Class IndexWriter

  • All Implemented Interfaces:
    Closeable, AutoCloseable, TwoPhaseCommit

    public class IndexWriter
    extends Object
    implements Closeable, TwoPhaseCommit
    An IndexWriter creates and maintains an index.

    The create argument to the constructor determines whether a new index is created, or whether an existing index is opened. Note that you can open an index with create=true 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. There are also constructors with no create argument which 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.

    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 buffered deletes (see setMaxBufferedDeleteTerms(int)) or enough added documents since the last flush, whichever is sooner. For the added documents, flushing is triggered either by RAM usage of the documents (see setRAMBufferSizeMB(double)) or the number of added documents. The default is to flush when RAM usage hits 16 MB. For best indexing speed you should flush by RAM usage with a large RAM buffer. 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. The LockObtainFailedException is also thrown if an IndexReader on the same directory is used to delete documents from the index.

    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 (this matches behavior before 2.2). Creating your own policy can allow you to explicitly keep previous "point in time" commits alive in the index for some time, to allow readers to refresh to the new commit without having the old commit deleted out from under them. This is necessary on filesystems like NFS that do not support "delete on last close" semantics, which Lucene's "point in time" search normally relies on.

    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 OutOfMemoryError then IndexWriter will quietly record this fact and block all future segment commits. This is a defensive measure in case any internal state (buffered documents and deletions) were corrupted. Any subsequent calls to commit() will throw an IllegalStateException. The only course of action is to call close(), which internally will call rollback(), to undo any changes to the index since the last commit. You can also just call rollback() directly.

    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.

    • Method Detail

      • getReader

        @Deprecated
        public IndexReader getReader()
                              throws IOException
        Deprecated.
        Expert: returns a readonly reader, covering all committed as well as un-committed changes to the index. This provides "near real-time" searching, in that changes made during an IndexWriter session can be quickly made available for searching without closing the writer nor calling commit().

        Note that this is functionally equivalent to calling {#flush} and then using IndexReader.open(org.apache.lucene.store.Directory) to open a new reader. But the turarnound time of this method should be faster since it avoids the potentially costly commit().

        You must close the IndexReader returned by this method once you are done using it.

        It's near real-time because there is no hard guarantee on how quickly you can get a new reader after making changes with IndexWriter. You'll have to experiment in your situation to determine if it's fast enough. As this is a new and experimental feature, please report back on your findings so we can learn, improve and iterate.

        The resulting reader supports IndexReader.reopen(), but that call will simply forward back to this method (though this may change in the future).

        The very first time this method is called, this writer instance will make every effort to pool the readers that it opens for doing merges, applying deletes, etc. This means additional resources (RAM, file descriptors, CPU time) will be consumed.

        For lower latency on reopening a reader, you should call setMergedSegmentWarmer(org.apache.lucene.index.IndexWriter.IndexReaderWarmer) to pre-warm a newly merged segment before it's committed to the index. This is important for minimizing index-to-search delay after a large merge.

        If an addIndexes* call is running in another thread, then this reader will only search those segments from the foreign index that have been successfully copied over, so far

        .

        NOTE: Once the writer is closed, any outstanding readers may continue to be used. However, if you attempt to reopen any of those readers, you'll hit an AlreadyClosedException.

        Returns:
        IndexReader that covers entire index plus all changes made so far by this IndexWriter instance
        Throws:
        IOException
        WARNING: This API is experimental and might change in incompatible ways in the next release.
      • getReader

        @Deprecated
        public IndexReader getReader​(int termInfosIndexDivisor)
                              throws IOException
        Deprecated.
        Please use IndexReader.open(IndexWriter,boolean) instead. Furthermore, this method cannot guarantee the reader (and its sub-readers) will be opened with the termInfosIndexDivisor setting because some of them may have already been opened according to IndexWriterConfig.setReaderTermsIndexDivisor(int). You should set the requested termInfosIndexDivisor through IndexWriterConfig.setReaderTermsIndexDivisor(int) and use getReader().
        Expert: like getReader(), except you can specify which termInfosIndexDivisor should be used for any newly opened readers.
        Parameters:
        termInfosIndexDivisor - Subsamples which indexed terms are loaded into RAM. This has the same effect as setTermIndexInterval(int) except that setting must be done at indexing time while this setting can be set per reader. When set to N, then one in every N*termIndexInterval terms in the index is loaded into memory. By setting this to a value > 1 you can reduce memory usage, at the expense of higher latency when loading a TermInfo. The default value is 1. Set this to -1 to skip loading the terms index entirely.
        Throws:
        IOException
      • numDeletedDocs

