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| <h1 id="Lucene_Net_Misc" data-uid="Lucene.Net.Misc" class="text-break">Namespace Lucene.Net.Misc |
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| <h2 id="misc-tools">Misc Tools</h2> |
| <p>The misc package has various tools for splitting/merging indices, |
| changing norms, finding high freq terms, and others.</p> |
| <h2 id="nativeunixdirectory">NativeUnixDirectory</h2> |
| <p><strong>NOTE</strong>: This uses C++ sources (accessible via JNI), which you'll |
| have to compile on your platform.</p> |
| <p><xref:Lucene.Net.Store.NativeUnixDirectory> is a Directory implementation that bypasses the |
| OS's buffer cache (using direct IO) for any IndexInput and IndexOutput |
| used during merging of segments larger than a specified size (default |
| 10 MB). This avoids evicting hot pages that are still in-use for |
| searching, keeping search more responsive while large merges run.</p> |
| <p>See <a href="http://blog.mikemccandless.com/2010/06/lucene-and-fadvisemadvise.html">this blog post</a> |
| for details.</p> |
| <p>Steps to build:</p> |
| <ul> |
| <li><tt>cd lucene/misc/</tt> |
| |
| </li> |
| <li><p>To compile NativePosixUtil.cpp -> libNativePosixUtil.so, run<tt> ant build-native-unix</tt>.</p> |
| </li> |
| <li><p><tt>libNativePosixUtil.so</tt> will be located in the <tt>lucene/build/native/</tt> folder</p> |
| </li> |
| <li><p>Make sure libNativePosixUtil.so is on your LD_LIBRARY_PATH so java can find it (something like <tt>export LD_LIBRARY_PATH=/path/to/dir:$LD_LIBRARY_PATH</tt>, where /path/to/dir contains libNativePosixUtil.so)</p> |
| </li> |
| <li><p><tt>ant jar</tt> to compile the java source and put that JAR on your CLASSPATH</p> |
| </li> |
| </ul> |
| <p>NativePosixUtil.cpp/java also expose access to the posix_madvise, |
| madvise, posix_fadvise functions, which are somewhat more cross |
| platform than O_DIRECT, however, in testing (see above link), these |
| APIs did not seem to help prevent buffer cache eviction.</p> |
| </div> |
| <div class="markdown level0 conceptual"></div> |
| <div class="markdown level0 remarks"></div> |
| <h3 id="classes">Classes |
| </h3> |
| <h4><a class="xref" href="Lucene.Net.Misc.GetTermInfo.html">GetTermInfo</a></h4> |
| <section><p>Utility to get document frequency and total number of occurrences (sum of the tf for each doc) of a term. </p> |
| </section> |
| <h4><a class="xref" href="Lucene.Net.Misc.HighFreqTerms.html">HighFreqTerms</a></h4> |
| <section><p><a class="xref" href="Lucene.Net.Misc.HighFreqTerms.html">HighFreqTerms</a> class extracts the top n most frequent terms |
| (by document frequency) from an existing Lucene index and reports their |
| document frequency. |
| <p> |
| If the -t flag is given, both document frequency and total tf (total |
| number of occurrences) are reported, ordered by descending total tf.</p> |
| <p> |
| </section> |
| <h4><a class="xref" href="Lucene.Net.Misc.HighFreqTerms.DocFreqComparer.html">HighFreqTerms.DocFreqComparer</a></h4> |
| <section><p>Compares terms by <a class="xref" href="Lucene.Net.Misc.TermStats.html#Lucene_Net_Misc_TermStats_DocFreq">DocFreq</a></p> |
| </section> |
| <h4><a class="xref" href="Lucene.Net.Misc.HighFreqTerms.TotalTermFreqComparer.html">HighFreqTerms.TotalTermFreqComparer</a></h4> |
| <section><p>Compares terms by <a class="xref" href="Lucene.Net.Misc.TermStats.html#Lucene_Net_Misc_TermStats_TotalTermFreq">TotalTermFreq</a> </p> |
| </section> |
| <h4><a class="xref" href="Lucene.Net.Misc.IndexMergeTool.html">IndexMergeTool</a></h4> |
| <section><p>Merges indices specified on the command line into the index |
| specified as the first command line argument.</p> |
| </section> |
| <h4><a class="xref" href="Lucene.Net.Misc.SweetSpotSimilarity.html">SweetSpotSimilarity</a></h4> |
| <section><p> |
| A similarity with a lengthNorm that provides for a "plateau" of |
| equally good lengths, and tf helper functions. |
| </p> |
| <p> |
| For lengthNorm, A min/max can be specified to define the |
| plateau of lengths that should all have a norm of 1.0. |
| Below the min, and above the max the lengthNorm drops off in a |
| sqrt function. |
| </p> |
| <p> |
| For tf, baselineTf and hyperbolicTf functions are provided, which |
| subclasses can choose between. |
| </p> |
| </section> |
| <h4><a class="xref" href="Lucene.Net.Misc.TermStats.html">TermStats</a></h4> |
| <section><p>Holder for a term along with its statistics |
| (<a class="xref" href="Lucene.Net.Misc.TermStats.html#Lucene_Net_Misc_TermStats_DocFreq">DocFreq</a> and <a class="xref" href="Lucene.Net.Misc.TermStats.html#Lucene_Net_Misc_TermStats_TotalTermFreq">TotalTermFreq</a>).</p> |
| </section> |
| </article> |
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