Class IndexWriter

Constructs a new IndexWriter per the settings given in conf. If you want to make "live" changes to this writer instance, use Config.

NOTE: after ths writer is created, the given configuration instance cannot be passed to another writer. If you intend to do so, you should Clone() it beforehand.

Absolute hard maximum length for a term, in bytes once encoded as UTF8. If a term arrives from the analyzer longer than this length, an is thrown and a message is printed to Lucene.Net.Index.IndexWriter.infoStream, if set (see SetInfoStream(InfoStream)).

Key for the source of a segment in the Diagnostics.

Source of a segment which results from a call to AddIndexes(IndexReader[]).

Source of a segment which results from a flush.

Source of a segment which results from a merge of other segments.

Name of the write lock in the index.

Set to false to return an overall failure if the request would produce partial results. Set to true, which will allow partial results in the case of partial cluster.

Gets the analyzer used by this index.

Returns the commit user data map that was last committed, or the one that was set on SetCommitData(IDictionary<String, String>).

Returns a LiveIndexWriterConfig, which can be used to query the IndexWriter current settings, as well as modify "live" ones.

Gets the Directory used by this index.

Only for testing.

@lucene.internal

Gets total number of docs in this index, including docs not yet flushed (still in the RAM buffer), not counting deletions.

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!

Gets 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.

Index writer operations are all Async. Returns true if all are complete.

Adds a document to this index.

Note that if an 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 IndexWriter), 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(Int32) 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_LENGTH in bytes, otherwise an 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 you should immediately dispose the writer. See IndexWriter for details.

Adds a document to this index, using the provided analyzer instead of the value of Analyzer.

See AddDocument(IEnumerable<IIndexableField>) for details on index and IndexWriter state after an , and flushing/merging temporary free space requirements.

NOTE: if this method hits an you should immediately dispose the writer. See IndexWriter for details.

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(IEnumerable<IIndexableField>) for details on index and IndexWriter state after an , and flushing/merging temporary free space requirements.

NOTE: tools that do offline splitting of an index (for example, IndexSplitter in Lucene.Net.Misc) 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 you should immediately dispose the writer. See IndexWriter for details.

@lucene.experimental

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.

@lucene.experimental

Merges the provided indexes into this index.

The provided IndexReaders are not closed.

See AddIndexes(IndexReader[]) for details on transactional semantics, temporary free space required in the Directory, and non-CFS segments on an .

NOTE: if this method hits an you should immediately dispose the writer. See IndexWriter for details.

NOTE: empty segments are dropped by this method and not added to this index.

NOTE: this method merges all given IndexReaders in one merge. If you intend to merge a large number of readers, it may be better to call this method multiple times, each time with a small set of readers. In principle, if you use a merge policy with a mergeFactor or maxMergeAtOnce parameter, you should pass that many readers in one call. Also, if the given readers are DirectoryReaders, they can be opened with termIndexInterval=-1 to save RAM, since during merge the in-memory structure is not used. See Open(Directory, Int32).

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

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 IndexWriter is currently open or tries to open while this is running.

This method is transactional in how s are handled: it does not commit a new segments_N file until all indexes are added. this means if an 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(Int32) for details).

NOTE: this method only copies the segments of the incoming 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 you should immediately dispose the writer. See IndexWriter for details.

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 Sync(ICollection<String>) 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 you should immediately dispose the writer. See IndexWriter for details.

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 using Rollback().

NOTE: this method is much faster than using DeleteDocuments(new MatchAllDocsQuery()). Yet, this method also has different semantics compared to DeleteDocuments(Query) / 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 to DeleteAll() is equivalent to creating a new IndexWriter with CREATE which a delete query only marks documents as deleted.

NOTE: this method will forcefully abort all merges in progress. If other threads are running ForceMerge(Int32), AddIndexes(IndexReader[]) or ForceMergeDeletes() methods, they may receive MergePolicy.MergeAbortedExceptions.

Deletes the document(s) containing term.

NOTE: if this method hits an you should immediately dispose the writer. See IndexWriter for details.

Deletes the document(s) containing any of the terms. All given deletes are applied and flushed atomically at the same time.

NOTE: if this method hits an you should immediately dispose the writer. See IndexWriter for details.

Deletes the document(s) matching the provided query.

NOTE: if this method hits an you should immediately dispose the writer. See IndexWriter for details.

Deletes the document(s) matching any of the provided queries. All given deletes are applied and flushed atomically at the same time.

NOTE: if this method hits an you should immediately dispose the writer. See IndexWriter for details.

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.

Commits all changes to an index, waits for pending merges to complete, and closes all associated files.

This is a "slow graceful shutdown" which may take a long time especially if a big merge is pending: If you only want to close resources use Rollback(). If you only want to commit pending changes and close resources see Dispose(Boolean).

