Yes, that's a good start. Your patch does not handle deletions
correctly. If a segment has had deletions since it was opened then its
deletions file needs to be re-read. I also think returning a new
IndexReader is preferable to modifying one, since an IndexReader is
often used as a cache key, and caches should be invalidated when an
IndexReader is re-opened.
Robert Engels wrote:
I proposed and posted a patch for this long ago. Only thing missing would be
some sort of reference courting for segments (rather than the 'stayopen'
flag).
/**
* reopens the IndexReader, possibly reusing the segments for greater
efficiency. The original IndexReader instance
* is closed, and the reference is no longer valid
*
* @return the new IndexReader
*/
public IndexReader reopen() throws IOException {
if(!(this instanceof MultiReader))
return IndexReader.open(directory);
MultiReader mr = (MultiReader) this;
final IndexReader[] oldreaders = mr.getReaders();
final boolean[] stayopen = new boolean[oldreaders.length];
synchronized (directory) { // in- &
inter-process sync
return (IndexReader)new Lock.With(
directory.makeLock(IndexWriter.COMMIT_LOCK_NAME),
IndexWriter.COMMIT_LOCK_TIMEOUT) {
public Object doBody() throws IOException {
SegmentInfos infos = new SegmentInfos();
infos.read(directory);
if (infos.size() == 1) { // index is optimized
return new SegmentReader(infos, infos.info(0),
closeDirectory);
} else {
IndexReader[] readers = new IndexReader[infos.size()];
for (int i = 0; i < infos.size(); i++) {
for(int j=0;j<oldreaders.length;j++) {
SegmentReader sr = (SegmentReader) oldreaders[j];
if(sr.si.name.equals(infos.info(i).name)) {
readers[i]=sr;
stayopen[j]=true;
}
}
if(readers[i]==null)
readers[i] = new SegmentReader(infos.info(i));
}
for(int i=0;i<stayopen.length;i++)
if(!stayopen[i])
oldreaders[i].close();
return new MultiReader(directory, infos, closeDirectory,
readers);
}
}
}.run();
}
}
-----Original Message-----
From: Doug Cutting [mailto:[EMAIL PROTECTED]
Sent: Wednesday, January 04, 2006 12:30 PM
To: java-dev@lucene.apache.org
Subject: Re: indexreader refresh
Amol Bhutada wrote:
If I have a reader and searcher on a indexdata folder and another
indexwriter writing documents to the same indexdata folder, do I need to
close existing reader and searcher and create new so that newly indexed
data comes into search effect?
[ moved from user to dev list]
This is a frequent request. While opening an all-new IndexReader is
effective, it is not always efficient. It might be nice to support a
more efficient means of re-opening an index.
Perhaps we should add a few new IndexReader methods, as follows:
/** If <code>reader</code>'s index has not been changed, return
* <code>reader</code>, otherwise return a new [EMAIL PROTECTED] IndexReader}
* reading the new latest of the index
*/
public static IndexReader open(IndexReader reader) {
if (isCurrent()) {
// unchanged: return existing
return reader;
}
// try to incrementally create new reader
IndexReader result = reader.reopen(reader);
if (result != null) {
return result;
}
// punt, opening an entirely new reader
return IndexReader.open(reader.directory());
}
/** Return a new IndexReader reading the current state
* of the index, re-using reader's resources, or null if this
* is not possible.
*/
protected IndexReader reopen(IndexReader reader) {
return null;
}
Then we can add implementations of reopen to SegmentReader and
MultiReader that attempt to re-use the existing, already opened
segments. This should mostly be simple, but there are a few tricky
issues, like detecting whether an already-open segment has had
deletions, and deciding when to close obsolete segments.
Does this sound like it would make a good addition? Does someone want
to volunteer to implement it?
Doug
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