[LUCENE-1411] Enable IndexWriter to open an arbitrary commit point

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 2.4
• Fix Version/s: 2.9
• Component/s: core/index
• Lucene Fields: New
• Assignee: Michael McCandless
• Reporter: Michael McCandless
• Created: 02/Oct/08 11:39
• Updated: 28/Aug/22 11:53
• Resolved: 20/Oct/08 09:49

Description

With a 2-phase commit involving multiple resources, each resource
first does its prepareCommit and then if all are successful they each
commit. If an exception or timeout/power loss is hit in any of the
resources during prepareCommit or commit, all of the resources must
then rollback.

But, because IndexWriter always opens the most recent commit, getting
Lucene to rollback after commit() has been called is not easy, unless
you make Lucene the last resource to commit. A simple workaround is
to simply remove the segments_N files of the newer commits but that's
sort of a hassle.

To fix this, we just need to add a ctor to IndexWriter that takes an
IndexCommit. We recently added this for IndexReader (LUCENE-1311) as
well. This ctor is definitely an "expert" method, and only makes
sense if you have a custom DeletionPolicy that preserves more than
just the most recent commit.