Class IndexWriter
- All Implemented Interfaces:
Closeable,AutoCloseable,MergePolicy.MergeContext,TwoPhaseCommit,Accountable
IndexWriter creates and maintains an index.
The IndexWriterConfig.OpenMode option on IndexWriterConfig.setOpenMode(OpenMode) determines
whether a new index is created, or whether an existing index is opened. Note that you can open an
index with IndexWriterConfig.OpenMode.CREATE even while readers are using the index. The old readers will
continue to search the "point in time" snapshot they had opened, and won't see the newly created
index until they re-open. If IndexWriterConfig.OpenMode.CREATE_OR_APPEND is used IndexWriter will create a
new index if there is not already an index at the provided path and otherwise open the existing
index.
In either case, documents are added with addDocument and
removed with deleteDocuments(Term...) or deleteDocuments(Query...). A document
can be updated with updateDocument (which just deletes
and then adds the entire document). When finished adding, deleting and updating documents, close should be called.
Each method that changes the index returns a long sequence number, which expresses the
effective order in which each change was applied. commit() also returns a sequence number,
describing which changes are in the commit point and which are not. Sequence numbers are
transient (not saved into the index in any way) and only valid within a single
IndexWriter instance.
These changes are buffered in memory and periodically flushed to the Directory (during
the above method calls). A flush is triggered when there are enough added documents since the
last flush. Flushing is triggered either by RAM usage of the documents (see IndexWriterConfig.setRAMBufferSizeMB(double)) or the number of added documents (see IndexWriterConfig.setMaxBufferedDocs(int)). The default is to flush when RAM usage hits IndexWriterConfig.DEFAULT_RAM_BUFFER_SIZE_MB MB. For best indexing speed you should flush by RAM
usage with a large RAM buffer. In contrast to the other flush options IndexWriterConfig.setRAMBufferSizeMB(double) and IndexWriterConfig.setMaxBufferedDocs(int),
deleted terms won't trigger a segment flush. Note that flushing just moves the internal buffered
state in IndexWriter into the index, but these changes are not visible to IndexReader until
either commit() or close() is called. A flush may also trigger one or more
segment merges which by default run with a background thread so as not to block the addDocument
calls (see below for changing the MergeScheduler).
Opening an IndexWriter creates a lock file for the directory in use. Trying to
open another IndexWriter on the same directory will lead to a LockObtainFailedException.
Expert: IndexWriter allows an optional IndexDeletionPolicy implementation
to be specified. You can use this to control when prior commits are deleted from the index. The
default policy is KeepOnlyLastCommitDeletionPolicy which removes all prior commits as
soon as a new commit is done. Creating your own policy can allow you to explicitly keep previous
"point in time" commits alive in the index for some time, either because this is useful for your
application, or to give readers enough time to refresh to the new commit without having the old
commit deleted out from under them. The latter is necessary when multiple computers take turns
opening their own IndexWriter and IndexReaders against a single shared index
mounted via remote filesystems like NFS which do not support "delete on last close" semantics. A
single computer accessing an index via NFS is fine with the default deletion policy since NFS
clients emulate "delete on last close" locally. That said, accessing an index via NFS will likely
result in poor performance compared to a local IO device.
Expert: IndexWriter allows you to separately change the MergePolicy and
the MergeScheduler. The MergePolicy is invoked whenever there are changes to the
segments in the index. Its role is to select which merges to do, if any, and return a MergePolicy.MergeSpecification describing the merges. The default is LogByteSizeMergePolicy. Then, the MergeScheduler is invoked with the requested merges
and it decides when and how to run the merges. The default is ConcurrentMergeScheduler.
NOTE: if you hit an Error, or disaster strikes during a checkpoint then IndexWriter will close itself. This is a defensive measure in case any internal state (buffered documents, deletions, reference counts) were corrupted. Any subsequent calls will throw an AlreadyClosedException.
NOTE: IndexWriter instances are completely thread safe, meaning multiple
threads can call any of its methods, concurrently. If your application requires external
synchronization, you should not synchronize on the IndexWriter instance as
this may cause deadlock; use your own (non-Lucene) objects instead.
NOTE: If you call Thread.interrupt() on a thread that's within
IndexWriter, IndexWriter will try to catch this (eg, if it's in a wait() or Thread.sleep()), and
will then throw the unchecked exception ThreadInterruptedException and clear the
interrupt status on the thread.
