Feature Request: pg_trgm

[quadrupleslap]

What do you want to do and how do you expect Diesel to support you with that?

I want to use the pg_trgm module, in particular the similarity, % and <-> functions/operators. Diesel should allow the safe construction of queries involving these.

How do you think this can be added to Diesel?

This'd hopefully be added with similarity(text, text) -> real and word_similarity(text, text) -> real functions, and two text expression methods (text <-> text) : real (distance) and (text % text) : bool (is similar to), and maybe the other functions described on https://www.postgresql.org/docs/9.1/static/pgtrgm.html to be comprehensive. It might also be a good idea to introduce another feature gate.

What are possible alternatives?

Dealing with raw queries, but nobody wants that. :P

Are there any disadvantages?

None that I can think of.

[sgrif]

For non-core modules like these, Diesel is designed to be extended by third party crates. I don't think this makes much sense to be in Diesel proper. Functions can be implemented with the sql_function! macro (http://docs.diesel.rs/diesel/macro.sql_function.html). For a proof of concept of how to implement custom operators/types, please see https://github.com/diesel-rs/diesel_full_text_search