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List:       lucene-user
Subject:    RE: How to properly refresh MultiReader IndexSearcher in Lucene 4.0-BETA
From:       "Uwe Schindler" <uwe () thetaphi ! de>
Date:       2012-08-28 8:09:07
Message-ID: 00e201cd84f4$6602f950$3208ebf0$ () thetaphi ! de
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Hi,

your code unfortunatley will no longer work in later Lucene 4.0 releases.

In general the simpliest and "correct" way to do this is:
- Manage your DirectoryReaders completely separate from each other in something like \
a pool of subindex readers (e.g. use some too like SearcherManager to keep the alive, \
this is much easier than doing it yourself). Once you need to reopen one, just reopen \
                it and save it.
- On *every* search create a new MultiReader() [this costs nothing, as it is just a \
wrapper] and wrap it with a new IndexSearcher [this also costs you nothing, as it is \
also just a wrapper].

Uwe

-----
Uwe Schindler
H.-H.-Meier-Allee 63, D-28213 Bremen
http://www.thetaphi.de
eMail: uwe@thetaphi.de


> -----Original Message-----
> From: Mossaab Bagdouri [mailto:bagdouri_mossaab@yahoo.fr]
> Sent: Monday, August 27, 2012 7:37 PM
> To: java-user@lucene.apache.org
> Subject: How to properly refresh MultiReader IndexSearcher in Lucene 4.0-
> BETA
> 
> Hi,
> 
> The context is that I've migrated from Lucene 3.6 to Lucene 4.0-BETA.
> Lucene 3.6 had the convenient method IndexSearcher.isCurrent() for any
> underlying IndexReader, including MultiReader. This is no more the case for
> Lucene 4.0-BETA. I've been suffering in the last 48h until I came up with this
> solution. I just want to share, and get feedbacks if any. The idea is to create a
> new instance of MultiReader, add the old current SubReaders and the new
> changed ones, refresh the IndexSearcher, then close the old out-of-date
> SubReaders.
> 
> private IndexSearcher getIndexSearcher() {
> try {
> if (is == null || is.getIndexReader().getRefCount() == 0) {
> DirectoryReader newReaders[] = new DirectoryReader[2];
> for (int i = 0; i < 2; i++) {
> newReaders[i] =
> DirectoryReader.open(MyFSDirectories.get(i));
> }
> is = new IndexSearcher(new MultiReader(newReaders));
> } else {
> MultiReader mr = (MultiReader) is.getIndexReader();
> List<DirectoryReader> oldReaders = (List<DirectoryReader>)
> mr.getSequentialSubReaders();
> DirectoryReader newReaders[] = new
> DirectoryReader[oldReaders.size()];
> Set<Integer> toClose = new HashSet<>();
> for (int i = 0; i < oldReaders.size(); i++) {
> DirectoryReader oldDirectoryReader = oldReaders.get(i);
> if (oldDirectoryReader.isCurrent()) {
> newReaders[i] = oldDirectoryReader;
> } else {
> toClose.add(i);
> newReaders[i] =
> DirectoryReader.openIfChanged(oldReaders.get(i));
> }
> }
> 
> is = new IndexSearcher(new MultiReader(newReaders));
> 
> for (int i : toClose) {
> oldReaders.get(i).close();
> }
> }
> } catch (Exception e) {
> e.printStackTrace();
> }
> return is;
> }
> 
> Regards,
> Mossaab


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