public abstract class IndexDeletionPolicy extends Object
Expert: policy for deletion of stale
Implement this interface, and pass it to one
constructors, to customize when older
are deleted from the index directory. The default deletion policy
KeepOnlyLastCommitDeletionPolicy, which always
removes old commits as soon as a new commit is done (this
matches the behavior before 2.2).
One expected use case for this (and the reason why it
was first created) is to work around problems with an
index directory accessed via filesystems like NFS because
NFS does not provide the "delete on last close" semantics
that Lucene's "point in time" search normally relies on.
By implementing a custom deletion policy, such as "a
commit is only removed once it has been stale for more
than X minutes", you can give your readers time to
refresh to the new commit before
removes the old commits. Note that doing so will
increase the storage requirements of the index. See LUCENE-710
|Modifier||Constructor and Description|
Sole constructor, typically called by sub-classes constructors.
|Modifier and Type||Method and Description|
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.
public abstract void onInit(List<? extends IndexCommit> commits) throws IOException
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
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.
public abstract void onCommit(List<? extends IndexCommit> commits) throws IOException
This is called each time the writer completed a commit. This gives the policy a chance to remove old commit points with each commit.
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