the generic spatial data structure described in this paper.
  org.apache.lucene.util.graph | Utility classes for working with token streams as graphs.

- Classes in org.apache.lucene.index used by org.apache.lucene.codecs
  Class and Description
  BinaryDocValues A per-document numeric value.
  FieldInfo Access to the Field Info file that describes document fields and whether or not they are indexed.
  FieldInfos Collection of `FieldInfo`s (accessible by number or by name).
  Fields Provides a `Terms` index for fields that have it, and lists which fields do.
  Impact Per-document scoring factors.
  ImpactsEnum Extension of `PostingsEnum` which also provides information about upcoming impacts.
  IndexableField Represents a single field for indexing.
  IndexableFieldType Describes the properties of a field.
  IndexOptions Controls how much information is stored in the postings lists.
  MergeState Holds common state used during segment merging.
  NumericDocValues A per-document numeric value.
  OrdTermState An ordinal based `TermState`
  PointValues Access to indexed numeric values.
  PostingsEnum Iterates through the postings.
  SegmentCommitInfo Embeds a [read-only] SegmentInfo and adds per-commit fields.
  SegmentInfo Information about a segment such as its name, directory, and files related to the segment.
  SegmentReadState Holder class for common parameters used during read.
  SegmentWriteState Holder class for common parameters used during write.
  SortedDocValues A per-document byte[] with presorted values.
  SortedNumericDocValues A list of per-document numeric values, sorted according to `Long.compare(long, long)`.
  SortedSetDocValues A multi-valued version of `SortedDocValues`.
  StoredFieldVisitor Expert: provides a low-level means of accessing the stored field values in an index.
  StoredFieldVisitor.Status Enumeration of possible return values for `StoredFieldVisitor.needsField(org.apache.lucene.index.FieldInfo)`.
  TermsEnum Iterator to seek (`TermsEnum.seekCeil(BytesRef)`, `TermsEnum.seekExact(BytesRef)`) or step through (`BytesRefIterator.next()` terms to obtain frequency information (`TermsEnum.docFreq()`), `PostingsEnum` or `PostingsEnum` for the current term (`TermsEnum.postings(org.apache.lucene.index.PostingsEnum)`.
  TermState Encapsulates all required internal state to position the associated `TermsEnum` without re-seeking.

- Classes in org.apache.lucene.index used by org.apache.lucene.codecs.blocktree
  Class and Description
  Fields Provides a `Terms` index for fields that have it, and lists which fields do.
  SegmentReadState Holder class for common parameters used during read.
  SegmentWriteState Holder class for common parameters used during write.
  Terms Access to the terms in a specific field.
  TermsEnum Iterator to seek (`TermsEnum.seekCeil(BytesRef)`, `TermsEnum.seekExact(BytesRef)`) or step through (`BytesRefIterator.next()` terms to obtain frequency information (`TermsEnum.docFreq()`), `PostingsEnum` or `PostingsEnum` for the current term (`TermsEnum.postings(org.apache.lucene.index.PostingsEnum)`.

- Classes in org.apache.lucene.index used by org.apache.lucene.codecs.compressing
  Class and Description
  FieldInfo Access to the Field Info file that describes document fields and whether or not they are indexed.
  FieldInfos Collection of `FieldInfo`s (accessible by number or by name).
  Fields Provides a `Terms` index for fields that have it, and lists which fields do.
  IndexableField Represents a single field for indexing.
  MergeState Holds common state used during segment merging.
  SegmentInfo Information about a segment such as its name, directory, and files related to the segment.
  StoredFieldVisitor Expert: provides a low-level means of accessing the stored field values in an index.

- Classes in org.apache.lucene.index used by org.apache.lucene.codecs.lucene50
  Class and Description
  FieldInfos Collection of `FieldInfo`s (accessible by number or by name).
  SegmentCommitInfo Embeds a [read-only] SegmentInfo and adds per-commit fields.
  SegmentInfo Information about a segment such as its name, directory, and files related to the segment.

- Classes in org.apache.lucene.index used by org.apache.lucene.codecs.lucene60
  Class and Description
  FieldInfos Collection of `FieldInfo`s (accessible by number or by name).
  SegmentInfo Information about a segment such as its name, directory, and files related to the segment.

- Classes in org.apache.lucene.index used by org.apache.lucene.codecs.lucene80
  Class and Description
  SegmentReadState Holder class for common parameters used during read.
  SegmentWriteState Holder class for common parameters used during write.

