Oups, I added this comment to the wrong issue... too many open browser
tabs... :)
Michael Busch (JIRA) wrote:
[ https://issues.apache.org/jira/browse/LUCENE-1195?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12599297#action_12599297 ]
Michael Busch commented on LUCENE-1195:
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{quote}
Using the deprecated method would have the advantage that it (the whole wrapper
class in fact) would _have_ to be removed in 3.0.
{quote}
Thanks for reviewing! You're right, I will change it to use the deprecated
method and also deprecate the wrapper class itself.
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
Attachments: lucene-1195.patch, lucene-1195.patch, lucene-1195.patch
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.
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