Support for PostgreSQL's listen/notify

[zhulik]

Hi!

I've just found that it's impossible to generate code out of raw sql which contain LISTEN or NOTIFY:

notify.sql:

-- Notify
NOTIFY foo, 'bar';

Error: unable to fetch table data: parse query folders: parse folder "./sql": parse file "notify.sql": parse queries: parse query 0: get args and cols: prepare: pq: syntax error at or near "NOTIFY"

For notify there is alternative which works:

SELECT pg_notify($1, $2);

However there is no alternative for LISTEN as there is no special function for it.

Sqlc has added support for LISTEN/NOTIFY some time ago

If you give me a clue where to start from, I can try implementing it myself.

Thanks!

[stephenafamo]

Right now, only SELECT, INSERT, UPDATE and DELETE statements are supported.

To implement a new statement, you'd start from gen/bobgen-psql/driver/parser/parser.go. Although, I assume there may be other limitations because of how the query parsing is expected to work with the rest of Bob.
For example, the parsed queries are expected to be able to be recreated using mods.

[manhrev]

Hi @stephenafamo, I added support for LISTEN and NOTIFY statements in psql dialect (also fixed VALUES statement in parsers).
Note that it only add support for sending messages and registering a subscription for a connection. To receive messages, user must implement this using a specific database driver and the driver connection must be kept open manually for messaging (e.g. pgx's WaitForNotification).

Please review the PR #749, thanks!