Some house cleaning in addIndexes*
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Key: LUCENE-2455
URL: https://issues.apache.org/jira/browse/LUCENE-2455
Project: Lucene - Java
Issue Type: Improvement
Components: Index
Reporter: Shai Erera
Assignee: Shai Erera
Priority: Trivial
Fix For: 3.1, 4.0
Today, the use of addIndexes and addIndexesNoOptimize is confusing -
especially on when to invoke each. Also, addIndexes calls optimize() in
the beginning, but only on the target index. It also includes the
following jdoc statement, which from how I understand the code, is
wrong: _After this completes, the index is optimized._ -- optimize() is
called in the beginning and not in the end.
On the other hand, addIndexesNoOptimize does not call optimize(), and
relies on the MergeScheduler and MergePolicy to handle the merges.
After a short discussion about that on the list (Thanks Mike for the
clarifications!) I understand that there are really two core differences
between the two:
* addIndexes supports IndexReader extensions
* addIndexesNoOptimize performs better
This issue proposes the following:
# Clear up the documentation of each, spelling out the pros/cons of
calling them clearly in the javadocs.
# Rename addIndexesNoOptimize to addIndexes
# Remove optimize() call from addIndexes(IndexReader...)
# Document that clearly in both, w/ a recommendation to call optimize()
before on any of the Directories/Indexes if it's a concern.
That way, we maintain all the flexibility in the API -
addIndexes(IndexReader...) allows for using IR extensions,
addIndexes(Directory...) is considered more efficient, by allowing the
merges to happen concurrently (depending on MS) and also factors in the
MP. So unless you have an IR extension, addDirectories is really the one
you should be using. And you have the freedom to call optimize() before
each if you care about it, or don't if you don't care. Either way,
incurring the cost of optimize() is entirely in the user's hands.
BTW, addIndexes(IndexReader...) does not use neither the MergeScheduler
nor MergePolicy, but rather call SegmentMerger directly. This might be
another place for improvement. I'll look into it, and if it's not too
complicated, I may cover it by this issue as well. If you have any hints
that can give me a good head start on that, please don't be shy :).
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