[LUCENE-1651] Make IndexReader.open() always return MSR to simplify (re-)opens.

• Type: Task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.9
• Fix Version/s: 2.9
• Lucene Fields: New
• Assignee: Michael McCandless
• Reporter: Earwin Burrfoot
• Created: 21/May/09 15:46
• Updated: 28/Aug/22 12:01
• Resolved: 07/Jun/09 16:34

Description

As per discussion in mailing list, I'm making DirectoryIndexReader.open() always return MSR, even for single-segment indexes.
While theoretically valid in the past (if you make sure to keep your index constantly optimized) this feature is made practically obsolete by per-segment collection.

The patch somewhat de-hairies (re-)open logic for MSR/SR.
SR no longer needs an ability to pose as toplevel directory-owning IR.
All related logic is moved from DIR to MSR.
DIR becomes almost empty, and copying two or three remaining fields over to MSR/SR, I remove it.
Lots of tests fail, as they rely on SR returned from IR.open(), I fix by introducing SR.getOnlySegmentReader static package-private method.
Some previous bugs are uncovered, one is fixed in LUCENE-1645, another (partially fixed in LUCENE-1648) is fixed in this patch.

Issue Links

• is depended upon by: LUCENE-1648 when you clone or reopen an IndexReader with pending changes, the new reader doesn't commit the changes