What does FHQT or FQA mean?

I was reading this post by Andres Pascal, and I came accross a few new acronyms,

As I understand, you need to search strings by similarity (using levenshtein or any other metric distance). In that case, you can use metric indexes like FHQT or FQA (this is better if you are using a relational database, like postgres). But they are not implemented yet in most DBMS, so you need to program the index. It s not too hard, but you need to understand the base concepts. You can look for “searching in metric spaces” to read about it. If you are in a hurry, you can mail me and maybe I can help you.

What exactly do those two acronyms means?

• Fixed Height Queries Tree (FHQT)

  “Metric-Temporal Access Methods” we can find the first definition, as a somewhat interesting aside, one of the primary authors on that paper is Andres Pascal himself. Nice to know he’s working on PostgreSQL.

• Fixed Queries Array (FQA)

  And in “Fixed Queries Array: A Fast and Economical Data Structure for Proximity Searching” in the title.

A rabbit hole to go down another time…