This is intended a small little tool to generate all the intial boiler plate needed to use Opaleye. While it could in some cases be run continously as the database updates, it's not going to be possible in all cases because you might have some custom database values that you want to parse into proper haskell types, thus needing to change the generate boilerplate.
To use, just run it with
opaleye-gen -d postgresql://localhost/your_database -o Database.hs
That will read the specification of your_database from the database and
generate a file named Database.hs with all of the necessary Opaleye types to
start writing queries from.