        public int numDeletedDocs​(SegmentInfo info)
                           throws IOException
        Obtain the number of deleted docs for a pooled reader. If the reader isn't being pooled, the segmentInfo's delCount is returned.
        Throws:
        IOException
      • message

        public void message​(String message)
        Prints a message to the infoStream (if non-null), prefixed with the identifying information for this writer and the thread that's calling it.
      • getUseCompoundFile

        @Deprecated
        public boolean getUseCompoundFile()

        Get the current setting of whether newly flushed segments will use the compound file format. Note that this just returns the value previously set with setUseCompoundFile(boolean), or the default value (true). You cannot use this to query the status of previously flushed segments.

        Note that this method is a convenience method: it just calls mergePolicy.getUseCompoundFile as long as mergePolicy is an instance of LogMergePolicy. Otherwise an IllegalArgumentException is thrown.

        See Also:
        setUseCompoundFile(boolean)
      • setUseCompoundFile

        @Deprecated
        public void setUseCompoundFile​(boolean value)

        Setting to turn on usage of a compound file. When on, multiple files for each segment are merged into a single file when a new segment is flushed.

        Note that this method is a convenience method: it just calls mergePolicy.setUseCompoundFile as long as mergePolicy is an instance of LogMergePolicy. Otherwise an IllegalArgumentException is thrown.

      • setTermIndexInterval

        @Deprecated
        public void setTermIndexInterval​(int interval)
        Expert: Set the interval between indexed terms. Large values cause less memory to be used by IndexReader, but slow random-access to terms. Small values cause more memory to be used by an IndexReader, and speed random-access to terms. This parameter determines the amount of computation required per query term, regardless of the number of documents that contain that term. In particular, it is the maximum number of other terms that must be scanned before a term is located and its frequency and position information may be processed. In a large index with user-entered query terms, query processing time is likely to be dominated not by term lookup but rather by the processing of frequency and positional data. In a small index or when many uncommon query terms are generated (e.g., by wildcard queries) term lookup may become a dominant cost. In particular, numUniqueTerms/interval terms are read into memory by an IndexReader, and, on average, interval/2 terms must be scanned for each random term access.
        See Also:
        DEFAULT_TERM_INDEX_INTERVAL
      • setMaxMergeDocs

        @Deprecated
        public void setMaxMergeDocs​(int maxMergeDocs)
        Deprecated.

        Determines the largest segment (measured by document count) that may be merged with other segments. Small values (e.g., less than 10,000) are best for interactive indexing, as this limits the length of pauses while indexing to a few seconds. Larger values are best for batched indexing and speedier searches.

        The default value is Integer.MAX_VALUE.

        Note that this method is a convenience method: it just calls mergePolicy.setMaxMergeDocs as long as mergePolicy is an instance of LogMergePolicy. Otherwise an IllegalArgumentException is thrown.

        The default merge policy (LogByteSizeMergePolicy) also allows you to set this limit by net size (in MB) of the segment, using LogByteSizeMergePolicy.setMaxMergeMB(double).

      • getMaxMergeDocs

        @Deprecated
        public int getMaxMergeDocs()
        Deprecated.

        Returns the largest segment (measured by document count) that may be merged with other segments.

        Note that this method is a convenience method: it just calls mergePolicy.getMaxMergeDocs as long as mergePolicy is an instance of LogMergePolicy. Otherwise an IllegalArgumentException is thrown.

        See Also:
        setMaxMergeDocs(int)
      • setMaxFieldLength

        @Deprecated
        public void setMaxFieldLength​(int maxFieldLength)
        Deprecated.
        use LimitTokenCountAnalyzer instead. Note that the behvaior slightly changed - the analyzer limits the number of tokens per token stream created, while this setting limits the total number of tokens to index. This only matters if you index many multi-valued fields though.
        The maximum number of terms that will be indexed for a single field in a document. This limits the amount of memory required for indexing, so that collections with very large files will not crash the indexing process by running out of memory. This setting refers to the number of running terms, not to the number of different terms.

