# Package org.apache.lucene.backward_codecs.lucene90.blocktree

package org.apache.lucene.backward_codecs.lucene90.blocktree
BlockTree terms dictionary.

This terms dictionary organizes all terms into blocks according to shared prefix, such that each block has enough terms, and then stores the prefix trie in memory as an FST as the index structure. It allows you to plug in your own `PostingsWriterBase` to implement the postings.

See org.apache.lucene.backward_codecs.lucene90.blocktree.Lucene90BlockTreeTermsWriter for the file format.

- Related Packages
  Package
  Description
  org.apache.lucene.backward_codecs.lucene90
  Lucene 9.0 file format.
- Class
  Description
  CompressionAlgorithm
  Compression algorithm used for suffixes of a block of terms.
  FieldReader
  BlockTree's implementation of `Terms`.
  Lucene90BlockTreeTermsReader
  A block-based terms index and dictionary that assigns terms to variable length blocks according to how they share prefixes.
  Stats
  BlockTree statistics for a single field returned by `FieldReader.getStats()`.