Error Message: Instance Data is not valid whilst updating a GraphQL schema

Question

I had an issue with updating a graphql schema and got this message (in my case I was updating a FaunaDB schema). I couldn't find reference to this online.

Answer 1

Although this is not the most straightforward or descriptive error message ever conceived it simply means that (in this case) I had created a record which would not fit my new schema. (In my case I had added a required field). Although I had deleted records in the specific collection I had not deleted those which referenced that collection.

Answer 2

I received this error because I had entered a query with the same name as a query automatically created by Fauna (or perhaps created by a previous schema?).

This is the code that caused the error:

type User {
  uid: ID! @unique
}

type Query {
  user(uid: ID!): User
}

The solution was to rename the query:

type Query {
  findUser(uid: ID!): User
}

An alternative possible solution with FaunaDB is to override the schema (not just update the schema). This is applicable if the user() query is still in your schema, unwanted, as a result of prior schema updates.