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https://issues.apache.org/jira/browse/LUCENE-1516?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12675490#action_12675490
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Michael McCandless commented on LUCENE-1516:
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bq. It's hard keeping up with the current proposal in big issues/threads, but I
don't think anyone is proposing a reader that automatically sees changes...
i.e. the view of an IndexReader instance will still be fixed.
That's right. The current proposal is to add one method to IW:
{code}
IndexReader getReader()
{code}
that returns a point-in-time view of the index plus all changes
buffered in IW up until that point. Then you can reopen that reader
(or call getReader() again, which does the same thing) to quickly get
a new point-in-time reader.
I think the point-in-time semantics is important to keep.
Also, you can't easily emulate point-in-time if we implemented the
"live" approach, but you can easily do vice/versa (assuming we can
keep reopen() time fast enough).
EG the IndexAccessor convenience layer could do automatic reopening so
that when you ask it for the reader it always reopens it; this would
emulate "live updates" and hide the lifecycle management.
> Integrate IndexReader with IndexWriter
> ---------------------------------------
>
> Key: LUCENE-1516
> URL: https://issues.apache.org/jira/browse/LUCENE-1516
> Project: Lucene - Java
> Issue Type: Improvement
> Affects Versions: 2.4
> Reporter: Jason Rutherglen
> Assignee: Michael McCandless
> Priority: Minor
> Fix For: 2.9
>
> Attachments: LUCENE-1516.patch, LUCENE-1516.patch, LUCENE-1516.patch,
> LUCENE-1516.patch, LUCENE-1516.patch, LUCENE-1516.patch, LUCENE-1516.patch
>
> Original Estimate: 672h
> Remaining Estimate: 672h
>
> The current problem is an IndexReader and IndexWriter cannot be open
> at the same time and perform updates as they both require a write
> lock to the index. While methods such as IW.deleteDocuments enables
> deleting from IW, methods such as IR.deleteDocument(int doc) and
> norms updating are not available from IW. This limits the
> capabilities of performing updates to the index dynamically or in
> realtime without closing the IW and opening an IR, deleting or
> updating norms, flushing, then opening the IW again, a process which
> can be detrimental to realtime updates.
> This patch will expose an IndexWriter.getReader method that returns
> the currently flushed state of the index as a class that implements
> IndexReader. The new IR implementation will differ from existing IR
> implementations such as MultiSegmentReader in that flushing will
> synchronize updates with IW in part by sharing the write lock. All
> methods of IR will be usable including reopen and clone.
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