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionstatic final classDocStats for this indexstatic interfaceIfDirectoryReader.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. -
Field Summary
FieldsModifier and TypeFieldDescriptionstatic final intHard limit on maximum number of documents that may be added to the index.static final intMaximum value of the token position in an indexed field.static final intMaximum length string for a stored field.static final intAbsolute hard maximum length for a term, in bytes once encoded as UTF8.static final StringKey for the source of a segment in thediagnostics.static final StringSource of a segment which results from a call toaddIndexes(CodecReader...).static final StringSource of a segment which results from a flush.static final StringSource of a segment which results from a merge of other segments.static final StringName of the write lock in the index.Fields inherited from interface org.apache.lucene.util.Accountable
NULL_ACCOUNTABLE -
Constructor Summary
ConstructorsConstructorDescriptionIndexWriter(Directory d, IndexWriterConfig conf) Constructs a new IndexWriter per the settings given inconf. -
Method Summary
Modifier and TypeMethodDescriptionlongaddDocument(Iterable<? extends IndexableField> doc) Adds a document to this index.longaddDocuments(Iterable<? extends Iterable<? extends IndexableField>> docs) Atomically adds a block of documents with sequentially assigned document IDs, such that an external reader will see all or none of the documents.longaddIndexes(CodecReader... readers) Merges the provided indexes into this index.longaddIndexes(Directory... dirs) Adds all segments from an array of indexes into this index.voidRuns a single merge operation foraddIndexes(CodecReader...).voidadvanceSegmentInfosVersion(long newVersion) IfSegmentInfos.getVersion()is belownewVersionthen update it to this value.voidclose()Closes all open resources and releases the write lock.final longcommit()Commits all pending changes (added and deleted documents, segment merges, added indexes, etc.) to the index, and syncs all referenced index files, such that a reader will see the changes and the index updates will survive an OS or machine crash or power loss.voiddecRefDeleter(SegmentInfos segmentInfos) Record that the files referenced by thisSegmentInfosare no longer in use.longDelete all documents in the index.longdeleteDocuments(Term... terms) Deletes the document(s) containing any of the terms.longdeleteDocuments(Query... queries) Deletes the document(s) matching any of the provided queries.voidExpert: remove any index files that are no longer used.protected voidA hook for extending classes to execute operations after pending added and deleted documents have been flushed to the Directory but before the change is committed (new segments_N file written).protected voidA hook for extending classes to execute operations before pending added and deleted documents are flushed to the Directory.protected final voidUsed internally to throw anAlreadyClosedExceptionif this IndexWriter has been closed (closed=true) or is in the process of closing (closing=true).protected final voidensureOpen(boolean failIfClosing) Used internally to throw anAlreadyClosedExceptionif this IndexWriter has been closed or is in the process of closing.final voidflush()final booleanExpert: Flushes the next pending writer per thread buffer if available or the largest active non-pending writer per thread buffer in the calling thread.voidforceMerge(int maxNumSegments) Forces merge policy to merge segments until there are<= maxNumSegments.voidforceMerge(int maxNumSegments, boolean doWait) Just likeforceMerge(int), except you can specify whether the call should block until all merging completes.voidForces merging of all segments that have deleted documents.voidforceMergeDeletes(boolean doWait) Just likeforceMergeDeletes(), except you can specify whether the call should block until the operation completes.Returns the analyzer used by this index.Returns aLiveIndexWriterConfig, which can be used to query the IndexWriter current settings, as well as modify "live" ones.Returns the Directory used by this index.Returns accurateIndexWriter.DocStatsfor this writer.Return an unmodifiable set of all field names as visible from this IndexWriter, across all segments of the index.final longReturns the number of bytes currently being flushedReturns the info stream that can be used to log messagesReturns the commit user data iterable previously set withsetLiveCommitData(Iterable), or null if nothing has been set yet.longReturns the highest sequence number across all completed operations, or 0 if no operations have finished yet.Expert: to be used by aMergePolicyto avoid selecting merges for segments already being merged.longReturns the number of documents in the index including documents are being added (i.e., reserved).If thisIndexWriterwas closed as a side-effect of a tragic exception, e.g.booleanReturns true if this index has deletions (including buffered deletions).booleanExpert: returns true if there are merges waiting to be scheduled.final booleanReturns true if there may be changes that have not been committed.voidincRefDeleter(SegmentInfos segmentInfos) Record that the files referenced by thisSegmentInfosare still in use.protected booleanTests should override this to enable test points.booleanisOpen()Returnstrueif thisIndexWriteris still open.final voidExpert: asks the mergePolicy whether any merges are necessary now and if so, runs the requested merges and then iterate (test again if merges are needed) until no more merges are returned by the mergePolicy.protected voidmerge(MergePolicy.OneMerge merge) Merges the indicated segments, replacing them in the stack with a single segment.protected voidmergeSuccess(MergePolicy.OneMerge merge) Hook that's called when the specified merge is complete.intObtain the number of deleted docs for a pooled reader.final intReturns the number of deletes a merge would claim back if the given segment is merged.final intExpert: Return the number of documents currently buffered in RAM.voidonTragicEvent(Throwable tragedy, String location) This method should be called on a tragic event ie.final longExpert: prepare for commit.final longReturn the memory usage of this object in bytes.voidrollback()Close theIndexWriterwithout committing any changes that have occurred since the last commit (or since it was opened, if commit hasn't been called).final voidsetLiveCommitData(Iterable<Map.Entry<String, String>> commitUserData) Sets the iterator to provide the commit user data map at commit time.final voidsetLiveCommitData(Iterable<Map.Entry<String, String>> commitUserData, boolean doIncrementVersion) Sets