Class IndexFileDeleter
This class keeps track of each SegmentInfos instance that is still "live", either because it corresponds to a segments_N file in the Directory (a "commit", i.e. a committed SegmentInfos) or because it's an in-memory SegmentInfos that a writer is actively updating but has not yet committed. This class uses simple reference counting to map the live SegmentInfos instances to individual files in the Directory.
The same directory file may be referenced by more than one IndexCommit, i.e. more than one SegmentInfos. Therefore we count how many commits reference each file. When all the commits referencing a certain file have been deleted, the refcount for that file becomes zero, and the file is deleted.
A separate deletion policy interface (IndexDeletionPolicy) is consulted on creation (onInit) and once per commit (onCommit), to decide when a commit should be removed.
It is the business of the IndexDeletionPolicy to choose when to delete commit points. The actual mechanics of file deletion, retrying, etc, derived from the deletion of commit points is the business of the IndexFileDeleter.
The current default deletion policy is KeepOnlyLastCommitDeletionPolicy, which removes all prior commits when a new commit has completed. This matches the behavior before 2.2.
Note that you must hold the write.lock before instantiating this class. It opens segments_N file(s) directly with no retry logic.
Inheritance
Namespace:
Assembly: Lucene.Net.NetCore.dll
Syntax
public sealed class IndexFileDeleter : IDisposableConstructors
| Name | Description |
|---|---|
| IndexFileDeleter(Directory, IndexDeletionPolicy, SegmentInfos, IO.StreamWriter, DocumentsWriter, HashSet<String>) | Initialize the deleter: find all previous commits in the Directory, incref the files they reference, call the policy to let it delete commits. This will remove any files not referenced by any of the commits. |
Fields
| Name | Description |
|---|---|
| VERBOSE_REF_COUNTS | Change to true to see details of reference counts when infoStream != null |
Properties
| Name | Description |
|---|---|
| LastSegmentInfos |
Methods
| Name | Description |
|---|---|
| Checkpoint(SegmentInfos, Boolean) | For definition of "check point" see IndexWriter comments: "Clarification: Check Points (and commits)". Writer calls this when it has made a "consistent change" to the index, meaning new files are written to the index and the in-memory SegmentInfos have been modified to point to those files. This may or may not be a commit (segments_N may or may not have been written). We simply incref the files referenced by the new SegmentInfos and decref the files we had previously seen (if any). If this is a commit, we also call the policy to give it a chance to remove other commits. If any commits are removed, we decref their files as well. |
| Dispose() | |
| Exists(String) | |
| Refresh() | |
| Refresh(String) | Writer calls this when it has hit an error and had to roll back, to tell us that there may now be unreferenced files in the filesystem. So we re-list the filesystem and delete such files. If segmentName is non-null, we will only delete files corresponding to that segment. |