- Classes in org.apache.lucene.index used by org.apache.lucene.codecs.lucene84
  Class and Description
  FieldInfo Access to the Field Info file that describes document fields and whether or not they are indexed.
  ImpactsEnum Extension of `PostingsEnum` which also provides information about upcoming impacts.
  NumericDocValues A per-document numeric value.
  OrdTermState An ordinal based `TermState`
  PostingsEnum Iterates through the postings.
  SegmentReadState Holder class for common parameters used during read.
  SegmentWriteState Holder class for common parameters used during write.
  TermState Encapsulates all required internal state to position the associated `TermsEnum` without re-seeking.

- Classes in org.apache.lucene.index used by org.apache.lucene.codecs.lucene86
  Class and Description
  FieldInfo Access to the Field Info file that describes document fields and whether or not they are indexed.
  MergeState Holds common state used during segment merging.
  PointValues Access to indexed numeric values.
  SegmentInfo Information about a segment such as its name, directory, and files related to the segment.
  SegmentReadState Holder class for common parameters used during read.
  SegmentWriteState Holder class for common parameters used during write.

- Classes in org.apache.lucene.index used by org.apache.lucene.codecs.lucene87
  Class and Description
  FieldInfos Collection of `FieldInfo`s (accessible by number or by name).
  SegmentInfo Information about a segment such as its name, directory, and files related to the segment.

- Classes in org.apache.lucene.index used by org.apache.lucene.codecs.perfield
  Class and Description
  SegmentReadState Holder class for common parameters used during read.
  SegmentWriteState Holder class for common parameters used during write.

- Classes in org.apache.lucene.index used by org.apache.lucene.document
  Class and Description
  DocValuesType DocValues types.
  FieldInfo Access to the Field Info file that describes document fields and whether or not they are indexed.
  IndexableField Represents a single field for indexing.
  IndexableFieldType Describes the properties of a field.
  IndexOptions Controls how much information is stored in the postings lists.
  StoredFieldVisitor Expert: provides a low-level means of accessing the stored field values in an index.
  StoredFieldVisitor.Status Enumeration of possible return values for `StoredFieldVisitor.needsField(org.apache.lucene.index.FieldInfo)`.

- Classes in org.apache.lucene.index used by org.apache.lucene.geo
  Class and Description
  PointValues.Relation Used by `PointValues.intersect(org.apache.lucene.index.PointValues.IntersectVisitor)` to check how each recursive cell corresponds to the query.

