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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<div class="title">Compressors </div> </div>
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<div class="textblock"><p>This section explains how to configure WiredTiger's builtin support for the bzip2 and snappy compression engines.</p>
<h1><a class="anchor" id="compression_bzip2"></a>
Using bzip2 compression</h1>
<p>To use the builtin support for <a href="http://www.bzip.org/">Julian Seward's bzip2</a> compression, first check that bzip2 is installed in include and library directories searched by the compiler. Once bzip2 is installed, you can enable bzip2 using the <code>–enable-bzip2</code> option to configure.</p>
<p>If bzip2 is installed in a location not normally searched by the compiler toolchain, you'll need to modify the <code>CPPFLAGS</code> and <code>LDFLAGS</code> to indicate these locations. For example, with the bzip2 includes and libraries installed in <code>/usr/local/include</code> and <code>/usr/local/lib</code>, you should run configure as follows:</p>
<div class="fragment"><div class="line">cd build_posix</div>
<div class="line">../configure --enable-bzip2 CPPFLAGS=<span class="stringliteral">"-I/usr/local/include"</span> LDFLAGS=<span class="stringliteral">"-L/usr/local/include"</span></div>
</div><!-- fragment --><p>When opening the WiredTiger database, load the bzip2 shared library as an extension. For example, with the bzip2 library installed in <code>/usr/local/lib</code>, you would use the following extension:</p>
<div class="fragment"><div class="line"> <a class="code" href="struct_w_t___c_o_n_n_e_c_t_i_o_n.html" title="A connection to a WiredTiger database.">WT_CONNECTION</a> *conn;</div>
<div class="line"></div>
<div class="line"> ret = <a class="code" href="group__wt.html#ga9e6adae3fc6964ef837a62795c7840ed" title="Open a connection to a database.">wiredtiger_open</a>(home, NULL,</div>
<div class="line"> <span class="stringliteral">"create,"</span></div>
<div class="line"> <span class="stringliteral">"extensions=[\"/usr/local/lib/wiredtiger_bzip2.so\"]"</span>, &conn);</div>
</div><!-- fragment --><p> Finally, when creating the WiredTiger object, set <code>block_compressor</code> to <code>bzip2:</code> </p>
<div class="fragment"><div class="line"> ret = session-><a class="code" href="struct_w_t___s_e_s_s_i_o_n.html#a358ca4141d59c345f401c58501276bbb" title="Create a table, column group, index or file.">create</a>(session,</div>
<div class="line"> <span class="stringliteral">"table:mytable"</span>,</div>
<div class="line"> <span class="stringliteral">"block_compressor=bzip2,key_format=S,value_format=S"</span>);</div>
</div><!-- fragment --><p> If necessary, you can confirm the compressor is working by running the compression part of the test suite:</p>
<div class="fragment"><div class="line">cd build_posix</div>
<div class="line">python ../test/suite/run.py compress</div>
</div><!-- fragment --><p>Review the test output to verify the bzip2 part of the test passes and was not skipped.</p>
<h1><a class="anchor" id="compression_snappy"></a>
Using snappy compression</h1>
<p>To use the builtin support for <a href="http://code.google.com/p/snappy/">Google's snappy</a> compression, first check that snappy is installed in include and library directories searched by the compiler. Once snappy is installed, you can enable snappy using the <code>–enable-snappy</code> option to configure.</p>
<p>If snappy is installed in a location not normally searched by the compiler toolchain, you'll need to modify the <code>CPPFLAGS</code> and <code>LDFLAGS</code> to indicate these locations. For example, with the snappy includes and libraries installed in <code>/usr/local/include</code> and <code>/usr/local/lib</code>, you should run configure as follows:</p>
<div class="fragment"><div class="line">cd build_posix</div>
<div class="line">../configure --enable-snappy CPPFLAGS=<span class="stringliteral">"-I/usr/local/include"</span> LDFLAGS=<span class="stringliteral">"-L/usr/local/include"</span></div>
</div><!-- fragment --><p>When opening the WiredTiger database, load the snappy shared library as an extension. For example, with the snappy library installed in <code>/usr/local/lib</code>, you would use the following extension:</p>
<div class="fragment"><div class="line"> <a class="code" href="struct_w_t___c_o_n_n_e_c_t_i_o_n.html" title="A connection to a WiredTiger database.">WT_CONNECTION</a> *conn;</div>
<div class="line"></div>
<div class="line"> ret = <a class="code" href="group__wt.html#ga9e6adae3fc6964ef837a62795c7840ed" title="Open a connection to a database.">wiredtiger_open</a>(home, NULL,</div>
<div class="line"> <span class="stringliteral">"create,"</span></div>
<div class="line"> <span class="stringliteral">"extensions=[\"/usr/local/lib/wiredtiger_snappy.so\"]"</span>, &conn);</div>
</div><!-- fragment --><p> Finally, when creating the WiredTiger object, set <code>block_compressor</code> to <code>snappy:</code> </p>
<div class="fragment"><div class="line"> ret = session-><a class="code" href="struct_w_t___s_e_s_s_i_o_n.html#a358ca4141d59c345f401c58501276bbb" title="Create a table, column group, index or file.">create</a>(session,</div>
<div class="line"> <span class="stringliteral">"table:mytable"</span>,</div>
<div class="line"> <span class="stringliteral">"block_compressor=snappy,key_format=S,value_format=S"</span>);</div>
</div><!-- fragment --><p> If necessary, you can confirm the compressor is working by running the compression part of the test suite:</p>
<div class="fragment"><div class="line">cd build_posix</div>
<div class="line">python ../test/suite/run.py compress</div>
</div><!-- fragment --><p>Review the test output to verify the snappy part of the test passes and was not skipped.</p>
<h1><a class="anchor" id="compression_upgrading"></a>
Upgrading compression engines</h1>
<p>WiredTiger does not store information with file blocks to identify the compression engine used to compressed the block. Applications wanting to upgrade to some future compression engine (without requiring a file dump and re-load), should ensure each compressed block includes enough information to identify the compression engine used, so its compression code can correctly decompress old and new blocks.</p>
<h1><a class="anchor" id="compression_custom"></a>
Custom compression engines</h1>
<p>WiredTiger may be extended by adding custom compression engines; see <a class="el" href="struct_w_t___c_o_m_p_r_e_s_s_o_r.html">WT_COMPRESSOR</a> for more information. </p>
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