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From "Jason Rutherglen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1516) Integrate IndexReader with IndexWriter
Date Tue, 30 Jun 2009 20:10:48 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1516?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12725779#action_12725779
] 

Jason Rutherglen commented on LUCENE-1516:
------------------------------------------

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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