| java.lang.Object | |
| ↳ | org.apache.lucene.index.SnapshotDeletionPolicy |
Class Overview
A IndexDeletionPolicy that wraps around any other
IndexDeletionPolicy and adds the ability to hold and
later release a single "snapshot" of an index. While
the snapshot is held, the IndexWriter will not
remove any files associated with it even if the index is
otherwise being actively, arbitrarily changed. Because
we wrap another arbitrary IndexDeletionPolicy, this
gives you the freedom to continue using whatever IndexDeletionPolicy you would normally want to use with your
index. Note that you can re-use a single instance of
SnapshotDeletionPolicy across multiple writers as long
as they are against the same index Directory. Any
snapshot held when a writer is closed will "survive"
when the next writer is opened.
WARNING: This API is a new and experimental and may suddenly change.
Summary
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| Public Methods | |||||||||||
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This is called each time the writer completed a commit. | |||||||||||
This is called once when a writer is first instantiated to give the policy a chance to remove old commit points. | |||||||||||
Release the currently held snapshot.
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Take a snapshot of the most recent commit to the
index.
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[Expand]
Inherited Methods | |||||||||||
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From class
java.lang.Object
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From interface
org.apache.lucene.index.IndexDeletionPolicy
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Public Constructors
Public Methods
public synchronized void onCommit (List<? extends IndexCommit> commits)
This is called each time the writer completed a commit. This gives the policy a chance to remove old commit points with each commit.
The policy may now choose to delete old commit points
by calling method delete()
of IndexCommit.
This method is only called when commit() or close() is
called, or possibly not at all if the rollback() is called.
Note: the last CommitPoint is the most recent one, i.e. the "front index state". Be careful not to delete it, unless you know for sure what you are doing, and unless you can afford to lose the index content while doing that.
Parameters
| commits | List of IndexCommit,
sorted by age (the 0th one is the oldest commit).
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Throws
| IOException |
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public synchronized void onInit (List<? extends IndexCommit> commits)
This is called once when a writer is first instantiated to give the policy a chance to remove old commit points.
The writer locates all index commits present in the
index directory and calls this method. The policy may
choose to delete some of the commit points, doing so by
calling method delete()
of IndexCommit.
Note: the last CommitPoint is the most recent one, i.e. the "front index state". Be careful not to delete it, unless you know for sure what you are doing, and unless you can afford to lose the index content while doing that.
Parameters
| commits | List of current
point-in-time commits,
sorted by age (the 0th one is the oldest commit).
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Throws
| IOException |
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public synchronized void release ()
Release the currently held snapshot.
public synchronized IndexCommit snapshot ()
Take a snapshot of the most recent commit to the index. You must call release() to free this snapshot. Note that while the snapshot is held, the files it references will not be deleted, which will consume additional disk space in your index. If you take a snapshot at a particularly bad time (say just before you call optimize()) then in the worst case this could consume an extra 1X of your total index size, until you release the snapshot.