the commit user data iterator, controlling whether to advance theSegmentInfos.getVersion().longsoftUpdateDocument(Term term, Iterable<? extends IndexableField> doc, Field... softDeletes) Expert: Updates a document by first updating the document(s) containingtermwith the given doc-values fields and then adding the new document.longsoftUpdateDocuments(Term term, Iterable<? extends Iterable<? extends IndexableField>> docs, Field... softDeletes) Expert: Atomically updates documents matching the provided term with the given doc-values fields and adds a block of documents with sequentially assigned document IDs, such that an external reader will see all or none of the documents.longtryDeleteDocument(IndexReader readerIn, int docID) Expert: attempts to delete by document ID, as long as the provided reader is a near-real-time reader (fromDirectoryReader.open(IndexWriter)).longtryUpdateDocValue(IndexReader readerIn, int docID, Field... fields) Expert: attempts to update doc values by document ID, as long as the provided reader is a near-real-time reader (fromDirectoryReader.open(IndexWriter)).longupdateBinaryDocValue(Term term, String field, BytesRef value) longupdateDocument(Term term, Iterable<? extends IndexableField> doc) Updates a document by first deleting the document(s) containingtermand then adding the new document.longupdateDocuments(Term delTerm, Iterable<? extends Iterable<? extends IndexableField>> docs) Atomically deletes documents matching the provided delTerm and adds a block of documents with sequentially assigned document IDs, such that an external reader will see all or none of the documents.longupdateDocuments(Query delQuery, Iterable<? extends Iterable<? extends IndexableField>> docs) Similar toupdateDocuments(Term, Iterable), but take a query instead of a term to identify the documents to be updatedlongupdateDocValues(Term term, Field... updates) Updates documents' DocValues fields to the given values.longupdateNumericDocValue(Term term, String field, long value) Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, waitMethods inherited from interface org.apache.lucene.util.Accountable
getChildResources
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Field Details
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MAX_DOCS
public static final int MAX_DOCSHard limit on maximum number of documents that may be added to the index. If you try to add more than this you'll hitIllegalArgumentException.- See Also:
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MAX_POSITION
public static final int MAX_POSITIONMaximum value of the token position in an indexed field.- See Also:
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WRITE_LOCK_NAME
Name of the write lock in the index.- See Also:
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SOURCE
Key for the source of a segment in thediagnostics.- See Also:
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SOURCE_MERGE
Source of a segment which results from a merge of other segments.- See Also:
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SOURCE_FLUSH
Source of a segment which results from a flush.- See Also:
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SOURCE_ADDINDEXES_READERS
Source of a segment which results from a call toaddIndexes(CodecReader...).- See Also:
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MAX_TERM_LENGTH
public static final int MAX_TERM_LENGTHAbsolute hard maximum length for a term, in bytes once encoded as UTF8. If a term arrives from the analyzer longer than this length, anIllegalArgumentExceptionis thrown and a message is printed to infoStream, if set (seeIndexWriterConfig.setInfoStream(InfoStream)).- See Also:
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MAX_STORED_STRING_LENGTH
public static final int MAX_STORED_STRING_LENGTHMaximum length string for a stored field.
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Constructor Details
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IndexWriter
Constructs a new IndexWriter per the settings given inconf. If you want to make "live" changes to this writer instance, usegetConfig().NOTE: after ths writer is created, the given configuration instance cannot be passed to another writer.
- Parameters:
d- the index directory. The index is either created or appended accordingconf.getOpenMode().conf- the configuration settings according to which IndexWriter should be initialized.- Throws:
IOException- if the directory cannot be read/written to, or if it does not exist andconf.getOpenMode()isOpenMode.APPENDor if there is any other low-level IO error
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Method Details
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ramBytesUsed
public final long ramBytesUsed()Description copied from interface:AccountableReturn the memory usage of this object in bytes. Negative values are illegal.- Specified by:
ramBytesUsedin interfaceAccountable
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getFlushingBytes
public final long getFlushingBytes()Returns the number of bytes currently being flushed -
numDeletedDocs
Obtain the number of deleted docs for a pooled reader. If the reader isn't being pooled, the segmentInfo's delCount is returned.- Specified by:
numDeletedDocsin interfaceMergePolicy.MergeContext
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ensureOpen
Used internally to throw anAlreadyClosedExceptionif this IndexWriter has been closed or is in the process of closing.- Parameters:
failIfClosing- if true, also fail whenIndexWriteris in the process of closing (closing=true) but not yet done closing (closed=false)- Throws:
AlreadyClosedException- if this IndexWriter is closed or in the process of closing
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ensureOpen
Used internally to throw anAlreadyClosedExceptionif this IndexWriter has been closed (closed=true) or is in the process of closing (closing=true).Calls
ensureOpen(true).- Throws:
AlreadyClosedException- if this IndexWriter is closed
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getConfig
Returns aLiveIndexWriterConfig, which can be used to query the IndexWriter current settings, as well as modify "live" ones. -
close
Closes all open resources and releases the write lock.If
LiveIndexWriterConfig.commitOnCloseistrue, this will attempt to gracefully shut down by writing any changes, waiting for any running merges, committing, and closing. In this case, note that:- If you called prepareCommit but failed to call commit, this method will throw
IllegalStateExceptionand theIndexWriterwill not be closed. - If this method throws any other exception, the
IndexWriterwill be closed, but changes may have been lost.
