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cene.lucene-misc.6.2.1.source-code.overview.html Maven / Gradle / Ivy

  
    
  
  

Misc Tools

The misc package has various tools for splitting/merging indices,
changing norms, finding high freq terms, and others.


NativeUnixDirectory


NOTE: This uses C++ sources (accessible via JNI), which you'll
have to compile on your platform.


{@link org.apache.lucene.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.


See this blog post
for details.

Steps to build:

  
 cd lucene/misc/

  
 To compile NativePosixUtil.cpp -> libNativePosixUtil.so, run ant build-native-unix.
  
  
libNativePosixUtil.so will be located in the lucene/build/native/ folder

  
 Make sure libNativePosixUtil.so is on your LD_LIBRARY_PATH so java can find it (something like export LD_LIBRARY_PATH=/path/to/dir:$LD_LIBRARY_PATH, where /path/to/dir contains libNativePosixUtil.so)

  
 ant jar to compile the java source and put that JAR on your CLASSPATH



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.