Lucene90BlockTreeTermsReader
A block-based terms index and dictionary that assigns terms to variable length blocks according to how they share prefixes. The terms index is a prefix trie whose leaves are term blocks. The advantage of this approach is that seekExact is often able to determine a term cannot exist without doing any IO, and intersection with Automata is very fast. Note that this terms dictionary has its own fixed terms index (ie, it does not support a pluggable terms index implementation).
NOTE: this terms dictionary supports min/maxItemsPerBlock during indexing to control how much memory the terms index uses.
The data structure used by this implementation is very similar to a burst trie (http://citeseer.ist.psu.edu/viewdoc/summarydoi=10.1.1.18.3499), but with added logic to break up too-large blocks of all terms sharing a given prefix into smaller ones.
Use org.gnit.lucenekmp.index.CheckIndex with the -verbose option to see summary statistics on the blocks in the dictionary.