Note that this may be a costly operation, so, try to re-use a single writer instead of closing and opening a new one. See
commit()for caveats about write caching done by some IO devices.NOTE: You must ensure no other threads are still making changes at the same time that this method is invoked.
- Specified by:
closein interfaceAutoCloseable- Specified by:
closein interfaceCloseable- Throws:
IOException
- If you called prepareCommit but failed to call commit, this method will throw
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getDirectory
Returns the Directory used by this index. -
getInfoStream
Description copied from interface:MergePolicy.MergeContextReturns the info stream that can be used to log messages- Specified by:
getInfoStreamin interfaceMergePolicy.MergeContext
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getAnalyzer
Returns the analyzer used by this index. -
advanceSegmentInfosVersion
public void advanceSegmentInfosVersion(long newVersion) IfSegmentInfos.getVersion()is belownewVersionthen update it to this value.- NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.
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hasDeletions
public boolean hasDeletions()Returns true if this index has deletions (including buffered deletions). Note that this will return true if there are buffered Term/Query deletions, even if it turns out those buffered deletions don't match any documents. -
addDocument
Adds a document to this index.Note that if an Exception is hit (for example disk full) then the index will be consistent, but this document may not have been added. Furthermore, it's possible the index will have one segment in non-compound format even when using compound files (when a merge has partially succeeded).
This method periodically flushes pending documents to the Directory (see above), and also periodically triggers segment merges in the index according to the
MergePolicyin use.Merges temporarily consume space in the directory. The amount of space required is up to 1X the size of all segments being merged, when no readers/searchers are open against the index, and up to 2X the size of all segments being merged when readers/searchers are open against the index (see
forceMerge(int)for details). The sequence of primitive merge operations performed is governed by the merge policy.Note that each term in the document can be no longer than
MAX_TERM_LENGTHin bytes, otherwise an IllegalArgumentException will be thrown.Note that it's possible to create an invalid Unicode string in java if a UTF16 surrogate pair is malformed. In this case, the invalid characters are silently replaced with the Unicode replacement character U+FFFD.
- Returns:
- The sequence number for this operation
- Throws:
CorruptIndexException- if the index is corruptIOException- if there is a low-level IO error
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addDocuments
public long addDocuments(Iterable<? extends Iterable<? extends IndexableField>> docs) throws IOException Atomically adds a block of documents with sequentially assigned document IDs, such that an external reader will see all or none of the documents.WARNING: the index does not currently record which documents were added as a block. Today this is fine, because merging will preserve a block. The order of documents within a segment will be preserved, even when child documents within a block are deleted. Most search features (like result grouping and block joining) require you to mark documents; when these documents are deleted these search features will not work as expected. Obviously adding documents to an existing block will require you the reindex the entire block.
However it's possible that in the future Lucene may merge more aggressively re-order documents (for example, perhaps to obtain better index compression), in which case you may need to fully re-index your documents at that time.
See
addDocument(Iterable)for details on index and IndexWriter state after an Exception, and flushing/merging temporary free space requirements.NOTE: tools that do offline splitting of an index (for example, IndexSplitter in contrib) or re-sorting of documents (for example, IndexSorter in contrib) are not aware of these atomically added documents and will likely break them up. Use such tools at your own risk!
- Returns:
- The sequence number for this operation
- Throws:
CorruptIndexException- if the index is corruptIOException- if there is a low-level IO error- WARNING: This API is experimental and might change in incompatible ways in the next release.
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updateDocuments
public long updateDocuments(Term delTerm, Iterable<? extends Iterable<? extends IndexableField>> docs) throws IOException Atomically deletes documents matching the provided delTerm and adds a block of documents with sequentially assigned document IDs, such that an external reader will see all or none of the documents.- Returns:
- The sequence number for this operation
- Throws:
CorruptIndexException- if the index is corruptIOException- if there is a low-level IO error- WARNING: This API is experimental and might change in incompatible ways in the next release.
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updateDocuments
public long updateDocuments(Query delQuery, Iterable<? extends Iterable<? extends IndexableField>> docs) throws IOException Similar toupdateDocuments(Term, Iterable), but take a query instead of a term to identify the documents to be updated- Throws:
IOException- WARNING: This API is experimental and might change in incompatible ways in the next release.
