Pg_similarity is an extension to support similarity queries on PostgreSQL. The extension consists of:

* Functions implementing similarity algorithms available in the literature.
These functions can be used as UDFs and are the base for implementing
the similarity operators;
* Operators defined on top of the similarity functions. They use similarity
functions to obtain the similarity threshold and compare its value to a
user-defined threshold to decide if it is a match or not;
* Session variables storing similarity function parameters.