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 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 Dispose() 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.Dispose();
} 
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 you should immediately dispose the writer, again. See IndexWriter for details.

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 you should immediately dispose the writer, again. See IndexWriter for details.

NOTE: it is dangerous to always call Dispose(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.

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).

A hook for extending classes to execute operations before pending added and deleted documents are flushed to the Directory.

Used internally to throw an if this IndexWriter has been disposed (closed=true) or is in the process of disposing (closing=true).

Calls EnsureOpen(Boolean).

Used internally to throw an if this IndexWriter has been disposed or is in the process of diposing.

Flush all in-memory buffered updates (adds and deletes) to the Directory.

Forces merge policy to merge segments until there are <= 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 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 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 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(Int32) again.

NOTE: if this method hits an you should immediately dispose the writer. See IndexWriter for details.

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

Just like ForceMerge(Int32), except you can specify whether the call should block until all merging completes. This is only meaningful with a Lucene.Net.Index.IndexWriter.mergeScheduler that is able to run merges in background threads.

NOTE: if this method hits an you should immediately dispose the writer. See IndexWriter for details.

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 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 you should immediately dispose the writer. See IndexWriter for details.

Just like ForceMergeDeletes(), except you can specify whether the call should block until the operation completes. This is only meaningful with a MergeScheduler that is able to run merges in background threads.

NOTE: if this method hits an you should immediately dispose the writer. See IndexWriter for details.

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

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 opening a new reader. But the turnaround 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 DoOpenIfChanged(), 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 set MergedSegmentWarmer 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 disposed, any outstanding readers may continue to be used. However, if you attempt to reopen any of those readers, you'll hit an .

@lucene.experimental

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. Also, if a merge kicked off as a result of flushing a

Expert: returns true if there are merges waiting to be scheduled.

@lucene.experimental

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 during Commit(), or a concurrent merged finished, this method may return true right after you had just called Commit().

Returns true iff the index in the named directory is currently locked.

Expert: asks the Lucene.Net.Index.IndexWriter.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 Lucene.Net.Index.IndexWriter.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 Lucene.Net.Index.IndexWriter.mergePolicy with EXPLICIT.

NOTE: if this method hits an you should immediately dispose the writer. See IndexWriter for details.

Merges the indicated segments, replacing them in the stack with a single segment.

@lucene.experimental

Does fininishing for a merge, which is fast but holds the synchronized lock on IndexWriter instance.

Expert: the Lucene.Net.Index.IndexWriter.mergeScheduler calls this method to retrieve the next merge requested by the MergePolicy

@lucene.experimental

Obtain the number of deleted docs for a pooled reader. If the reader isn't being pooled, the segmentInfo's delCount is returned.

Expert: Return the number of documents currently buffered in RAM.

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 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() directly without PrepareCommit() first in which case that method will internally call PrepareCommit().

NOTE: if this method hits an you should immediately dispose the writer. See IndexWriter for details.

Expert: Return the total size of all index files currently cached in memory. Useful for size management with flushRamDocs()

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().

Returns a string description of all segments, for debugging.

@lucene.internal

Returns a string description of the specified segments, for debugging.

@lucene.internal

Returns a string description of the specified segment, for debugging.

@lucene.internal

Sets the commit user data map. That method is considered a transaction by IndexWriter and will be committed (Commit() even if no other changes were made to the writer instance. Note that you must call this method before PrepareCommit(), or otherwise it won't be included in the follow-on Commit().

NOTE: the dictionary is cloned internally, therefore altering the dictionary's contents after calling this method has no effect.

Expert: attempts to delete by document ID, as long as the provided readerIn is a near-real-time reader (from Open(IndexWriter, Boolean). If the provided readerIn is an NRT reader obtained from this writer, and its segment has not been merged away, then the delete succeeds and this method returns true; else, it returns false 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 the other DeleteDocument() methods (e.g., DeleteDocuments(Term)).

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.

Updates a document's BinaryDocValues for field to the given value. this method can be used to 'unset' a document's value by passing null as the new value. Also, you can only update fields that already exist in the index, not add new fields through this method.

NOTE: this method currently replaces the existing value of all affected documents with the new value.

NOTE: if this method hits an you should immediately dispose the writer. See IndexWriter for details.

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 you should immediately dispose the writer. See IndexWriter for details.

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 you should immediately dispose the writer. See IndexWriter for details.

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.

@lucene.experimental

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.

@lucene.experimental

Updates a document's NumericDocValues for field to the given value. This method can be used to 'unset' a document's value by passing null as the new value. Also, you can only update fields that already exist in the index, not add new fields through this method.

NOTE: if this method hits an you should immediately dispose the writer. See IndexWriter for details.

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.