You need to keep a reader open so long as you plan to use any of its
methods from any thread.
The reader does close exactly when you ask it to (when you call
reader.close()).
You should not have to "open a new reader for every method call" --
you only need to open a new reader (and in your case, RAMDirectory)
whenever the underlying index has changed.
Mike
Ruslan Sivak wrote:
Thank you to everyone for your comments. I didn't realize that
readers need to be kept open and won't close exactly when you ask
them too. I have restructured my code to keep the RamDirectory
cached, and to open a new reader for every method call. This seems
to be working fine.
Russ
Erick Erickson wrote:
Even if you could tell a reader is closed, you'd wind up with
unmaintainable code. I envision you have a bunch of places
where you'd do something like
if (reader.isClosed()) {
reader = create a new reader.
}
But practically, you'd be opening a new reader someplace,
closing it someplace else, opening it in another place......
This just leads to maintenance nightmares. For instance, how
could you determine what the state of a particular reader was
when trying to figure out why your searches didn't work if you don't
have a clue where/when it was opened?
Perhaps the easiest thing to do if you can't restructure your code
as Michael suggested is just employ a singleton pattern to give you
complete control over when/where a reader is opened.....
Best
Erick
On Dec 12, 2007 5:36 AM, Michael McCandless
<[EMAIL PROTECTED]>
wrote:
Ruslan Sivak wrote:
Michael McCandless wrote:
Ruslan Sivak wrote:
I have an index of about 10mb. Since it's so small, I would like
to keep it loaded in memory, and reload it about every minute or
so, assuming that it has changed on disk. I have the following
code, which works, except it doesn't reload the changes.
protected String indexName;
protected IndexReader reader;
private long lastCheck=0;
...
protected IndexReader getReader() throws CorruptIndexException,
IOException
{
if (reader==null || System.currentTimeMillis() > lastCheck
+60000)
{
lastCheck=System.currentTimeMillis();
if (reader==null || !reader.isCurrent())
{
if (reader!=null)
reader.close();
Directory dir = new RAMDirectory
(indexName);
reader = IndexReader.open(dir);
searcher = new IndexSearcher(reader);
}
}
return reader;
}
Apparently reader.isCurrent() won't tell you if the underlying
FSDirectory has changed.
That's right: your reader is only searching the RAMDirectory; it
has no idea that your RAMDirectory was copied from an FSDirectory
that has now changed. (That ctor for RAMDirectory makes a full
copy of what's currently in the FSDirectory and thereafter
maintains no link to that FSDirectory).
I also had the following code before:
instead of
if (reader==null || !reader.isCurrent())
I had
if (reader==null || reader.getVersion() !=
IndexReader.getCurrentVersion(indexName))
That 2nd line seems like it should have worked. What version of
Lucene are you using? Are you really sure it's not showing the
changes? Can you print the two versions? Every commit to the
index (by IndexWriter) should increment that version number.
The 2nd line was working fine, however I was getting errors in
other places saying that the indexReader is closed.
Can you restructure your code, such that you open a new reader
without first closing the old one, and then only once the open is
complete, you swap the new reader in as "reader", wait for
threads to
finish using the old reader, then call close on the old one?
I was getting a bunch of this indexreader is closed errors, and
I'm not sure why there's no method like reader.isClosed().
That's spooky: can you explain why you're accidentally using a
closed reader? Your code above seems to replace reader after
closing it. Are there other threads that are using the reader
while you are doing this re-opening?
There could be other threads using this, and there are other places
in the code that open and close readers. My main problem I guess
is that I can't tell when a reader is closed. Is there some method
I can use? I basically want to do something like this.
if (reader==null || reader.isClosed || reader.getVersion() !=
IndexReader.getCurrentVersion(indexName))
There is currently no way to ask a reader if it's closed. I suppose
you could do something like:
try {
version = reader.getVersion();
isClosed = false;
} catch (AlreadyClosedException e) {
isClosed = true;
}
However this is somewhat bad form. It's better to restructure your
code such that it's not possible to accidentally use a reader you
had
closed.
Is reader threadsafe? Should each invocation open it's own reader?
Reader is definitely thread safe, so you should share 1 reader
across
all threads. You just need to take care in your app to not close a
reader if other threads are still using it or will continue using
it.
Mike
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