        Note: this silently truncates large documents, excluding from the index all terms that occur further in the document. If you know your source documents are large, be sure to set this value high enough to accomodate the expected size. If you set it to Integer.MAX_VALUE, then the only limit is your memory, but you should anticipate an OutOfMemoryError.

        By default, no more than DEFAULT_MAX_FIELD_LENGTH terms will be indexed for a field.

      • setMaxBufferedDocs

        @Deprecated
        public void setMaxBufferedDocs​(int maxBufferedDocs)
        Determines the minimal number of documents required before the buffered in-memory documents are flushed as a new Segment. Large values generally gives faster indexing.

        When this is set, the writer will flush every maxBufferedDocs added documents. Pass in DISABLE_AUTO_FLUSH to prevent triggering a flush due to number of buffered documents. Note that if flushing by RAM usage is also enabled, then the flush will be triggered by whichever comes first.

        Disabled by default (writer flushes by RAM usage).

        Throws:
        IllegalArgumentException - if maxBufferedDocs is enabled but smaller than 2, or it disables maxBufferedDocs when ramBufferSize is already disabled
        See Also:
        setRAMBufferSizeMB(double)
      • setRAMBufferSizeMB

        @Deprecated
        public void setRAMBufferSizeMB​(double mb)
        Determines the amount of RAM that may be used for buffering added documents and deletions before they are flushed to the Directory. Generally for faster indexing performance it's best to flush by RAM usage instead of document count and use as large a RAM buffer as you can.

        When this is set, the writer will flush whenever buffered documents and deletions use this much RAM. Pass in DISABLE_AUTO_FLUSH to prevent triggering a flush due to RAM usage. Note that if flushing by document count is also enabled, then the flush will be triggered by whichever comes first.

        NOTE: the account of RAM usage for pending deletions is only approximate. Specifically, if you delete by Query, Lucene currently has no way to measure the RAM usage if individual Queries so the accounting will under-estimate and you should compensate by either calling commit() periodically yourself, or by using setMaxBufferedDeleteTerms(int) to flush by count instead of RAM usage (each buffered delete Query counts as one).

        NOTE: because IndexWriter uses ints when managing its internal storage, the absolute maximum value for this setting is somewhat less than 2048 MB. The precise limit depends on various factors, such as how large your documents are, how many fields have norms, etc., so it's best to set this value comfortably under 2048.

        The default value is DEFAULT_RAM_BUFFER_SIZE_MB.

        Throws:
        IllegalArgumentException - if ramBufferSize is enabled but non-positive, or it disables ramBufferSize when maxBufferedDocs is already disabled
      • setMaxBufferedDeleteTerms

        @Deprecated
        public void setMaxBufferedDeleteTerms​(int maxBufferedDeleteTerms)

        Determines the minimal number of delete terms required before the buffered in-memory delete terms are applied and flushed. If there are documents buffered in memory at the time, they are merged and a new segment is created.

        Disabled by default (writer flushes by RAM usage).

        Throws:
        IllegalArgumentException - if maxBufferedDeleteTerms is enabled but smaller than 1
        See Also:
        setRAMBufferSizeMB(double)
      • setMergeFactor

        @Deprecated
        public void setMergeFactor​(int mergeFactor)
        Deprecated.
        Determines how often segment indices are merged by addDocument(). With smaller values, less RAM is used while indexing, and searches on unoptimized indices are faster, but indexing speed is slower. With larger values, more RAM is used during indexing, and while searches on unoptimized indices are slower, indexing is faster. Thus larger values (> 10) are best for batch index creation, and smaller values (< 10) for indices that are interactively maintained.

        Note that this method is a convenience method: it just calls mergePolicy.setMergeFactor as long as mergePolicy is an instance of LogMergePolicy. Otherwise an IllegalArgumentException is thrown.

        This must never be less than 2. The default value is 10.

      • getMergeFactor

        @Deprecated
        public int getMergeFactor()
        Deprecated.

        Returns the number of segments that are merged at once and also controls the total number of segments allowed to accumulate in the index.

        Note that this method is a convenience method: it just calls mergePolicy.getMergeFactor as long as mergePolicy is an instance of LogMergePolicy. Otherwise an IllegalArgumentException is thrown.

