feat: constraints through smart comments (view foreign keys, etc)

[benjie]

• relations @foreignKey (col1, col2) references other_table (col3, col4) (fix(jwt): handle bigint / numeric in JWTs #376)
• primary key for nodeID / etc @primaryKey (col1, col2)
• ability to override non-null-ness of columns
• soft links (e.g. allowing a value to reference another table where a row may or may not exist)

Fixes graphile/crystal#376

[itaied246]

Getting this error for view foreign key:

create table post (
  id text primary key
);
comment on table post is E'@name post_table
@omit';

create table offer (
  id serial primary key,
  post_id text references post(id) not null,
);
comment on table offer is E'@name offer_table
@omit';

create view post_view as
  SELECT 
    post.id,
    FROM mydb.post post;
comment on view post_view is E'@name posts
@uniqueKey id';

create view offer_view as
  SELECT
    offer.id,
    offer.post_id

    FROM mydb.offer offer;
comment on view offer_view is E'@name offers
@uniqueKey id
@foreignKey (post_id) references posts';

A fatal error occurred when building the initial schema, so the process will now exit. Error details:

TypeError: Cannot read property 'namespaceId' of undefined

[benjie]

That’s a misleading error 👍

[itaied246]

Continue the previous example:

comment on view offer_view is E'@name offers
@uniqueKey id
@foreignKey (post_id) references post_view (id)';

Throws:

A fatal error occurred when building the initial schema, so the process will now exit. Error details:

Error: No columns specified for 'mydb.post_view' (oid: 119745) and no PK found (@foreignKey (post_id) references post_view(id)).

[benjie]

@itaied246 Thanks for these; I've added tests for them and fixed the missing parenthesis which caused the "No columns specified" error. Note you've used @uniqueKey but for it to work like in PostgreSQL where you can omit columns you must instead use @primaryKey (like you would in PostgreSQL).

[benjie]

This now opens up "soft references" - i.e. if you have to tables:

Clowns:

id	name
1	Marbles
2	Boris
3	Smiley

People:

id	name
7	Alice
8	Boris
9	Caroline

Then you could link them together to find people named after clowns, but the constraint is not enforced by the database:

comment on table people is E'@foreignKey (name) references clowns (name)|@fieldName namedAfterClown|@foreignFieldName peopleSharingName';

{
  allPeople {
    nodes {
      id
      name
      namedAfterClown { id name }
    }
  }
}

{
  allPeople: {
    nodes: [
      { id: 7, name: "Alice", namedAfterClown: null },
      { id: 8, name: "Boris", namedAfterClown: { id: 2, name: "Boris" } },
      { id: 9, name: "Caroline", namedAfterClown: null },
    ]
  }
}

(You may have also noticed that I've allowed you to tag these fake constraints too, using the pipe syntax instead of newlines. This is going to get old fast.)