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softUpdateDocuments
public long softUpdateDocuments(Term term, Iterable<? extends Iterable<? extends IndexableField>> docs, Field... softDeletes) throws IOException Expert: Atomically updates documents matching the provided term with the given doc-values fields and adds a block of documents with sequentially assigned document IDs, such that an external reader will see all or none of the documents.One use of this API is to retain older versions of documents instead of replacing them. The existing documents can be updated to reflect they are no longer current while atomically adding new documents at the same time.
In contrast to
updateDocuments(Term, Iterable)this method will not delete documents in the index matching the given term but instead update them with the given doc-values fields which can be used as a soft-delete mechanism.See
addDocuments(Iterable)andupdateDocuments(Term, Iterable).- Returns:
- The sequence number for this operation
- Throws:
CorruptIndexException- if the index is corruptIOException- if there is a low-level IO error- WARNING: This API is experimental and might change in incompatible ways in the next release.
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tryDeleteDocument
Expert: attempts to delete by document ID, as long as the provided reader is a near-real-time reader (fromDirectoryReader.open(IndexWriter)). If the provided reader is an NRT reader obtained from this writer, and its segment has not been merged away, then the delete succeeds and this method returns a valid (> 0) sequence number; else, it returns -1 and the caller must then separately delete by Term or Query.NOTE: this method can only delete documents visible to the currently open NRT reader. If you need to delete documents indexed after opening the NRT reader you must use
deleteDocuments(Term...)).- Throws:
IOException
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tryUpdateDocValue
Expert: attempts to update doc values by document ID, as long as the provided reader is a near-real-time reader (fromDirectoryReader.open(IndexWriter)). If the provided reader is an NRT reader obtained from this writer, and its segment has not been merged away, then the update succeeds and this method returns a valid (> 0) sequence number; else, it returns -1 and the caller must then either retry the update and resolve the document again. If a doc values fields data isnullthe existing value is removed from all documents matching the term. This can be used to un-delete a soft-deleted document since this method will apply the field update even if the document is marked as deleted.NOTE: this method can only updates documents visible to the currently open NRT reader. If you need to update documents indexed after opening the NRT reader you must use
updateDocValues(Term, Field...).- Throws:
IOException
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deleteDocuments
Deletes the document(s) containing any of the terms. All given deletes are applied and flushed atomically at the same time.- Parameters:
terms- array of terms to identify the documents to be deleted- Returns:
- The sequence number for this operation
- Throws:
CorruptIndexException- if the index is corruptIOException- if there is a low-level IO error
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deleteDocuments
Deletes the document(s) matching any of the provided queries. All given deletes are applied and flushed atomically at the same time.- Parameters:
queries- array of queries to identify the documents to be deleted- Returns:
- The sequence number for this operation
- Throws:
CorruptIndexException- if the index is corruptIOException- if there is a low-level IO error
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updateDocument
Updates a document by first deleting the document(s) containingtermand then adding the new document. The delete and then add are atomic as seen by a reader on the same index (flush may happen only after the add).- Parameters:
term- the term to identify the document(s) to be deleteddoc- the document to be added- Returns:
- The sequence number for this operation
- Throws:
CorruptIndexException- if the index is corruptIOException- if there is a low-level IO error
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softUpdateDocument
public long softUpdateDocument(Term term, Iterable<? extends IndexableField> doc, Field... softDeletes) throws IOException Expert: Updates a document by first updating the document(s) containingtermwith the given doc-values fields and then adding the new document. The doc-values update and then add are atomic as seen by a reader on the same index (flush may happen only after the add).One use of this API is to retain older versions of documents instead of replacing them. The existing documents can be updated to reflect they are no longer current while atomically adding new documents at the same time.
In contrast to
updateDocument(Term, Iterable)this method will not delete documents in the index matching the given term but instead update them with the given doc-values fields which can be used as a soft-delete mechanism.See
addDocuments(Iterable)andupdateDocuments(Term, Iterable).- Returns:
- The sequence number for this operation
- Throws:
CorruptIndexException- if the index is corruptIOException- if there is a low-level IO error- WARNING: This API is experimental and might change in incompatible ways in the next release.
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updateNumericDocValue
Updates a document'sNumericDocValuesforfieldto the givenvalue. You can only update fields that already exist in the index, not add new fields through this method. You can only update fields that were indexed with doc values only.- Parameters:
term- the term to identify the document(s) to be updatedfield- field name of theNumericDocValuesfieldvalue- new value for the field- Returns:
- The sequence number for this operation
- Throws:
CorruptIndexException- if the index is corruptIOException- if there is a low-level IO error
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updateBinaryDocValue
Updates a document'sBinaryDocValuesforfieldto the givenvalue. You can only update fields that already exist in the index, not add new fields through this method. You can only update fields that were indexed only with doc values.NOTE: this method currently replaces the existing value of all affected documents with the new value.