        See Also:
        setMergeFactor(int)
      • setDefaultInfoStream

        public static void setDefaultInfoStream​(PrintStream infoStream)
        If non-null, this will be the default infoStream used by a newly instantiated IndexWriter.
        See Also:
        setInfoStream(java.io.PrintStream)
      • setInfoStream

        public void setInfoStream​(PrintStream infoStream)
                           throws IOException
        If non-null, information about merges, deletes and a message when maxFieldLength is reached will be printed to this.
        Throws:
        IOException
      • verbose

        public boolean verbose()
        Returns true if verbosing is enabled (i.e., infoStream != null).
      • close

        public void close()
                   throws CorruptIndexException,
                          IOException
        Commits all changes to an index and closes all associated files. 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.

        If an Exception is hit during close, eg due to disk full or some other reason, then both the on-disk index and the internal state of the IndexWriter instance will be consistent. However, the close will not be complete even though part of it (flushing buffered documents) may have succeeded, so the write lock will still be held.

        If you can correct the underlying cause (eg free up some disk space) then you can call close() again. Failing that, if you want to force the write lock to be released (dangerous, because you may then lose buffered docs in the IndexWriter instance) then you can do something like this:

         try {
           writer.close();
         } finally {
           if (IndexWriter.isLocked(directory)) {
             IndexWriter.unlock(directory);
           }
         }
         
        after which, you must be certain not to use the writer instance anymore.

        NOTE: if this method hits an OutOfMemoryError you should immediately close the writer, again. See above for details.

        Specified by:
        close in interface AutoCloseable
        Specified by:
        close in interface Closeable
        Throws:
        CorruptIndexException - if the index is corrupt
        IOException - if there is a low-level IO error
      • close

        public void close​(boolean waitForMerges)
                   throws CorruptIndexException,
                          IOException
        Closes the index with or without waiting for currently running merges to finish. This is only meaningful when using a MergeScheduler that runs merges in background threads.

        NOTE: if this method hits an OutOfMemoryError you should immediately close the writer, again. See above for details.

        NOTE: it is dangerous to always call close(false), especially when IndexWriter is not open for very long, because this can result in "merge starvation" whereby long merges will never have a chance to finish. This will cause too many segments in your index over time.

        Parameters:
        waitForMerges - if true, this call will block until all merges complete; else, it will ask all running merges to abort, wait until those merges have finished (which should be at most a few seconds), and then return.
        Throws:
        CorruptIndexException
        IOException
      • getDirectory

        public Directory getDirectory()
        Returns the Directory used by this index.
      • getAnalyzer

        public Analyzer getAnalyzer()
        Returns the analyzer used by this index.
      • maxDoc

        public int maxDoc()
        Returns total number of docs in this index, including docs not yet flushed (still in the RAM buffer), not counting deletions.
        See Also:
        numDocs()
      • numDocs

        public int numDocs()
                    throws IOException
        Returns total number of docs in this index, including docs not yet flushed (still in the RAM buffer), and including deletions. NOTE: buffered deletions are not counted. If you really need these to be counted you should call commit() first.
        Throws:
        IOException
        See Also:
        numDocs()
      • addDocument

        public void addDocument​(Document doc)
                         throws CorruptIndexException,
                                IOException
        Adds a document to this index. If the document contains more than setMaxFieldLength(int) terms for a given field, the remainder are discarded.

        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 MergePolicy in 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 16383 characters, 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.

        NOTE: if this method hits an OutOfMemoryError you should immediately close the writer. See above for details.

        Throws:
        CorruptIndexException - if the index is corrupt
        IOException - if there is a low-level IO error
      • addDocuments

        public void addDocuments​(Collection<Document> docs)
                          throws CorruptIndexException,
                                 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(Document) 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!

        NOTE: if this method hits an OutOfMemoryError you should immediately close the writer. See above for details.

