add a `pggen.optional()` directive about pggen HOT 5 OPEN

Hi there, I'm interested but life is a bit crazy (we just had our second kiddo). I like the idea of pggen.optional with maybe some tweaks to naming. Optional args fill a gap in pggen.

sqlc calls this sqlc.narg https://docs.sqlc.dev/en/stable/howto/named_parameters.html

from pggen.

The problem is that inputs types are always assumed to be non-null:

I probably can't change that decision without breaking existing code.

We use sentinel values as a stand-in for null with a few helper functions. This works pretty well with Go's default values. Here's what it looks like:

SELECT
  default_if_empty(pggen.arg('foo'), 'my_default_value')

If Foo is an empty string, it'll trigger the default value. Here's the function definition (overloaded with other types):

CREATE FUNCTION default_if_empty(s text, default_str text) RETURNS text AS $$
SELECT coalesce(nullif(s, ''), default_str)
$$ LANGUAGE sql IMMUTABLE PARALLEL SAFE;

from pggen.

Closing this - I'm gathering there is no interest to accept this

from pggen.

Congratulations on the baby! 🍼

When you have time to circle back around to this, feel free to drop your thoughts and I'm happy to update that PR as needed. :)

Cheers!

from pggen.