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Lucene 8.4.0 misc API

Misc Tools

See: Description

Package Description
Misc extensions of the Document/Field API.
Misc index tools and index support.
Miscellaneous index tools.
Misc search implementations.
Misc similarity implementations.
Misc Directory implementations.
Memory Tracker interface which allows defining custom collector level memory trackers
Misc FST classes.

Misc Tools

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


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

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:

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.

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