Give warning when there are no unique constraints on one-to-one columns

src/errors/SchemaValidationError.ts

@@ -40,6 +40,11 @@ const ormSvCodeMap = {
 		message: 'Column type for one-to-one relation (owned side) must be bigint',
 		explanation: 'The column type for a one-to-one relation (owned side) must be defined as a bigint. Resolve by changing the column type to bigint.',
 	},
+	// 3103 Missing index on owned side does not make sense
+	'ORM-SV-3104': {
+		message: 'No unique constraint or unique index was defined for one-to-one relation',
+		explanation: 'Without the database forcing uniqueness, the one-to-one property might be violated and turn into a many-to-one. Putting a unique constraint or unique index on the column is an effective way to prevent this problem.',
+	},
 
 	// One-to-one inverse relations
 	'ORM-SV-3110': {

src/tools/validateSchema.ts

@@ -70,6 +70,16 @@ export async function validateSchema(entityDefinitions: Record<string, BaseEntit
 			if (table[columnName]['udt_name'] != 'int8') {
 				errors.push(new SchemaValidationError('ORM-SV-3102', { entity: entityName, field: fieldName, table: tableName, column: columnName }));
 			}
+
+			// Make sure there is a unique constraint / index on the column in question
+			const hasUniqueIndex = indexes.some(idx => {
+				return idx.tablename == tableName &&
+					idx.indexdef.split('USING')[1].includes('(' + columnName + ')') &&
+					idx.indexdef.includes('CREATE UNIQUE INDEX');
+			});
+			if (!hasUniqueIndex) {
+				warnings.push(new SchemaValidationError('ORM-SV-3104', { entity: entityName, field: fieldName, table: tableName, column: columnName }));
+			}
 		}
 
 		// One-to-one inverse relations

tests/pg-backend/validateSchema.test.ts

@@ -201,5 +201,39 @@ describe('Postgres: validateSchema', () => {
 		expect(result.valid).toBe(true);
 		expect(result.warnings.map(w => w.code)).not.toContain('ORM-SV-3113');
 	});
+
+	it('give a warning when one-to-one does not have unique constraint or unique index', async () => {
+		const result = await runValidationAgainstSchema(`
+			create table "user" (id bigserial primary key, full_name character varying not null, username character varying not null);
+			create table "todo_item" (id bigserial primary key, created_at timestamptz not null, description character varying not null, author_id bigint not null references "user");
+			alter table "user" add column favorite_todo_id bigint references "todo_item";
+			create index on "user" (favorite_todo_id);
+		`, `drop table if exists "user", "todo_item" cascade;`, entitySchema);
+		expect(result.valid).toBe(true);
+		expect(result.warnings.map(w => w.code)).toContain('ORM-SV-3104');
+	});
+
+	it('not give a warning when one-to-one does have a unique constraint', async () => {
+		const result = await runValidationAgainstSchema(`
+			create table "user" (id bigserial primary key, full_name character varying not null, username character varying not null);
+			create table "todo_item" (id bigserial primary key, created_at timestamptz not null, description character varying not null, author_id bigint not null references "user");
+			alter table "user" add column favorite_todo_id bigint references "todo_item";
+			create index on "user" (favorite_todo_id);
+			alter table "user" add constraint uniq_user_favorite_todo unique (favorite_todo_id);
+		`, `drop table if exists "user", "todo_item" cascade;`, entitySchema);
+		expect(result.valid).toBe(true);
+		expect(result.warnings.map(w => w.code)).not.toContain('ORM-SV-3104');
+	});
+
+	it('not give a warning when one-to-one does have a unique index', async () => {
+		const result = await runValidationAgainstSchema(`
+			create table "user" (id bigserial primary key, full_name character varying not null, username character varying not null);
+			create table "todo_item" (id bigserial primary key, created_at timestamptz not null, description character varying not null, author_id bigint not null references "user");
+			alter table "user" add column favorite_todo_id bigint references "todo_item";
+			create unique index on "user" (favorite_todo_id);
+		`, `drop table if exists "user", "todo_item" cascade;`, entitySchema);
+		expect(result.valid).toBe(true);
+		expect(result.warnings.map(w => w.code)).not.toContain('ORM-SV-3104');
+	});
 
 });