Compressors

This section explains how to configure WiredTiger's builtin support for the snappy and bzip2 compression engines.

Using zlib compression

To use the builtin support for Greg Roelofs' and Mark Adler's zlib 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 –enable-zlib option to configure.

If zlib is installed in a location not normally searched by the compiler toolchain, you'll need to modify the CPPFLAGS and LDFLAGS to indicate these locations. For example, with the zlib includes and libraries installed in /usr/local/include and /usr/local/lib, you would run configure with the following additional arguments:

--enable-zlib CPPFLAGS="-I/usr/local/include" LDFLAGS="-L/usr/local/include"

When opening the WiredTiger database, load the zlib shared library as an extension. For example, with the WiredTiger library installed in /usr/local/lib, you would use the following extension:

        ret = wiredtiger_open(home, NULL,
            "create,"
            "extensions=[/usr/local/lib/libwiredtiger_zlib.so]", &conn);

Finally, when creating the WiredTiger object, set block_compressor to zlib:

        ret = session->create(session,
            "table:mytable",
            "block_compressor=zlib,key_format=S,value_format=S");

Using snappy compression

To use the builtin support for Google's snappy 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 –enable-snappy option to configure.

If snappy is installed in a location not normally searched by the compiler toolchain, you'll need to modify the CPPFLAGS and LDFLAGS to indicate these locations. For example, with the snappy includes and libraries installed in /usr/local/include and /usr/local/lib, you would run configure with the following additional arguments:

--enable-snappy CPPFLAGS="-I/usr/local/include" LDFLAGS="-L/usr/local/include"

When opening the WiredTiger database, load the snappy shared library as an extension. For example, with the WiredTiger library installed in /usr/local/lib, you would use the following extension:

        ret = wiredtiger_open(home, NULL,
            "create,"
            "extensions=[/usr/local/lib/libwiredtiger_snappy.so]", &conn);

Finally, when creating the WiredTiger object, set block_compressor to snappy:

        ret = session->create(session,
            "table:mytable",
            "block_compressor=snappy,key_format=S,value_format=S");

Using bzip2 compression

To use the builtin support for Julian Seward's bzip2 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 –enable-bzip2 option to configure.

If bzip2 is installed in a location not normally searched by the compiler toolchain, you'll need to modify the CPPFLAGS and LDFLAGS to indicate these locations. For example, with the bzip2 includes and libraries installed in /usr/local/include and /usr/local/lib, you would run configure with the following additional arguments:

--enable-bzip2 CPPFLAGS="-I/usr/local/include" LDFLAGS="-L/usr/local/include"

When opening the WiredTiger database, load the bzip2 shared library as an extension. For example, with the WiredTiger library installed in /usr/local/lib, you would use the following extension:

        ret = wiredtiger_open(home, NULL,
            "create,"
            "extensions=[/usr/local/lib/libwiredtiger_bzip2.so]", &conn);

Finally, when creating the WiredTiger object, set block_compressor to bzip2:

        ret = session->create(session,
            "table:mytable",
            "block_compressor=bzip2,key_format=S,value_format=S");

Upgrading compression engines

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.

Custom compression engines

WiredTiger may be extended by adding custom compression engines; see WT_COMPRESSOR for more information.