Package org.apache.lucene.index

Class MultiFields

java.lang.Object

org.apache.lucene.index.Fields

org.apache.lucene.index.MultiFields

All Implemented Interfaces:

Iterable<String>

public final class MultiFields
extends Fields

Provides a single Fields term index view over an IndexReader. This is useful when you're interacting with an IndexReader implementation that consists of sequential sub-readers (eg DirectoryReader or MultiReader) and you must treat it as a LeafReader.

NOTE: for composite readers, you'll get better performance by gathering the sub readers using IndexReader.getContext() to get the atomic leaves and then operate per-LeafReader, instead of using this class.

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

Field Summary

Fields inherited from class org.apache.lucene.index.Fields

EMPTY_ARRAY

Constructor Summary

Constructors

Constructor	Description
MultiFields(Fields[] subs, ReaderSlice[] subSlices)	Expert: construct a new MultiFields instance directly.

Method Summary

Modifier and Type	Method	Description
static Fields	getFields(IndexReader reader)	Returns a single Fields instance for this reader, merging fields/terms/docs/positions on the fly.
static Collection<String>	getIndexedFields(IndexReader reader)	Call this to get the (merged) FieldInfos representing the set of indexed fields only for a composite reader.
static Bits	getLiveDocs(IndexReader reader)	Returns a single Bits instance for this reader, merging live Documents on the fly.
static FieldInfos	getMergedFieldInfos(IndexReader reader)	Call this to get the (merged) FieldInfos for a composite reader.
static PostingsEnum	getTermDocsEnum(IndexReader r, String field, BytesRef term)	Returns PostingsEnum for the specified field and term.
static PostingsEnum	getTermDocsEnum(IndexReader r, String field, BytesRef term, int flags)	Returns PostingsEnum for the specified field and term, with control over whether freqs are required.
static PostingsEnum	getTermPositionsEnum(IndexReader r, String field, BytesRef term)	Returns PostingsEnum for the specified field and term.
static PostingsEnum	getTermPositionsEnum(IndexReader r, String field, BytesRef term, int flags)	Returns PostingsEnum for the specified field and term, with control over whether offsets and payloads are required.
static Terms	getTerms(IndexReader r, String field)	This method may return null if the field does not exist or if it has no terms.
Iterator<String>	iterator()	Returns an iterator that will step through all fields names.
int	size()	Returns the number of fields or -1 if the number of distinct field names is unknown.
Terms	terms(String field)	Get the Terms for this field.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Constructor Detail

MultiFields

public MultiFields(Fields[] subs,
                   ReaderSlice[] subSlices)

Expert: construct a new MultiFields instance directly.

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

Method Detail

getFields

public static Fields getFields(IndexReader reader)
                        throws IOException

Returns a single Fields instance for this reader, merging fields/terms/docs/positions on the fly. This method will return null if the reader has no postings.

NOTE: this is a slow way to access postings. It's better to get the sub-readers and iterate through them yourself.

Throws:

IOException

getLiveDocs

public static Bits getLiveDocs(IndexReader reader)

Returns a single Bits instance for this reader, merging live Documents on the fly. This method will return null if the reader has no deletions.

NOTE: this is a very slow way to access live docs. For example, each Bits access will require a binary search. It's better to get the sub-readers and iterate through them yourself.

getTerms

public static Terms getTerms(IndexReader r,
                             String field)
                      throws IOException

This method may return null if the field does not exist or if it has no terms.

Throws:

IOException

getTermDocsEnum

public static PostingsEnum getTermDocsEnum(IndexReader r,
                                           String field,
                                           BytesRef term)
                                    throws IOException

Returns PostingsEnum for the specified field and term. This will return null if the field or term does not exist.

Throws:

IOException

getTermDocsEnum

public static PostingsEnum getTermDocsEnum(IndexReader r,
                                           String field,
                                           BytesRef term,
                                           int flags)
                                    throws IOException

Returns PostingsEnum for the specified field and term, with control over whether freqs are required. Some codecs may be able to optimize their implementation when freqs are not required. This will return null if the field or term does not exist. See TermsEnum.postings(PostingsEnum,int).

Throws:

IOException

getTermPositionsEnum

public static PostingsEnum getTermPositionsEnum(IndexReader r,
                                                String field,
                                                BytesRef term)
                                         throws IOException

Returns PostingsEnum for the specified field and term. This will return null if the field or term does not exist or positions were not indexed.

Throws:

IOException

See Also:

getTermPositionsEnum(IndexReader, String, BytesRef, int)

getTermPositionsEnum

public static PostingsEnum getTermPositionsEnum(IndexReader r,
                                                String field,
                                                BytesRef term,
                                                int flags)
                                         throws IOException

Returns PostingsEnum for the specified field and term, with control over whether offsets and payloads are required. Some codecs may be able to optimize their implementation when offsets and/or payloads are not required. This will return null if the field or term does not exist. See TermsEnum.postings(PostingsEnum,int).

Throws:

IOException

iterator

public Iterator<String> iterator()

Description copied from class: Fields

Returns an iterator that will step through all fields names. This will not return null.

Specified by:

iterator in interface Iterable<String>

Specified by:

iterator in class Fields

terms

public Terms terms(String field)
            throws IOException

Description copied from class: Fields

Get the Terms for this field. This will return null if the field does not exist.

Specified by:

terms in class Fields

Throws:

IOException

size

public int size()

Description copied from class: Fields

Returns the number of fields or -1 if the number of distinct field names is unknown. If >= 0, Fields.iterator() will return as many field names.

Specified by:

size in class Fields

getMergedFieldInfos

public static FieldInfos getMergedFieldInfos(IndexReader reader)

Call this to get the (merged) FieldInfos for a composite reader.

NOTE: the returned field numbers will likely not correspond to the actual field numbers in the underlying readers, and codec metadata (FieldInfo.getAttribute(String) will be unavailable.

getIndexedFields

public static Collection<String> getIndexedFields(IndexReader reader)

Call this to get the (merged) FieldInfos representing the set of indexed fields only for a composite reader.

NOTE: the returned field numbers will likely not correspond to the actual field numbers in the underlying readers, and codec metadata (FieldInfo.getAttribute(String) will be unavailable.