Hasura not respecting postgres serial PK

[MattRoelle]

Hi there! I am using Postgres and trying out Hasura.

I have a contact table in my db that looks like this (generated using Prisma):

-- CreateTable
CREATE TABLE "contact" (
    "id" SERIAL NOT NULL,
    "created_at" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
    "first_name" VARCHAR(100) NOT NULL,
    "last_name" VARCHAR(100) NOT NULL,

    CONSTRAINT "contact_pkey" PRIMARY KEY ("id")
);

I am trying to run the following mutation, created using the hasura console explorer.

mutation MyMutation {
  insert_contact(objects: {first_name: "Matt", last_name: "Roelle"}) {    
    returning {
      id
    }
  }
}

In response I get

{
  "errors": [
    {
      "extensions": {
        "path": "$.selectionSet.insert_contact.args.objects",
        "code": "constraint-violation"
      },
      "message": "Uniqueness violation. duplicate key value violates unique constraint \"contact_pkey\""
    }
  ]
}

How do I instruct Hasura to let PG handle the id field?

Thanks!

[MattRoelle]

The following mutation worked, I was using the batch insert mutation I believe.

mutation MyMutation {
  insert_contact_one(object: {first_name: "Matt", last_name: "Roelle"}) {
    id
  }
}