        Throws:
        CorruptIndexException - if the index is corrupt
        IOException - if there is a low-level IO error
        WARNING: This API is experimental and might change in incompatible ways in the next release.
      • addDocuments

        public void addDocuments​(Collection<Document> docs,
                                 Analyzer analyzer)
                          throws CorruptIndexException,
                                 IOException
        Atomically adds a block of documents, analyzed using the provided analyzer, with sequentially assigned document IDs, such that an external reader will see all or none of the documents.
        Throws:
        CorruptIndexException - if the index is corrupt
        IOException - if there is a low-level IO error
        WARNING: This API is experimental and might change in incompatible ways in the next release.
      • updateDocuments

        public void updateDocuments​(Term delTerm,
                                    Collection<Document> docs)
                             throws CorruptIndexException,
                                    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. See addDocuments(Collection).
        Throws:
        CorruptIndexException - if the index is corrupt
        IOException - if there is a low-level IO error
        WARNING: This API is experimental and might change in incompatible ways in the next release.
      • updateDocuments

        public void updateDocuments​(Term delTerm,
                                    Collection<Document> docs,
                                    Analyzer analyzer)
                             throws CorruptIndexException,
                                    IOException
        Atomically deletes documents matching the provided delTerm and adds a block of documents, analyzed using the provided analyzer, with sequentially assigned document IDs, such that an external reader will see all or none of the documents. See addDocuments(Collection).
        Throws:
        CorruptIndexException - if the index is corrupt
        IOException - if there is a low-level IO error
        WARNING: This API is experimental and might change in incompatible ways in the next release.
      • deleteDocuments

        public void deleteDocuments​(Term term)
                             throws CorruptIndexException,
                                    IOException
        Deletes the document(s) containing term.

        NOTE: if this method hits an OutOfMemoryError you should immediately close the writer. See above for details.

        Parameters:
        term - the term to identify the documents to be deleted
        Throws:
        CorruptIndexException - if the index is corrupt
        IOException - if there is a low-level IO error
      • deleteDocuments

        public void deleteDocuments​(Term... terms)
                             throws CorruptIndexException,
                                    IOException
        Deletes the document(s) containing any of the terms. All deletes are flushed at the same time.

        NOTE: if this method hits an OutOfMemoryError you should immediately close the writer. See above for details.

        Parameters:
        terms - array of terms to identify the documents to be deleted
        Throws:
        CorruptIndexException - if the index is corrupt
        IOException - if there is a low-level IO error
      • deleteDocuments

        public void deleteDocuments​(Query query)
                             throws CorruptIndexException,
                                    IOException
        Deletes the document(s) matching the provided query.

        NOTE: if this method hits an OutOfMemoryError you should immediately close the writer. See above for details.

        Parameters:
        query - the query to identify the documents to be deleted
        Throws:
        CorruptIndexException - if the index is corrupt
        IOException - if there is a low-level IO error
      • deleteDocuments

        public void deleteDocuments​(Query... queries)
                             throws CorruptIndexException,
                                    IOException
        Deletes the document(s) matching any of the provided queries. All deletes are flushed at the same time.

        NOTE: if this method hits an OutOfMemoryError you should immediately close the writer. See above for details.

        Parameters:
        queries - array of queries to identify the documents to be deleted
        Throws:
        CorruptIndexException - if the index is corrupt
        IOException - if there is a low-level IO error
      • updateDocument

        public void updateDocument​(Term term,
                                   Document doc)
                            throws CorruptIndexException,
                                   IOException
        Updates a document by first deleting the document(s) containing term and 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).

        NOTE: if this method hits an OutOfMemoryError you should immediately close the writer. See above for details.

        Parameters:
        term - the term to identify the document(s) to be deleted
        doc - the document to be added
        Throws:
        CorruptIndexException - if the index is corrupt
        IOException - if there is a low-level IO error
      • updateDocument

        public void updateDocument​(Term term,
                                   Document doc,
                                   Analyzer analyzer)
                            throws CorruptIndexException,
                                   IOException
        Updates a document by first deleting the document(s) containing term and 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).

        NOTE: if this method hits an OutOfMemoryError you should immediately close the writer. See above for details.

        Parameters:
        term - the term to identify the document(s) to be deleted
        doc - the document to be added
        analyzer - the analyzer to use when analyzing the document
        Throws:
        CorruptIndexException - if the index is corrupt
        IOException - if there is a low-level IO error
      • optimize

        @Deprecated
        public void optimize​(int maxNumSegments)
                      throws CorruptIndexException,
                             IOException
        Deprecated.
        This method has been deprecated, as it is horribly inefficient and very rarely justified. Lucene's multi-segment search performance has improved over time, and the default TieredMergePolicy now targets segments with deletions.
        Throws:
        CorruptIndexException
        IOException
      • optimize

        @Deprecated
        public void optimize​(boolean doWait)
                      throws CorruptIndexException,
                             IOException
        Deprecated.
        This method has been deprecated, as it is horribly inefficient and very rarely justified. Lucene's multi-segment search performance has improved over time, and the default TieredMergePolicy now targets segments with deletions.
        Throws:
        CorruptIndexException
        IOException
      • forceMerge

        public void forceMerge​(int maxNumSegments)
                        throws CorruptIndexException,
                               IOException
        Forces merge policy to merge segments until there's <= maxNumSegments. The actual merges to be executed are determined by the MergePolicy.