- Classes in org.apache.lucene.index used by org.apache.lucene.index
  Class and Description
  BaseCompositeReader Base class for implementing `CompositeReader`s based on an array of sub-readers.
  BaseTermsEnum A base TermsEnum that adds default implementations for `BaseTermsEnum.attributes()` `BaseTermsEnum.termState()` `BaseTermsEnum.seekExact(BytesRef)` `BaseTermsEnum.seekExact(BytesRef, TermState)` In some cases, the default implementation may be slow and consume huge memory, so subclass SHOULD have its own implementation if possible.
  BinaryDocValues A per-document numeric value.
  CheckIndex.Options Run-time configuration options for CheckIndex commands.
  CheckIndex.Status Returned from `CheckIndex.checkIndex()` detailing the health and status of the index.
  CheckIndex.Status.DocValuesStatus Status from testing DocValues
  CheckIndex.Status.FieldInfoStatus Status from testing field infos.
  CheckIndex.Status.FieldNormStatus Status from testing field norms.
  CheckIndex.Status.IndexSortStatus Status from testing index sort
  CheckIndex.Status.LiveDocStatus Status from testing livedocs
  CheckIndex.Status.PointsStatus Status from testing PointValues
  CheckIndex.Status.SegmentInfoStatus Holds the status of each segment in the index.
  CheckIndex.Status.StoredFieldStatus Status from testing stored fields.
  CheckIndex.Status.TermIndexStatus Status from testing term index.
  CheckIndex.Status.TermVectorStatus Status from testing stored fields.
  CodecReader LeafReader implemented by codec APIs.
  CompositeReader Instances of this reader type can only be used to get stored fields from the underlying LeafReaders, but it is not possible to directly retrieve postings.
  CompositeReaderContext `IndexReaderContext` for `CompositeReader` instance.
  ConcurrentMergeScheduler.MergeThread Runs a merge thread to execute a single merge, then exits.
  DirectoryReader DirectoryReader is an implementation of `CompositeReader` that can read indexes in a `Directory`.
  DocIDMerger Utility class to help merging documents from sub-readers according to either simple concatenated (unsorted) order, or by a specified index-time sort, skipping deleted documents and remapping non-deleted documents.
  DocIDMerger.Sub Represents one sub-reader being merged
  DocValuesType DocValues types.
  FieldInfo Access to the Field Info file that describes document fields and whether or not they are indexed.
  FieldInfos Collection of `FieldInfo`s (accessible by number or by name).
  Fields Provides a `Terms` index for fields that have it, and lists which fields do.
  FilterCodecReader A `FilterCodecReader` contains another CodecReader, which it uses as its basic source of data, possibly transforming the data along the way or providing additional functionality.
  FilterDirectoryReader A FilterDirectoryReader wraps another DirectoryReader, allowing implementations to transform or extend it.
  FilterDirectoryReader.SubReaderWrapper Factory class passed to FilterDirectoryReader constructor that allows subclasses to wrap the filtered DirectoryReader's subreaders.
  FilteredTermsEnum Abstract class for enumerating a subset of all terms.
  FilteredTermsEnum.AcceptStatus Return value, if term should be accepted or the iteration should `END`.
  FilterLeafReader A `FilterLeafReader` contains another LeafReader, which it uses as its basic source of data, possibly transforming the data along the way or providing additional functionality.
  FilterLeafReader.FilterFields Base class for filtering `Fields` implementations.
  FilterLeafReader.FilterTerms Base class for filtering `Terms` implementations.
  FilterLeafReader.FilterTermsEnum Base class for filtering `TermsEnum` implementations.
  FilterMergePolicy A wrapper for `MergePolicy` instances.
  Impact Per-document scoring factors.
  Impacts Information about upcoming impacts, ie.
  ImpactsEnum Extension of `PostingsEnum` which also provides information about upcoming impacts.
  ImpactsSource Source of `Impacts`.
  IndexableField Represents a single field for indexing.
  IndexableFieldType Describes the properties of a field.
  IndexCommit Expert: represents a single commit into an index as seen by the `IndexDeletionPolicy` or `IndexReader`.
  IndexDeletionPolicy Expert: policy for deletion of stale `index commits`.
  IndexOptions Controls how much information is stored in the postings lists.
  IndexReader IndexReader is an abstract class, providing an interface for accessing a point-in-time view of an index.
  IndexReader.CacheHelper A utility class that gives hooks in order to help build a cache based on the data that is contained in this index.
  IndexReader.CacheKey A cache key identifying a resource that is being cached on.
  IndexReader.ClosedListener A listener that is called when a resource gets closed.
  IndexReaderContext A struct like class that represents a hierarchical relationship between `IndexReader` instances.
  IndexSorter Handles how documents should be sorted in an index, both within a segment and between segments.
  IndexSorter.ComparableProvider Used for sorting documents across segments
  IndexSorter.DocComparator A comparator of doc IDs, used for sorting documents within a segment
  IndexSorter.NumericDocValuesProvider Provide a NumericDocValues instance for a LeafReader
  IndexSorter.SortedDocValuesProvider Provide a SortedDocValues instance for a LeafReader
  IndexWriter An `IndexWriter` creates and maintains an index.
  IndexWriter.DocStats DocStats for this index
  IndexWriter.IndexReaderWarmer If `DirectoryReader.open(IndexWriter)` has been called (ie, this writer is in near real-time mode), then after a merge completes, this class can be invoked to warm the reader on the newly merged segment, before the merge commits.
  IndexWriterConfig Holds all the configuration that is used to create an `IndexWriter`.
  IndexWriterConfig.OpenMode Specifies the open mode for `IndexWriter`.
  LeafMetaData Provides read-only metadata about a leaf.
  LeafReader `LeafReader` is an abstract class, providing an interface for accessing an index.
  LeafReaderContext `IndexReaderContext` for `LeafReader` instances.
  LiveIndexWriterConfig Holds all the configuration used by `IndexWriter` with few setters for settings that can be changed on an `IndexWriter` instance "live".
  LogMergePolicy This class implements a `MergePolicy` that tries to merge segments into levels of exponentially increasing size, where each level has fewer segments than the value of the merge factor.
  MergePolicy Expert: a MergePolicy determines the sequence of primitive merge operations.
  MergePolicy.MergeAbortedException Thrown when a merge was explicitly aborted because `IndexWriter.abortMerges()` was called.
  MergePolicy.MergeContext This interface represents the current context of the merge selection process.
  MergePolicy.MergeSpecification A MergeSpecification instance provides the information necessary to perform multiple merges.
  MergePolicy.OneMerge OneMerge provides the information necessary to perform an individual primitive merge operation, resulting in a single new segment.
  MergePolicy.OneMergeProgress Progress and state for an executing merge.
  MergePolicy.OneMergeProgress.PauseReason Reason for pausing the merge thread.
  MergeScheduler Expert: `IndexWriter` uses an instance implementing this interface to execute the merges selected by a `MergePolicy`.
  MergeScheduler.MergeSource Provides access to new merges and executes the actual merge
  MergeState Holds common state used during segment merging.
  MergeState.DocMap A map of doc IDs.
  MergeTrigger MergeTrigger is passed to `MergePolicy.findMerges(MergeTrigger, SegmentInfos, MergePolicy.MergeContext)` to indicate the event that triggered the merge.
  MultiFields Provides a single `Fields` term index view over an `IndexReader`.
  MultiPostingsEnum Exposes `PostingsEnum`, merged from `PostingsEnum` API of sub-segments.
  MultiPostingsEnum.EnumWithSlice Holds a `PostingsEnum` along with the corresponding `ReaderSlice`.
  MultiTermsEnum Exposes `TermsEnum` API, merged from `TermsEnum` API of sub-segments.
  NumericDocValues A per-document numeric value.
  OneMergeWrappingMergePolicy A wrapping merge policy that wraps the `MergePolicy.OneMerge` objects returned by the wrapped merge policy.
  OrdinalMap Maps per-segment ordinals to/from global ordinal space, using a compact packed-ints representation.
  PointValues Access to indexed numeric values.
  PointValues.IntersectVisitor We recurse the BKD tree, using a provided instance of this to guide the recursion.
  PointValues.Relation Used by `PointValues.intersect(org.apache.lucene.index.PointValues.IntersectVisitor)` to check how each recursive cell corresponds to the query.
  PostingsEnum Iterates through the postings.
  PrefixCodedTerms Prefix codes term instances (prefixes are shared).
  PrefixCodedTerms.TermIterator An iterator over the list of terms stored in a `PrefixCodedTerms`.
  QueryTimeout Base for query timeout implementations, which will provide a `shouldExit()` method, used with `ExitableDirectoryReader`.
  ReaderSlice Subreader slice from a parent composite reader.
  SegmentCommitInfo Embeds a [read-only] SegmentInfo and adds per-commit fields.
  SegmentInfo Information about a segment such as its name, directory, and files related to the segment.
  SegmentInfos A collection of segmentInfo objects with methods for operating on those segments in relation to the file system.
  SegmentReadState Holder class for common parameters used during read.
  SegmentWriteState Holder class for common parameters used during write.
  SnapshotDeletionPolicy An `IndexDeletionPolicy` that wraps any other `IndexDeletionPolicy` and adds the ability to hold and later release snapshots of an index.
  SortedDocValues A per-document byte[] with presorted values.
  SortedNumericDocValues A list of per-document numeric values, sorted according to `Long.compare(long, long)`.
  SortedSetDocValues A multi-valued version of `SortedDocValues`.
  SortFieldProvider Reads/Writes a named SortField from a segment info file, used to record index sorts
  StoredFieldVisitor Expert: provides a low-level means of accessing the stored field values in an index.
  StoredFieldVisitor.Status Enumeration of possible return values for `StoredFieldVisitor.needsField(org.apache.lucene.index.FieldInfo)`.
  Term A Term represents a word from text.
  Terms Access to the terms in a specific field.
  TermsEnum Iterator to seek (`TermsEnum.seekCeil(BytesRef)`, `TermsEnum.seekExact(BytesRef)`) or step through (`BytesRefIterator.next()` terms to obtain frequency information (`TermsEnum.docFreq()`), `PostingsEnum` or `PostingsEnum` for the current term (`TermsEnum.postings(org.apache.lucene.index.PostingsEnum)`.
  TermsEnum.SeekStatus Represents returned result from `TermsEnum.seekCeil(org.apache.lucene.util.BytesRef)`.
  TermState Encapsulates all required internal state to position the associated `TermsEnum` without re-seeking.
  TermStates Maintains a `IndexReader` `TermState` view over `IndexReader` instances containing a single term.
  TieredMergePolicy Merges segments of approximately equal size, subject to an allowed number of segments per tier.
  TieredMergePolicy.MergeScore Holds score and explanation for a single candidate merge.
  TwoPhaseCommit An interface for implementations that support 2-phase commit.
  TwoPhaseCommitTool.CommitFailException Thrown by `TwoPhaseCommitTool.execute(TwoPhaseCommit...)` when an object fails to commit().
  TwoPhaseCommitTool.PrepareCommitFailException Thrown by `TwoPhaseCommitTool.execute(TwoPhaseCommit...)` when an object fails to prepareCommit().

