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From "Yonik Seeley" <>
Subject Re: FieldsReader synchronized access vs. ThreadLocal ?
Date Wed, 17 May 2006 18:35:37 GMT
On 5/17/06, Robert Engels <> wrote:
> Since reading a document is a relatively expensive operation

Expensive relative to searching operations that cover 1 million
documents (i.e. you don't want to call doc() a million times)

Solr has a document cache, and I've found that it doesn't help max
throughput that much (I just needed more concurrent searchers to reach
the max), but it does help latency of individual requests.

>[...] Since the
> isDeleted() method uses the same synchronized lock as document(), all query
> scorers that filter out deleted documents will also be impacted, as they
> will block while the document is being read.

Interesting observation... that lock need not be shared.
Using a different lock would mean aquiring two locks per doc() call,
but it may be worth it to unblock the scorers waiting on isDeleted()

It might also be worth it to make a ReadOnlyIndexReader that didn't
have to deal with issues of synchronizing access to the deleted docs

If only Sun had done their APIs correctly, we could easily make
non-synchronizing implementations of IndexInput and friends w/o
resorting to ThreadLocals... Ah well.

-Yonik Solr, the open-source Lucene search server

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