        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 up to 2X the index size free space in your Directory (3X if you're using compound file format). For example, if your index size is 10 MB then you need up to 20 MB free for this to complete (30 MB if you're using compound file format). Also, it's best to call commit() afterwards, to allow IndexWriter to free up disk space.

        If some but not all readers re-open while merging is underway, this will cause > 2X temporary 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 the 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 corrupt and no documents will have been 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.

        NOTE: if this method hits an OutOfMemoryError you should immediately close the writer. See above for details.

        NOTE: if you call close(boolean) with false, which aborts all running merges, then any thread still running this method might hit a MergePolicy.MergeAbortedException.

        Parameters:
        maxNumSegments - maximum number of segments left in the index after merging finishes
        Throws:
        CorruptIndexException - if the index is corrupt
        IOException - if there is a low-level IO error
        See Also:
        MergePolicy.findMerges(org.apache.lucene.index.SegmentInfos)
      • expungeDeletes

        @Deprecated
        public void expungeDeletes​(boolean doWait)
                            throws CorruptIndexException,
                                   IOException
        Deprecated.
        This method has been deprecated, as it is horribly inefficient and very rarely justified. Lucene's multi-segment search performance has improved over time, and the default TieredMergePolicy now targets segments with deletions.
        Throws:
        CorruptIndexException
        IOException
      • expungeDeletes

        @Deprecated
        public void expungeDeletes()
                            throws CorruptIndexException,
                                   IOException
        Deprecated.
        This method has been deprecated, as it is horribly inefficient and very rarely justified. Lucene's multi-segment search performance has improved over time, and the default TieredMergePolicy now targets segments with deletions.
        Throws:
        CorruptIndexException
        IOException
      • forceMergeDeletes

        public void forceMergeDeletes()
                               throws CorruptIndexException,
                                      IOException
        Forces merging of all segments that have deleted documents. The actual merges to be executed are determined by the MergePolicy. For example, the default TieredMergePolicy will 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.

        NOTE: if this method hits an OutOfMemoryError you should immediately close the writer. See above for details.

        Throws:
        CorruptIndexException
        IOException
      • maybeMerge

        public final void maybeMerge()
                              throws CorruptIndexException,
                                     IOException
        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.

        NOTE: if this method hits an OutOfMemoryError you should immediately close the writer. See above for details.

        Throws:
        CorruptIndexException
        IOException
      • getMergingSegments

        public Collection<SegmentInfo> getMergingSegments()
        Expert: to be used by a MergePolicy to 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).

        Do not alter the returned collection!

      • getNextMerge

        public MergePolicy.OneMerge getNextMerge()
        Expert: the MergeScheduler calls this method to retrieve the next merge requested by the MergePolicy
        WARNING: This API is experimental and might change in incompatible ways in the next release.
      • rollback

        public void rollback()
                      throws IOException
        Close the IndexWriter without 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 to prepareCommit().
        Specified by:
        rollback in interface TwoPhaseCommit
        Throws:
        IOException - if there is a low-level IO error
      • waitForMerges

        public void waitForMerges()
        Wait for any currently outstanding merges to finish.

        It is guaranteed that any merges started prior to calling this method will have completed once this method completes.

      • addIndexes

        public void addIndexes​(Directory... dirs)
                        throws CorruptIndexException,
                               IOException
        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: the index in each Directory must not be changed (opened by a writer) while this method is running. This method does not acquire a write lock in each input Directory, so it is up to the caller to enforce this.

        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 Directory up 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 (see forceMerge(int) for details).

        NOTE: this method only copies the segments of the incomning indexes and does not merge them. Therefore deleted documents are not removed and the new segments are not merged with the existing ones.

        This requires this index not be among those to be added.

        NOTE: if this method hits an OutOfMemoryError you should immediately close the writer. See above for details.

