schema_migration.md

Schema Migration: SQL to Data Connect GraphQL

Supabase uses standard PostgreSQL Data Definition Language (DDL). Firebase Data Connect uses a GraphQL schema to generate the underlying PostgreSQL schema.

1. Init Data Connect

Run the following command in your project root to initialize Data Connect:

firebase init dataconnect

• Select your Service ID (e.g., todo-service).
• Select your Cloud SQL instance (or create a new one).
• This will create a dataconnect/ folder with schema/schema.gql.

2. Mapping Types

Map your Supabase SQL types to Data Connect GraphQL types.

Supabase SQL	Data Connect GraphQL	Notes
uuid	UUID	Built-in scalar
text / varchar	String
boolean	Boolean
int	Int
timestamptz	Timestamp
references table(id)	@ref directive	Used for relationships

3. Example Mapping: todos Table

Below is an example of how to map a standard SQL table to Data Connect.

Supabase SQL (Source)

create table todos (
  id uuid primary key default gen_random_uuid(),
  title text not null,
  is_complete boolean default false,
  created_at timestamptz default now(),
  user_id uuid default auth.uid() references auth.users(id)
);

Data Connect Schema (schema.gql) (Target)

In Data Connect, you define Types (@table) which generate the underlying SQL. Note: You don't manage auth.users directly in Data Connect schema usually, but you can reference the uid.

# We define a User type if we want to store extra profile data, 
# or we can just store the uid string in Todo.
# For strict foreign key constraints, usually we map the User.

type User @table {
  id: String! @col(name: "uid") # Map to Firebase Auth UID
  email: String
}

type Todo @table {
  id: UUID! @default(expr: "uuid_generate_v4()")
  title: String!
  isComplete: Boolean! @default(value: false)
  createdAt: Timestamp! @default(expr: "now()")
  # Relationship to User
  user: User! @ref
}

4. Security (RLS vs @auth)

Supabase RLS

create policy "Users can view their own todos" on todos
for select using (auth.uid() = user_id);

Data Connect Auth

Use @auth directives on the generic Table Access or specific Queries. Currently, Data Connect recommends securing access via Connectors (Queries/Mutations) with @auth directives.

# In `dataconnect/connector/queries.gql`

query ListMyTodos @auth(level: USER) {
  # The WHERE clause simulates the RLS "using" clause
  todos(where: { user: { id: { eq_expr: "auth.uid" } } }) {
    id
    title
    isComplete
  }
}

Note: Data Connect security is evolving. Check the latest docs for Schema-level @auth availability.