- Parameters:
term- the term to identify the document(s) to be updatedfield- field name of theBinaryDocValuesfieldvalue- new value for the field- Returns:
- The sequence number for this operation
- Throws:
CorruptIndexException- if the index is corruptIOException- if there is a low-level IO error
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updateDocValues
Updates documents' DocValues fields to the given values. Each field update is applied to the set of documents that are associated with theTermto the same value. All updates are atomically applied and flushed together. If a doc values fields data isnullthe existing value is removed from all documents matching the term.- Parameters:
updates- the updates to apply- Returns:
- The sequence number for this operation
- Throws:
CorruptIndexException- if the index is corruptIOException- if there is a low-level IO error
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getFieldNames
Return an unmodifiable set of all field names as visible from this IndexWriter, across all segments of the index.- WARNING: This API is experimental and might change in incompatible ways in the next release.
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forceMerge
Forces merge policy to merge segments until there are<= maxNumSegments. The actual merges to be executed are determined by theMergePolicy.This is a horribly costly operation, especially when you pass a small
maxNumSegments; usually you should only call this if the index is static (will no longer be changed).Note that this requires free space that is proportional to the size of the index in your Directory: 2X if you are not using compound file format, and 3X if you are. For example, if your index size is 10 MB then you need an additional 20 MB free for this to complete (30 MB if you're using compound file format). This is also affected by the
Codecthat is used to execute the merge, and may result in even a bigger index. Also, it's best to callcommit()afterwards, to allow IndexWriter to free up disk space.If some but not all readers re-open while merging is underway, this will cause
> 2Xtemporary space to be consumed as those new readers will then hold open the temporary segments at that time. It is best not to re-open readers while merging is running.The actual temporary usage could be much less than these figures (it depends on many factors).
In general, once this completes, the total size of the index will be less than the size of the starting index. It could be quite a bit smaller (if there were many pending deletes) or just slightly smaller.
If an Exception is hit, for example due to disk full, the index will not be corrupted and no documents will be lost. However, it may have been partially merged (some segments were merged but not all), and it's possible that one of the segments in the index will be in non-compound format even when using compound file format. This will occur when the Exception is hit during conversion of the segment into compound format.
This call will merge those segments present in the index when the call started. If other threads are still adding documents and flushing segments, those newly created segments will not be merged unless you call forceMerge again.
- Parameters:
maxNumSegments- maximum number of segments left in the index after merging finishes- Throws:
CorruptIndexException- if the index is corruptIOException- if there is a low-level IO error- See Also:
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forceMerge
Just likeforceMerge(int), except you can specify whether the call should block until all merging completes. This is only meaningful with aMergeSchedulerthat is able to run merges in background threads.- Throws:
IOException
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forceMergeDeletes
Just likeforceMergeDeletes(), except you can specify whether the call should block until the operation completes. This is only meaningful with aMergeSchedulerthat is able to run merges in background threads.- Throws:
IOException
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forceMergeDeletes
Forces merging of all segments that have deleted documents. The actual merges to be executed are determined by theMergePolicy. For example, the defaultTieredMergePolicywill only pick a segment if the percentage of deleted docs is over 10%.This is often a horribly costly operation; rarely is it warranted.
To see how many deletions you have pending in your index, call
IndexReader.numDeletedDocs().NOTE: this method first flushes a new segment (if there are indexed documents), and applies all buffered deletes.
- Throws:
IOException
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maybeMerge
Expert: asks the mergePolicy whether any merges are necessary now and if so, runs the requested merges and then iterate (test again if merges are needed) until no more merges are returned by the mergePolicy.Explicit calls to maybeMerge() are usually not necessary. The most common case is when merge policy parameters have changed.
This method will call the
MergePolicywithMergeTrigger.EXPLICIT.- Throws:
IOException
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getMergingSegments
Expert: to be used by aMergePolicyto avoid selecting merges for segments already being merged. The returned collection is not cloned, and thus is only safe to access if you hold IndexWriter's lock (which you do when IndexWriter invokes the MergePolicy).The Set is unmodifiable.
- Specified by:
getMergingSegmentsin interfaceMergePolicy.MergeContext
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hasPendingMerges
public boolean hasPendingMerges()Expert: returns true if there are merges waiting to be scheduled.- WARNING: This API is experimental and might change in incompatible ways in the next release.
