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Apache Lucene

Apache Lucene is a high-performance, full-featured text search engine library written entirely in Java. It is a technology suitable for nearly any application that requires full-text search, especially cross-platform. Apache Lucene is an open source project available for free download.

Apache Lucene Homepage

JanusGraph supports Apache Lucene as a single-machine, embedded index backend. Lucene has a slightly extended feature set and performs better in small-scale applications compared to Elasticsearch, but is limited to single-machine deployments.

Lucene Embedded Configuration

For single machine deployments, Lucene runs embedded with JanusGraph. JanusGraph starts and interfaces with Lucene internally.

To run Lucene embedded, add the following configuration options to the graph configuration file where /data/searchindex specifies the directory where Lucene should store the index data:

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index.search.backend=lucene
index.search.directory=/data/searchindex

In the above configuration, the index backend is named search. Replace search by a different name to change the name of the index.

Feature Support

  • Full-Text: Supports all Text predicates to search for text properties that matches a given word, prefix or regular expression.
  • Geo: Supports Geo predicates to search for geo properties that are intersecting, within, or contained in a given query geometry. Supports points, lines and polygons for indexing. Supports circles and boxes for querying point properties and all shapes for querying non-point properties.
  • Numeric Range: Supports all numeric comparisons in Compare.
  • Temporal: Nanosecond granularity temporal indexing.
  • Custom Analyzer: Choose to use a custom analyzer
  • Not Query-normal-form: Supports queries other than Query-normal-form (QNF). QNF for JanusGraph is a variant of CNF (conjunctive normal form) with negation inlined where possible.

Configuration Options

Refer to Configuration Reference for a complete listing of all Lucene specific configuration options in addition to the general JanusGraph configuration options.

Note, that each of the index backend options needs to be prefixed with index.[INDEX-NAME]. where [INDEX-NAME] stands for the name of the index backend. For instance, if the index backend is named search then these configuration options need to be prefixed with index.search.. To configure an index backend named search to use Lucene as the index system, set the following configuration option:

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index.search.backend=lucene

Further Reading