Composite type support.

[eeeebbbbrrrr]

This will replace PR #57 when complete.

Here's an example:

drop type person cascade;
drop table people cascade;
create type person as (name text, age float8);
create function make_person(name text, age float8) returns person strict parallel safe language plrust as $$
    let mut p = PgHeapTuple::new_composite_type("person")?;
    p.set_by_name("name", name)?;
    p.set_by_name("age", age)?;
    Ok(Some(p))
$$;

create function get_person_name(p person) returns text strict parallel safe language plrust as $$
   Ok(p.get_by_name("name")?)
$$;
create function get_person_age(p person) returns float8 strict parallel safe language plrust as $$
   Ok(p.get_by_name("age")?)
$$;
create function get_person_property(p person, prop text) returns text strict parallel safe language plrust as $$
   match prop.to_lowercase().as_str() {
    "age" => {
        let age:Option<f64> = p.get_by_name("age")?;
        Ok(age.map(|v| v.to_string()))
    },
    "name" => {
        Ok(p.get_by_name("name")?)
    },
    _ => panic!("unknown property: `{prop}`")
   }
$$;

create table people (
    id serial8 not null primary key,
    p person
);

insert into people (p) values (make_person('Eric', 46.24));
insert into people (p) values (make_person('Joe', 99.09));
insert into people (p) values (make_person('Dr. Beverly Crusher of the Starship Enterprise', 32.0));

select *, get_person_name(p), get_person_age(p) from people order by get_person_age(p) desc;

create operator -> (function = get_person_name, rightarg = person);
create operator -# (function = get_person_age, rightarg = person);

select ->p as name, -#p as age from people;

create operator ->> (function = get_person_property, leftarg = person, rightarg = text);
select p->>'name' as name, (p->>'age')::float8 as age from people;

[BradyBonnette]

All of this makes sense! 👍