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rollback
Close theIndexWriterwithout committing any changes that have occurred since the last commit (or since it was opened, if commit hasn't been called). This removes any temporary files that had been created, after which the state of the index will be the same as it was when commit() was last called or when this writer was first opened. This also clears a previous call toprepareCommit().- Specified by:
rollbackin interfaceTwoPhaseCommit- Throws:
IOException- if there is a low-level IO error
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deleteAll
Delete all documents in the index.This method will drop all buffered documents and will remove all segments from the index. This change will not be visible until a
commit()has been called. This method can be rolled back usingrollback().NOTE: this method is much faster than using deleteDocuments( new MatchAllDocsQuery() ). Yet, this method also has different semantics compared to
deleteDocuments(Query...)since internal data-structures are cleared as well as all segment information is forcefully dropped anti-viral semantics like omitting norms are reset or doc value types are cleared. Essentially a call todeleteAll()is equivalent to creating a newIndexWriterwithIndexWriterConfig.OpenMode.CREATEwhich a delete query only marks documents as deleted.NOTE: this method will forcefully abort all merges in progress. If other threads are running
forceMerge(int),addIndexes(CodecReader[])orforceMergeDeletes(boolean)methods, they may receiveMergePolicy.MergeAbortedExceptions.- Returns:
- The sequence number for this operation
- Throws:
IOException
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addIndexes
Adds all segments from an array of indexes into this index.This may be used to parallelize batch indexing. A large document collection can be broken into sub-collections. Each sub-collection can be indexed in parallel, on a different thread, process or machine. The complete index can then be created by merging sub-collection indexes with this method.
NOTE: this method acquires the write lock in each directory, to ensure that no
IndexWriteris currently open or tries to open while this is running.This method is transactional in how Exceptions are handled: it does not commit a new segments_N file until all indexes are added. This means if an Exception occurs (for example disk full), then either no indexes will have been added or they all will have been.
Note that this requires temporary free space in the
Directoryup to 2X the sum of all input indexes (including the starting index). If readers/searchers are open against the starting index, then temporary free space required will be higher by the size of the starting index (seeforceMerge(int)for details).This requires this index not be among those to be added.
All added indexes must have been created by the same Lucene version as this index.
- Returns:
- The sequence number for this operation
- Throws:
CorruptIndexException- if the index is corruptIOException- if there is a low-level IO errorIllegalArgumentException- if addIndexes would cause the index to exceedMAX_DOCS, or if the indoming index sort does not match this index's index sort
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addIndexes
Merges the provided indexes into this index.The provided IndexReaders are not closed.
See
addIndexes(org.apache.lucene.store.Directory...)for details on transactional semantics, temporary free space required in the Directory, and non-CFS segments on an Exception.NOTE: empty segments are dropped by this method and not added to this index.
NOTE: provided
LeafReaders are merged as specified by theMergePolicy.findMerges(CodecReader...)API. Default behavior is to merge all provided readers into a single segment. You can modify this by overriding thefindMergeAPI in your custom merge policy.- Returns:
- The sequence number for this operation
- Throws:
CorruptIndexException- if the index is corruptIOException- if there is a low-level IO errorIllegalArgumentException- if addIndexes would cause the index to exceedMAX_DOCS
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addIndexesReaderMerge
Runs a single merge operation foraddIndexes(CodecReader...).Merges and creates a SegmentInfo, for the readers grouped together in provided OneMerge.
- Parameters:
merge- OneMerge object initialized from readers.- Throws:
IOException- if there is a low-level IO error
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doAfterFlush
A hook for extending classes to execute operations after pending added and deleted documents have been flushed to the Directory but before the change is committed (new segments_N file written).- Throws:
IOException
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doBeforeFlush
A hook for extending classes to execute operations before pending added and deleted documents are flushed to the Directory.- Throws:
IOException
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prepareCommit
Expert: prepare for commit. This does the first phase of 2-phase commit. This method does all steps necessary to commit changes since this writer was opened: flushes pending added and deleted docs, syncs the index files, writes most of next segments_N file. After calling this you must call eithercommit()to finish the commit, orrollback()to revert the commit and undo all changes done since the writer was opened.You can also just call
commit()directly without prepareCommit first in which case that method will internally call prepareCommit.- Specified by:
prepareCommitin interfaceTwoPhaseCommit- Returns:
- The sequence number of the last operation in the commit. All sequence numbers <= this value will be reflected in the commit, and all others will not.
- Throws:
IOException
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flushNextBuffer
Expert: Flushes the next pending writer per thread buffer if available or the largest active non-pending writer per thread buffer in the calling thread. This can be used to flush documents to disk outside of an indexing thread. In contrast toflush()this won't mark all currently active indexing buffers as flush-pending.Note: this method is best-effort and might not flush any segments to disk. If there is a full flush happening concurrently multiple segments might have been flushed. Users of this API can access the IndexWriters current memory consumption via
ramBytesUsed()- Returns:
trueiff this method flushed at least on segment to disk.- Throws:
IOException- WARNING: This API is experimental and might change in incompatible ways in the next release.
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setLiveCommitData
Sets the iterator to provide the commit user data map at commit time. Calling this method is considered a committable change and will becommittedeven if there are no other changes this writer. Note that you must call this method beforeprepareCommit(). Otherwise it won't be included in the follow-oncommit().NOTE: the iterator is late-binding: it is only visited once all documents for the commit have been written to their segments, before the next segments_N file is written
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setLiveCommitData
public final void setLiveCommitData(Iterable<Map.Entry<String, String>> commitUserData, boolean doIncrementVersion) Sets the commit user data iterator, controlling whether to advance theSegmentInfos.getVersion().- See Also:
- NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.
