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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 lz4, snappy, zlib and zstd compression engines.</p>
<h1><a class="anchor" id="compression_lz4"></a>
Using LZ4 compression</h1>
<p>To use the builtin support for Yann Collet's <a href="https://github.com/Cyan4973/lz4">LZ4</a> compression, first check that LZ4 is installed in include and library directories searched by the compiler. Once LZ4 is installed, you can enable LZ4 using the <code>–enable-lz4</code> option to configure.</p>
<p>If LZ4 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 LZ4 includes and libraries installed in <code>/usr/local/include</code> and <code>/usr/local/lib</code>, you would run configure with the following additional arguments:</p>
<div class="fragment"><div class="line">--enable-lz4 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 LZ4 shared library as an extension. For example, with the WiredTiger library installed in <code>/usr/local/lib</code>, you would use the following extension:</p>
<div class="fragment"><div class="line"> error_check(<a class="code" href="group__wt.html#gacbe8d118f978f5bfc8ccb4c77c9e8813">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/libwiredtiger_lz4.so]"</span>, &conn));</div></div><!-- fragment --><p> Finally, when creating the WiredTiger object, set <code>block_compressor</code> to <code>lz4:</code> </p>
<div class="fragment"><div class="line"> error_check(session-><a class="code" href="struct_w_t___s_e_s_s_i_o_n.html#a358ca4141d59c345f401c58501276bbb">create</a>(session,</div><div class="line"> <span class="stringliteral">"table:mytable"</span>,</div><div class="line"> <span class="stringliteral">"block_compressor=lz4,key_format=S,value_format=S"</span>));</div></div><!-- fragment --> <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 would run configure with the following additional arguments:</p>
<div class="fragment"><div class="line">--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 WiredTiger library installed in <code>/usr/local/lib</code>, you would use the following extension:</p>
<div class="fragment"><div class="line"> error_check(<a class="code" href="group__wt.html#gacbe8d118f978f5bfc8ccb4c77c9e8813">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/libwiredtiger_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"> error_check(session-><a class="code" href="struct_w_t___s_e_s_s_i_o_n.html#a358ca4141d59c345f401c58501276bbb">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 --> <h1><a class="anchor" id="compression_zlib"></a>
Using zlib compression</h1>
<p>To use the builtin support for Greg Roelofs' and Mark Adler's <a href="http://www.zlib.net/">zlib</a> compression, first check that zlib is installed in include and library directories searched by the compiler. Once zlib is installed, you can enable zlib using the <code>–enable-zlib</code> option to configure.</p>
<p>If zlib 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 zlib includes and libraries installed in <code>/usr/local/include</code> and <code>/usr/local/lib</code>, you would run configure with the following additional arguments:</p>
<div class="fragment"><div class="line">--enable-zlib 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 zlib shared library as an extension. For example, with the WiredTiger library installed in <code>/usr/local/lib</code>, you would use the following extension:</p>
<div class="fragment"><div class="line"> error_check(<a class="code" href="group__wt.html#gacbe8d118f978f5bfc8ccb4c77c9e8813">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/libwiredtiger_zlib.so]"</span>, &conn));</div></div><!-- fragment --><p> The default compression level for the zlib compression is <code>Z_DEFAULT_COMPRESSION</code> (see the zlib documentation for further information); compression can be configured to other levels using the additional configuration argument <code>compression_level</code>.</p>
<div class="fragment"><div class="line"> error_check(<a class="code" href="group__wt.html#gacbe8d118f978f5bfc8ccb4c77c9e8813">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/"</span></div><div class="line"> <span class="stringliteral">"libwiredtiger_zlib.so=[config=[compression_level=3]]]"</span>, &conn));</div></div><!-- fragment --><p> Finally, when creating the WiredTiger object, set <code>block_compressor</code> to <code>zlib:</code> </p>
<div class="fragment"><div class="line"> error_check(session-><a class="code" href="struct_w_t___s_e_s_s_i_o_n.html#a358ca4141d59c345f401c58501276bbb">create</a>(session,</div><div class="line"> <span class="stringliteral">"table:mytable"</span>,</div><div class="line"> <span class="stringliteral">"block_compressor=zlib,key_format=S,value_format=S"</span>));</div></div><!-- fragment --> <h1><a class="anchor" id="compression_zstd"></a>
Using Zstd compression</h1>
<p>To use the builtin support for Facebook's <a href="https://github.com/facebook/zstd">Zstd</a> compression, first check that Zstd is installed in include and library directories searched by the compiler. Once Zstd is installed, you can enable Zstd using the <code>–enable-zstd</code> option to configure.</p>
<p>If Zstd 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 Zstd includes and libraries installed in <code>/usr/local/include</code> and <code>/usr/local/lib</code>, you would run configure with the following additional arguments:</p>
<div class="fragment"><div class="line">--enable-zstd 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 Zstd shared library as an extension. For example, with the WiredTiger library installed in <code>/usr/local/lib</code>, you would use the following extension:</p>
<div class="fragment"><div class="line"> error_check(<a class="code" href="group__wt.html#gacbe8d118f978f5bfc8ccb4c77c9e8813">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/libwiredtiger_zstd.so]"</span>, &conn));</div></div><!-- fragment --><p> The default compression level for the zstd compression is 3; compression can be configured to other levels using the additional configuration argument <code>compression_level</code>.</p>
<div class="fragment"><div class="line"> error_check(<a class="code" href="group__wt.html#gacbe8d118f978f5bfc8ccb4c77c9e8813">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/"</span></div><div class="line"> <span class="stringliteral">"libwiredtiger_zstd.so=[config=[compression_level=9]]]"</span>, &conn));</div></div><!-- fragment --><p> Finally, when creating the WiredTiger object, set <code>block_compressor</code> to <code>zstd:</code> </p>
<div class="fragment"><div class="line"> error_check(session-><a class="code" href="struct_w_t___s_e_s_s_i_o_n.html#a358ca4141d59c345f401c58501276bbb">create</a>(session,</div><div class="line"> <span class="stringliteral">"table:mytable"</span>,</div><div class="line"> <span class="stringliteral">"block_compressor=zstd,key_format=S,value_format=S"</span>));</div></div><!-- fragment --> <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" title="The interface implemented by applications to provide custom compression. ">WT_COMPRESSOR</a> for more information. </p>
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