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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">



<html>

  <head>

    <title>RECOLL: a personal text search system for

    Unix/Linux</title>

    <meta name="generator" content="HTML Tidy, see www.w3.org">

    <meta name="Author" content="Jean-Francois Dockes">

    <meta name="Description" content=

    "recoll is a simple full-text search system for unix and linux based on the powerful and mature xapian engine">

    <meta name="Keywords" content=

      "full text search,fulltext,desktop search,unix,linux,solaris,open source,free">

    <meta http-equiv="Content-language" content="en">

    <meta http-equiv="content-type" content=

    "text/html; charset=iso-8859-1">

    <meta name="robots" content="All,Index,Follow">

    <link type="text/css" rel="stylesheet" href="styles/style.css">

  </head>



  <body>



    <div class="rightlinks">

      <ul>

	<li><a href="index.html">Home</a></li>

	<li><a href="pics/index.html">Screenshots</a></li>

	<li><a href="download.html">Downloads</a></li>

	<li><a href="doc.html">Documentation</a></li>

      </ul>

    </div>



    <div class="content">



      <h1>Recoll: Indexing performance and index sizes</h1>



      <p>The time needed to index a given set of documents, and the

	resulting index size depend of many factors, such as file size

	and proportion of actual text content for the index size, cpu

	speed, available memory, average file size and format for the

	speed of indexing.</p>



      <p>We try here to give a number of reference points which can

	be used to roughly estimate the resources needed to create and

	store an index. Obviously, your data set will never fit one of

	the samples, so the results cannot be exactly predicted.</p>



      <p>The following data was obtained on a machine with a 1800 Mhz

	AMD Duron CPU, 768Mb of Ram, and a 7200 RPM 160 GBytes IDE

	disk, running Suse 10.1.</p>



      <p><b>recollindex</b> (version 1.8.2 with xapian 1.0.0) is

	executed with the default flush threshold value. 

	The process memory usage is the one given by <b>ps</b></p>



      <table border=1>

	<thead>

	  <tr>

	    <th>Data</th>

	    <th>Data size</th>

	    <th>Indexing time</th>

	    <th>Index size</th>

	    <th>Peak process memory usage</th>

	  </tr>

	<tbody>

	  <tr>

	    <td>Random pdfs harvested on Google</td>

	    <td>1.7 GB, 3564 files</td>

	    <td>27 mn</td>

	    <td>230 MB</td>

	    <td>225 MB</td>

	  </tr>

	  <tr>

	    <td>Ietf mailing list archive</td>

	    <td>211 MB, 44,000 messages</td>

	    <td>8 mn</td>

	    <td>350 MB</td>

	    <td>90 MB</td>

	  </tr>

	  <tr>

	    <td>Partial Wikipedia dump</td>

	    <td>15 GB, one million files</td>

	    <td>6H30</td>

	    <td>10 GB</td>

	    <td>324 MB</td>

	  </tr>

	  <tr>

	    <!-- DB: ndocs 3564 lastdocid 3564 avglength 6460.71 -->

	    <td>Random pdfs harvested on Google<br>

	    Recoll 1.9, <em>idxflushmb</em> set to 10</td>

	    <td>1.7 GB, 3564 files</td>

	    <td>25 mn</td>

	    <td>262 MB</td>

	    <td>65 MB</td>

	  </tr>

	</tbody>

      </table>



      <p>Notice how the index size for the mail archive is bigger than

	the data size. Myriads of small pure text documents will do

	this. The factor of expansion would be even much worse with

	compressed folders of course (the test was on uncompressed

	data).</p>



      <p>The last test was performed with Recoll 1.9.0 which has an

	ajustable flush threshold (<em>idxflushmb</em> parameter), here

	set to 10 MB. Notice the much lower peak memory usage, with no

	performance degradation. The resulting index is bigger though,

	the exact reason is not known to me, possibly because of

	additional fragmentation </p>

      </p>



    </div>

  </body>

</html>