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getLiveCommitData
Returns the commit user data iterable previously set withsetLiveCommitData(Iterable), or null if nothing has been set yet. -
commit
Commits all pending changes (added and deleted documents, segment merges, added indexes, etc.) to the index, and syncs all referenced index files, such that a reader will see the changes and the index updates will survive an OS or machine crash or power loss. Note that this does not wait for any running background merges to finish. This may be a costly operation, so you should test the cost in your application and do it only when really necessary.Note that this operation calls Directory.sync on the index files. That call should not return until the file contents and metadata are on stable storage. For FSDirectory, this calls the OS's fsync. But, beware: some hardware devices may in fact cache writes even during fsync, and return before the bits are actually on stable storage, to give the appearance of faster performance. If you have such a device, and it does not have a battery backup (for example) then on power loss it may still lose data. Lucene cannot guarantee consistency on such devices.
If nothing was committed, because there were no pending changes, this returns -1. Otherwise, it returns the sequence number such that all indexing operations prior to this sequence will be included in the commit point, and all other operations will not.
- Specified by:
commitin interfaceTwoPhaseCommit- Returns:
- The sequence number of the last operation in the commit. All sequence numbers <= this value will be reflected in the commit, and all others will not.
- Throws:
IOException- See Also:
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hasUncommittedChanges
public final boolean hasUncommittedChanges()Returns true if there may be changes that have not been committed. There are cases where this may return true when there are no actual "real" changes to the index, for example if you've deleted by Term or Query but that Term or Query does not match any documents. Also, if a merge kicked off as a result of flushing a new segment duringcommit(), or a concurrent merged finished, this method may return true right after you had just calledcommit(). -
flush
Moves all in-memory segments to theDirectory, but does not commit (fsync) them (callcommit()for that).- Throws:
IOException
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numRamDocs
public final int numRamDocs()Expert: Return the number of documents currently buffered in RAM. -
merge
Merges the indicated segments, replacing them in the stack with a single segment.- Throws:
IOException- WARNING: This API is experimental and might change in incompatible ways in the next release.
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mergeSuccess
Hook that's called when the specified merge is complete. -
onTragicEvent
This method should be called on a tragic event ie. if a downstream class of the writer hits an unrecoverable exception. This method does not rethrow the tragic event exception.Note: This method will not close the writer but can be called from any location without respecting any lock order
- NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.
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getTragicException
If thisIndexWriterwas closed as a side-effect of a tragic exception, e.g. disk full while flushing a new segment, this returns the root cause exception. Otherwise (no tragic exception has occurred) it returns null. -
isOpen
public boolean isOpen()Returnstrueif thisIndexWriteris still open. -
deleteUnusedFiles
Expert: remove any index files that are no longer used.IndexWriter normally deletes unused files itself, during indexing. However, on Windows, which disallows deletion of open files, if there is a reader open on the index then those files cannot be deleted. This is fine, because IndexWriter will periodically retry the deletion.
However, IndexWriter doesn't try that often: only on open, close, flushing a new segment, and finishing a merge. If you don't do any of these actions with your IndexWriter, you'll see the unused files linger. If that's a problem, call this method to delete them (once you've closed the open readers that were preventing their deletion).
In addition, you can call this method to delete unreferenced index commits. This might be useful if you are using an
IndexDeletionPolicywhich holds onto index commits until some criteria are met, but those commits are no longer needed. Otherwise, those commits will be deleted the next time commit() is called.- Throws:
IOException
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incRefDeleter
Record that the files referenced by thisSegmentInfosare still in use.- Throws:
IOException- NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.
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decRefDeleter
Record that the files referenced by thisSegmentInfosare no longer in use. Only call this if you are sure you previously calledincRefDeleter(org.apache.lucene.index.SegmentInfos).- Throws:
IOException- NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.
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getPendingNumDocs
public long getPendingNumDocs()Returns the number of documents in the index including documents are being added (i.e., reserved).- WARNING: This API is experimental and might change in incompatible ways in the next release.
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getMaxCompletedSequenceNumber
public long getMaxCompletedSequenceNumber()Returns the highest sequence number across all completed operations, or 0 if no operations have finished yet. Still in-flight operations (in other threads) are not counted until they finish.- WARNING: This API is experimental and might change in incompatible ways in the next release.
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numDeletesToMerge
Returns the number of deletes a merge would claim back if the given segment is merged.- Specified by:
numDeletesToMergein interfaceMergePolicy.MergeContext- Parameters:
info- the segment to get the number of deletes for- Throws:
IOException- See Also:
- WARNING: This API is experimental and might change in incompatible ways in the next release.
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isEnableTestPoints
protected boolean isEnableTestPoints()Tests should override this to enable test points. Default isfalse. -
getDocStats
Returns accurateIndexWriter.DocStatsfor this writer. The numDoc for instance can change after maxDoc is fetched that causes numDocs to be greater than maxDoc which makes it hard to get accurate document stats from IndexWriter.
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