- Classes in org.apache.lucene.index used by org.apache.lucene.search
  Class and Description
  BinaryDocValues A per-document numeric value.
  DirectoryReader DirectoryReader is an implementation of `CompositeReader` that can read indexes in a `Directory`.
  ImpactsEnum Extension of `PostingsEnum` which also provides information about upcoming impacts.
  ImpactsSource Source of `Impacts`.
  IndexReader IndexReader is an abstract class, providing an interface for accessing a point-in-time view of an index.
  IndexReaderContext A struct like class that represents a hierarchical relationship between `IndexReader` instances.
  IndexSorter Handles how documents should be sorted in an index, both within a segment and between segments.
  IndexWriter An `IndexWriter` creates and maintains an index.
  LeafReader `LeafReader` is an abstract class, providing an interface for accessing an index.
  LeafReaderContext `IndexReaderContext` for `LeafReader` instances.
  NumericDocValues A per-document numeric value.
  PostingsEnum Iterates through the postings.
  PrefixCodedTerms Prefix codes term instances (prefixes are shared).
  SortedDocValues A per-document byte[] with presorted values.
  SortedNumericDocValues A list of per-document numeric values, sorted according to `Long.compare(long, long)`.
  SortedSetDocValues A multi-valued version of `SortedDocValues`.
  SortFieldProvider Reads/Writes a named SortField from a segment info file, used to record index sorts
  StoredFieldVisitor Expert: provides a low-level means of accessing the stored field values in an index.
  Term A Term represents a word from text.
  Terms Access to the terms in a specific field.
  TermsEnum Iterator to seek (`TermsEnum.seekCeil(BytesRef)`, `TermsEnum.seekExact(BytesRef)`) or step through (`BytesRefIterator.next()` terms to obtain frequency information (`TermsEnum.docFreq()`), `PostingsEnum` or `PostingsEnum` for the current term (`TermsEnum.postings(org.apache.lucene.index.PostingsEnum)`.
  TermsEnum.SeekStatus Represents returned result from `TermsEnum.seekCeil(org.apache.lucene.util.BytesRef)`.
  TermState Encapsulates all required internal state to position the associated `TermsEnum` without re-seeking.
  TermStates Maintains a `IndexReader` `TermState` view over `IndexReader` instances containing a single term.

