jason rutherglen wrote:
Interesting, does this mean there is a plan for incrementally updateable
IndexSearchers to become part of Lucene?
In general, there is no plan for Lucene. If someone implements a
generally useful, efficient, feature in a back-compatible, easy to use,
manner, and submits it as a patch, then it becomes a part of Lucene.
That's the way Lucene changes. Since we don't pay anyone, we can't make
plans and assign tasks. So if you're particularly interested in this
feature, you might search the archives to find past efforts, or simply
try to implement it yourself.
I think a good approach would be to create a new IndexSearcher instance
based on an existing one, that shares IndexReaders. Similarly, one
should be able to create a new IndexReader based on an existing one.
This would be a MultiReader that shares many of the same SegmentReaders.
Things get a little tricky after this.
Lucene caches filters based on the IndexReader. So filters would need
to be re-created. Ideally these could be incrementally re-created, but
that might be difficult. What might be simpler would be to use a
MultiSearcher constructed with an IndexSearcher per SegmentReader,
avoiding the use of MultiReader. Then the caches would still work.
This would require making a few things public that are not at present.
Perhaps adding a 'MultiReader.getSubReaders()' method, combined with an
'static IndexReader.reopen(IndexReader)' method. The latter would
return a new MultiReader that shared SegmentReaders with the old
version. Then one could use getSubReaders() on the new multi reader to
extract the current set to use when constructing a MultiSearcher.
Another tricky bit is figuring out when to close readers.
Does this make sense? This discussion should probably move to the
lucene-dev list.
Are there any negatives to updateable IndexSearchers?
Not if implemented well!
Doug
