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From Geoffrey Peddle <tryluc...@yahoo.ca>
Subject Benchmark: Lucene vs commercial search engine
Date Mon, 22 Dec 2003 20:10:32 GMT
I'm doing a technical evaluation of search engines 
for Ariba, an enterprise application software company.
 I compared Lucene to a commercial C language based
search engine which I'll refer to as vendor A.  
Overall Lucene's performance was similar to vendor A
and met our application's requirements.  I've
summarized our results below.
 

Search scalability:

We ran a set of 16 queries in a single thread for 20
iterations.  We report below the times for the last 15
iterations (ie after the system was warmed up).   The
4 sets of results below are for indexes with between
50,000 documents to 600,000 documents.  Although the
times for Lucene grew faster with document count than
vendor A they were comparable.

50K  documents
Lucene   5.2   seconds
A        7.2

200K
Lucene   15.3
A        15.2

400K
Lucene    28.2
A         25.5

600K
Lucene    41
A         33


Individual Query times:

Total query times are very similar between the 2
systems but there were larger differences when you
looked at individual queries.

For simple queries with small result sets Vendor A was
consistently faster than Lucene.   For example a
single query might take vendor A 32 thousands of a
second and Lucene 64 thousands of a second.    Both
times are however well within acceptable response
times for our application.

For simple queries with large result sets Vendor A was
consistently slower than Lucene.   For example a
single query might take vendor A 300 thousands of a
second and Lucene 200 thousands of a second.

For more complex queries of the form   (term1 or term2
or term3)  AND (term4 or term5 or term6) AND (term7 or
term8)    the results were more divergent.  For
queries with small result sets Vendor A generally had
very short response times and sometimes Lucene had
significantly larger response times.  For example
Vendor A might take 16 thousands of a second and
Lucene might take 156.   I do not consider it to be
the case that Lucene's response time grew unexpectedly
but rather that Vendor A appeared to be taking
advantage of an optimization which Lucene didn't have.
  (I believe there's been discussions on the dev
mailing list on complex queries of this sort.)

 
Index Size:

For our test data the size of both indexes grew
linearly with the number of documents.   Note that
these sizes are compact sizes, not maximum size during
index loading.   The numbers below are from running du
-k in the directory containing the index data.   The
larger number's below for Vendor A may be because it
supports additional functionality not available in
Lucene.   I think it's the constant rate of growth
rather than the absolute amount which is more
important.

50K  documents
Lucene      45516 K
A           63921

200K
Lucene      171565
A           228370

400K
Lucene      345717
A           457843

600K
Lucene      511338
A           684913
 

Indexing Times:

These times are for reading the documents from our
database, processing them, inserting them into the
document search product and index compacting.   Our
data has a large number of fields/attributes.   For
this test I restricted Lucene to 24 attributes to
reduce the number of files created.  Doing this I was
able to specify a merge width for Lucene of 60.   I
found in general that Lucene indexing performance to
be very sensitive to changes in the merge width.  
Note also that our application does a full compaction
after inserting every 20,000 documents.   These times
are just within our acceptable limits but we are
interested in alternatives to increase Lucene's
performance in this area.

600K documents
Lucene       81 minutes
A            34 minutes

(I don't have accurate results for all sizes on this
measure but believe that the indexing time for both
solutions grew essentially linearly with size.   The
time to compact the index generally grew with index
size but it's a small percent of overall time at these
sizes.)

-Geoffrey




  <benchmark>
  <ul>
  <p>
  <b>Hardware Environment</b> 
  <br /> 
  <li>
  <i>Dedicated machine for indexing</i> 
  : yes 
  </li>
  <li>
  <i>CPU</i> 
  : Dell PentiumŪ 4 CPU 2.00Ghz,   1cpu
  </li>
  <li>
  <i>RAM</i> 
  : 1 Gig 
  </li>
  <li>
  <i>Drive configuration</i> 
  : Fujitsu MAM3367MP SCSI 
  </li>
  </p>
  <p>
  <b>Software environment</b> 
  <br /> 
  <li>
  <i>Java Version</i> 
  : JDK 1.4.2_02
  </li>
  <li>
  <i>Java VM</i> 
  :
  </li>
  <li>
  <i>OS Version</i> 
  : Windows XP 
  </li>
  <li>
  <i>Location of index</i> 
  : Local file system 
  </li>
  </p>
  <p>
  <b>Lucene indexing variables</b> 
  <br /> 
  <li>
  <i>Number of source documents</i> 
  600,000
  </li>
  <li>
  <i>Total filesize of source documents</i> 
  : from database
  </li>
  <li>
  <i>Average filesize of source documents</i> 
  : from database
  </li>
  <li>
  <i>Source documents storage location</i> 
  : DB
  </li>
  <li>
  <i>File type of source documents</i> 
  : XML
  </li>
  <li>
  <i>Parser(s) used, if any</i> 
  : None
  </li>
  <li>
  <i>Analyzer(s) used</i> 
  : small variation on WhitespaceAnalyzer
  </li>
  <li>
  <i>Number of fields per document</i> 
  : 24
  </li>
  <li>
  <i>Type of fields</i> 
  : 1 keyword, 1 big unindexed, rest are unstored and
a mix of tokenized/untokenized
  </li>
  <li>
  <i>Index persistence</i> 
  :  FSDirectory
  </li>
  </p>
  <p>
  <b>Figures</b> 
  <br /> 
  <li>
  <i>Time taken (in ms/s as an average of at least 3
indexing runs)</i> 
  : 600,000 documents in 81 minutes   (du -k = 511338)
  </li>
  <li>
  <i>Time taken / 1000 docs indexed</i> 
  : 123 documents/second
  </li>
  <li>
  <i>Memory consumption</i> 
  : -ms256m -mx512m -Xss4m -XX:MaxPermSize=512M
  </li>
  </p>
  <p>
  <b>Notes</b> 
  <br /> 
  <li>
  <i>Notes</i> 
  : merge width of 60. 
  : did a compact every 20,000 documents
  </li>
  </p>
  </ul>
  </benchmark>


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