- Classes in org.apache.lucene.index used by org.apache.lucene.search.comparators
  Class and Description
  LeafReaderContext `IndexReaderContext` for `LeafReader` instances.
  NumericDocValues A per-document numeric value.

- Classes in org.apache.lucene.index used by org.apache.lucene.search.similarities
  Class and Description
  FieldInvertState This class tracks the number and position / offset parameters of terms being added to the index.

- Classes in org.apache.lucene.index used by org.apache.lucene.search.spans
  Class and Description
  IndexReader IndexReader is an abstract class, providing an interface for accessing a point-in-time view of an index.
  LeafReaderContext `IndexReaderContext` for `LeafReader` instances.
  PostingsEnum Iterates through the postings.
  Term A Term represents a word from text.
  TermStates Maintains a `IndexReader` `TermState` view over `IndexReader` instances containing a single term.

- Classes in org.apache.lucene.index used by org.apache.lucene.util
  Class and Description
  PointValues Access to indexed numeric values.
  Term A Term represents a word from text.
  Terms Access to the terms in a specific field.

- Classes in org.apache.lucene.index used by org.apache.lucene.util.automaton
  Class and Description
  Terms Access to the terms in a specific field.
  TermsEnum Iterator to seek (`TermsEnum.seekCeil(BytesRef)`, `TermsEnum.seekExact(BytesRef)`) or step through (`BytesRefIterator.next()` terms to obtain frequency information (`TermsEnum.docFreq()`), `PostingsEnum` or `PostingsEnum` for the current term (`TermsEnum.postings(org.apache.lucene.index.PostingsEnum)`.

- Classes in org.apache.lucene.index used by org.apache.lucene.util.bkd
  Class and Description
  MergeState.DocMap A map of doc IDs.
  PointValues Access to indexed numeric values.
  PointValues.IntersectVisitor We recurse the BKD tree, using a provided instance of this to guide the recursion.

- Classes in org.apache.lucene.index used by org.apache.lucene.util.graph
  Class and Description
  Term A Term represents a word from text.

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