        Throws:
        CorruptIndexException - if the index is corrupt
        IOException - if there is a low-level IO error
      • addIndexes

        public void addIndexes​(IndexReader... readers)
                        throws CorruptIndexException,
                               IOException
        Merges the provided indexes into this index. This method is useful if you use extensions of IndexReader. Otherwise, using addIndexes(Directory...) is highly recommended for performance reasons. It uses the MergeScheduler and MergePolicy set on this writer, which may perform merges in parallel.

        The provided IndexReaders are not closed.

        NOTE: this method does not merge the current segments, only the incoming ones.

        See addIndexes(Directory...) for details on transactional semantics, temporary free space required in the Directory, and non-CFS segments on an Exception.

        NOTE: if this method hits an OutOfMemoryError you should immediately close the writer. See above for details.

        NOTE: if you call close(boolean) with false, which aborts all running merges, then any thread still running this method might hit a MergePolicy.MergeAbortedException.

        Throws:
        CorruptIndexException - if the index is corrupt
        IOException - if there is a low-level IO error
      • doAfterFlush

        protected void doAfterFlush()
                             throws IOException
        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
      • doBeforeFlush

        protected void doBeforeFlush()
                              throws IOException
        A hook for extending classes to execute operations before pending added and deleted documents are flushed to the Directory.
        Throws:
        IOException
      • prepareCommit

        public final void prepareCommit​(Map<String,​String> commitUserData)
                                 throws CorruptIndexException,
                                        IOException

        Expert: prepare for commit, specifying commitUserData Map (String -> String). 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 either commit() to finish the commit, or rollback() to revert the commit and undo all changes done since the writer was opened.

        You can also just call commit(Map) directly without prepareCommit first in which case that method will internally call prepareCommit.

        NOTE: if this method hits an OutOfMemoryError you should immediately close the writer. See above for details.

        Specified by:
        prepareCommit in interface TwoPhaseCommit
        Parameters:
        commitUserData - Opaque Map (String->String) that's recorded into the segments file in the index, and retrievable by IndexCommit.getUserData(). Note that when IndexWriter commits itself during close(), the commitUserData is unchanged (just carried over from the prior commit). If this is null then the previous commitUserData is kept. Also, the commitUserData will only "stick" if there are actually changes in the index to commit.
        Throws:
        CorruptIndexException
        IOException
        See Also:
        TwoPhaseCommit.prepareCommit()
      • commit

        public final void commit()
                          throws CorruptIndexException,
                                 IOException

        Commits all pending changes (added & 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 & 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.

        NOTE: if this method hits an OutOfMemoryError you should immediately close the writer. See above for details.

        Specified by:
        commit in interface TwoPhaseCommit
        Throws:
        CorruptIndexException
        IOException
        See Also:
        prepareCommit(), commit(Map)
      • flush

        protected final void flush​(boolean triggerMerge,
                                   boolean applyAllDeletes)
                            throws CorruptIndexException,
                                   IOException
        Flush all in-memory buffered updates (adds and deletes) to the Directory.
        Parameters:
        triggerMerge - if true, we may merge segments (if deletes or docs were flushed) if necessary
        applyAllDeletes - whether pending deletes should also
        Throws:
        CorruptIndexException
        IOException
      • ramSizeInBytes

        public final long ramSizeInBytes()
        Expert: Return the total size of all index files currently cached in memory. Useful for size management with flushRamDocs()
      • numRamDocs

        public final int numRamDocs()
        Expert: Return the number of documents currently buffered in RAM.
      • segString

        public String segString()
                         throws IOException
        Throws:
        IOException
        NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.
      • segString

        public String segString​(SegmentInfo info)
                         throws IOException
        Throws:
        IOException
        NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.
      • isLocked

        public static boolean isLocked​(Directory directory)
                                throws IOException
        Returns true iff the index in the named directory is currently locked.
        Parameters:
        directory - the directory to check for a lock
        Throws:
        IOException - if there is a low-level IO error
      • unlock

        public static void unlock​(Directory directory)
                           throws IOException
        Forcibly unlocks the index in the named directory.

        Caution: this should only be used by failure recovery code, when it is known that no other process nor thread is in fact currently accessing this index.

        Throws:
        IOException
      • deleteUnusedFiles

        public void deleteUnusedFiles()
                               throws IOException
        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 IndexDeletionPolicy which 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