Various notes and links on Lucene¶

• Table of contents
• Various notes and links on Lucene
  • • Joins in Lucene
      • joins using BlockJoinQuery
      • joins using the JoinUtil
    • Filters
      • General rules
      • Links to docs

Joins in Lucene¶

joins using BlockJoinQuery¶

• possible since v3.4.0

• http://blog.mikemccandless.com/2012/01/searching-relational-content-with.html

joins using the JoinUtil¶

is slower than BlockJoinQuery but seems more flexible and does not require special indexing

• possisble since 3.6, 4.0-ALPHA

• https://issues.apache.org/jira/browse/LUCENE-3602

• http://lucene.apache.org/core/3_6_2/api/all/org/apache/lucene/search/join/JoinUtil.html

Filters¶

General rules¶

• I you are using multiple filters, place these filters inside of a Boolean Filter. The Boolean Filter internally benefits from the BitSets produced by Filters.

• If you need to use And/Or/Not Filters, your “heaviest” filter should always be placed last – typically Geo filters since they can perform some heavy computations to determine distance.

• And/Or/Not are more performant when you are working with filters that do not return a bitset. These are operations that must iterate over every document anyway. For example, a custom script is not BitSet-able because it performs computation on every document. In these cases, And/Or/Not is a better choice than the Bool. The list of Non-Bitset filters is very small, so it is easy to remember.( That’s it! Every other filter should be placed inside of a Bool):

  • Geo* filters
  • Scripts
  • Numeric_range

Links to docs¶

• on bitsets and filters: http://www.elasticsearch.org/blog/all-about-elasticsearch-filter-bitsets/