Pgx using Lwt on Mirage for IO
Published: 11 May 2020
PGX is a pure-OCaml PostgreSQL client library, supporting Async, LWT, or synchronous operations.
This library focuses on correctness and safety, with features like:
It is nearly impossible to try to execute a prepared statement that hasn't been prepared.
Trying to run multiple queries at the same time will work properly (although there's no performance benefit, since we currently don't send queries in parallel).
Lots of automated tests.
Pgx.Valuefor parameters and returned data, encouraging people to use the built-in converters instead of trying to handle everything as a string.
Async and LWT support are built in, no need to write your own IO module.
Mirage OS is supported via Pgx_lwt_mirage
We also provide a relatively high-level interface, like
Pgx_async.execute_pipe, which prepares a statement, executes it with the given parameters, returns an
Async.Pipe.Reader.t (so you can stream results), and unprepares the statement when the query is finished.
Significant portions of the code come from PG'Ocaml.
opam install pgx_async # or pgx_lwt_unix or pgx_unix or pgx_lwt_mirage
See pgx_async/bin/pgx_async_example.ml for a complete example of the high-level functional interface. To translate the example to Lwt, replace
>|=. To translate it to synchronous IO / standard-library-only, use
Pgx_unix and replace both
|>, or just replace
>>| fun () -> with
Pgx_unix, you can replace:
Pgx_async.execute ~params "INSERT INTO ..." >>| fun () ->
Pgx_unix.execute ~params "INSERT INTO ...";