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https://issues.apache.org/jira/browse/LUCENE-1516?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12725779#action_12725779
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Jason Rutherglen commented on LUCENE-1516:
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I think we will want to do something like what field cache does
with CreationPlaceholder for IndexWriter.readerPool. Otherwise
we have the (I think somewhat problematic) issue of all other
readerPool.get* methods waiting for an SR to warm.
{code}
public synchronized SegmentReader get(SegmentInfo info, boolean doOpenStores,
int readBufferSize) throws IOException {
if (poolReaders) {
readBufferSize = BufferedIndexInput.BUFFER_SIZE;
}
SegmentReader sr = (SegmentReader) readerMap.get(info);
if (sr == null) {
// TODO: we may want to avoid doing this while
// synchronized
// Returns a ref, which we xfer to readerMap:
sr = SegmentReader.get(info, readBufferSize, doOpenStores);
readerMap.put(info, sr);
} else if (doOpenStores) {
sr.openDocStores();
}
// Return a ref to our caller
sr.incRef();
return sr;
}
{code}
> 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,
> LUCENE-1516.patch, LUCENE-1516.patch, LUCENE-1516.patch, LUCENE-1516.patch,
> LUCENE-1516.patch, LUCENE-1516.patch, LUCENE-1516.patch, LUCENE-1516.patch,
> LUCENE-1516.patch, LUCENE-1516.patch, LUCENE-1516.patch, LUCENE-1516.patch,
> LUCENE-1516.patch, LUCENE-1516.patch, LUCENE-1516.patch, LUCENE-1516.patch,
> LUCENE-1516.patch, LUCENE-1516.patch, LUCENE-1516.patch, LUCENE-1516.patch,
> LUCENE-1516.patch, magnetic.png, ssd.png, ssd2.png
>
> 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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