Mailing-List: contact java-dev-help@lucene.apache.org; run by ezmlm
Precedence: bulk
Reply-To: java-dev@lucene.apache.org
Message-ID: <1456546029.1204074892068.JavaMail.jira@brutus>
Date: Tue, 26 Feb 2008 17:14:52 -0800 (PST)
From: "Yonik Seeley (JIRA)" <jira@apache.org>
To: java-dev@lucene.apache.org
Subject: [jira] Commented: (LUCENE-1195) Performance improvement for
 TermInfosReader
In-Reply-To: <222260612.1204066852510.JavaMail.jira@brutus>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit


    [ https://issues.apache.org/jira/browse/LUCENE-1195?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12572753#action_12572753 ] 

Yonik Seeley commented on LUCENE-1195:
--------------------------------------

Thinking about a common use in Solr: doing a query and faceting that query by a field... would blow out the cache (due to iterating over all the terms in a single field) if it's a global cache?  Is there a good way to prevent that from happening (perhaps just change lucene's existing single -entry thread local cache to a multi-entry thread local cache?)

> Performance improvement for TermInfosReader
> -------------------------------------------
>
>                 Key: LUCENE-1195
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1195
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>            Reporter: Michael Busch
>            Assignee: Michael Busch
>            Priority: Minor
>             Fix For: 2.4
>
>
> Currently we have a bottleneck for multi-term queries: the dictionary lookup is being done
> twice for each term. The first time in Similarity.idf(), where searcher.docFreq() is called.
> The second time when the posting list is opened (TermDocs or TermPositions).
> The dictionary lookup is not cheap, that's why a significant performance improvement is
> possible here if we avoid the second lookup. An easy way to do this is to add a small LRU 
> cache to TermInfosReader. 
> I ran some performance experiments with an LRU cache size of 20, and an mid-size index of
> 500,000 documents from wikipedia. Here are some test results:
> 50,000 AND queries with 3 terms each:
> old:                  152 secs
> new (with LRU cache): 112 secs (26% faster)
> 50,000 OR queries with 3 terms each:
> old:                  175 secs
> new (with LRU cache): 133 secs (24% faster)
> For bigger indexes this patch will probably have less impact, for smaller once more.
> I will attach a patch soon.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.


---------------------------------------------------------------------
To unsubscribe, e-mail: java-dev-unsubscribe@lucene.apache.org
For additional commands, e-mail: java-dev-help@lucene.apache.org