Dummy foreign keys changes for every generated migration sql

Bug description

When I run prisma migrate dev to create an apply a new migration for e.g. adding new field, the generated SQL every time contains DROP CONSTRAINT and ADD FOREIGN KEY statements, e.g.:

/*
  Warnings:

  - Added the required column `test` to the `User` table without a default value. This is not possible if the table is not empty.

*/
-- DropForeignKey
ALTER TABLE "_CreatorToProblem" DROP CONSTRAINT "_CreatorToProblem_A_fkey";

-- DropForeignKey
ALTER TABLE "_CreatorToProblem" DROP CONSTRAINT "_CreatorToProblem_B_fkey";

-- AlterTable
ALTER TABLE "User" ADD COLUMN     "test" BOOLEAN NOT NULL;

-- AddForeignKey
ALTER TABLE "_CreatorToProblem" ADD FOREIGN KEY ("A") REFERENCES "Creator"("id") ON DELETE CASCADE ON UPDATE CASCADE;

-- AddForeignKey
ALTER TABLE "_CreatorToProblem" ADD FOREIGN KEY ("B") REFERENCES "Problem"("id") ON DELETE CASCADE ON UPDATE CASCADE;

How to reproduce

1. prisma migrate reset
2. Add a new field to schema
3. prisma migrate dev
4. See the dummy sql statements
5. Add a new field to schema
6. prisma migrate dev
7. See the dummy sql statements again …

Expected behavior

Expect to not emit ghost changes every time.

Prisma information

datasource postgres {
  provider = "postgresql"
  url      = env("DATABASE_URL")
}

type Numeric = Float

generator client {
  provider        = "prisma-client-js"
  binaryTargets   = ["windows", "debian-openssl-1.1.x"]
  output          = "../prisma/generated/client"
  previewFeatures = ["orderByRelation", "nApi", "selectRelationCount", "orderByAggregateGroup", "referentialActions", "filterJson", "namedConstraints", "fullTextSearch"]
}

generator typegraphql {
  provider                 = "node ../src/cli/dev.ts"
  output                   = "../prisma/generated/type-graphql"
  emitDMMF                 = true
  simpleResolvers          = false
  useUncheckedScalarInputs = false
  emitIdAsIDType           = true
}

// Role enum comment
/// Role enum doc
enum Role {
  USER
  ADMIN
}

// User model comment
/// User model doc
/// @@TypeGraphQL.type(name: "MainUser")
model User {
  // User model field comment
  /// User model field doc
  id          Int      @id @default(autoincrement())
  email       String   @unique
  /// renamed field doc
  /// @TypeGraphQL.field(name: "firstName")
  name        String?
  age         Int
  /// @TypeGraphQL.field(name: "accountBalance")
  balance     Numeric
  amount      Float
  /// @TypeGraphQL.field(name: "clientPosts")
  posts       post[]   @relation("posts")
  role        Role
  test        Boolean
  /// @TypeGraphQL.omit(output: true)
  editorPosts post[]   @relation("editorPosts")
  grades      Int[]
  aliases     String[]
}

enum PostKind {
  BLOG
  ADVERT
}

model post {
  uuid      String    @id @default(uuid())
  createdAt DateTime  @default(now())
  updatedAt DateTime  @updatedAt
  published Boolean
  title     String
  /// @TypeGraphQL.omit(output: true)
  subtitle  String
  content   String?
  author    User      @relation(fields: [authorId], references: [id], name: "posts", onDelete: Cascade)
  authorId  Int
  /// @TypeGraphQL.omit(output: true)
  editor    User?     @relation(fields: [editorId], references: [id], name: "editorPosts", onDelete: Cascade)
  /// @TypeGraphQL.omit(output: true)
  editorId  Int?
  kind      PostKind?
  metadata  Json
}

model Category {
  name   String
  slug   String
  number Int

  @@unique([slug, number], name: "categoryCompoundUnique")
}

model Patient {
  firstName String
  lastName  String
  email     String

  @@id([firstName, lastName])
}

model Movie {
  directorFirstName String
  directorLastName  String
  director          Director @relation(fields: [directorFirstName, directorLastName], references: [firstName, lastName], onDelete: Cascade)
  title             String

  @@id([directorFirstName, directorLastName, title], name: "movieCompoundId")
}

model Director {
  firstName String
  lastName  String
  movies    Movie[]

  @@id([firstName, lastName])
}

model Problem {
  id          Int       @id @default(autoincrement())
  problemText String
  likedBy     Creator[]
  creator     Creator?  @relation(name: "creator", fields: [creatorId], references: [id], onDelete: Cascade)
  creatorId   Int?
}

model Creator {
  id       Int       @id @default(autoincrement())
  name     String
  likes    Problem[]
  problems Problem[] @relation("creator")
}

model NativeTypeModel {
  id      Int      @id @default(autoincrement()) @postgres.Integer
  bigInt  BigInt?  @postgres.BigInt
  byteA   Bytes?   @postgres.ByteA
  decimal Decimal? @postgres.Decimal
}

Environment & setup

• OS: Ubuntu 20.04
• Database: PostgreSQL
• Node.js version: v16.4.0

Prisma Version

prisma                : 2.30.0
@prisma/client        : 2.30.0
Current platform      : debian-openssl-1.1.x
Query Engine (Binary) : query-engine 60b19f4a1de4fe95741da371b4c44a92f4d1adcb (at node_modules/@prisma/engines/query-engine-debian-openssl-1.1.x)
Migration Engine      : migration-engine-cli 60b19f4a1de4fe95741da371b4c44a92f4d1adcb (at node_modules/@prisma/engines/migration-engine-debian-openssl-1.1.x)
Introspection Engine  : introspection-core 60b19f4a1de4fe95741da371b4c44a92f4d1adcb (at node_modules/@prisma/engines/introspection-engine-debian-openssl-1.1.x)
Format Binary         : prisma-fmt 60b19f4a1de4fe95741da371b4c44a92f4d1adcb (at node_modules/@prisma/engines/prisma-fmt-debian-openssl-1.1.x)
Default Engines Hash  : 60b19f4a1de4fe95741da371b4c44a92f4d1adcb
Studio                : 0.422.0
Preview Features      : orderByRelation, nApi, selectRelationCount, orderByAggregateGroup, referentialActions, filterJson, namedConstraints, fullTextSearch

[MichalLytek]

• new project
• prisma db pull to create schema from database
• prisma migrate dev to reset database, generate migration and apply it
• in sql for that migration I see on the bottom the statements (only create, no drop):

-- AddForeignKey
ALTER TABLE "_CreatorToProblem" ADD FOREIGN KEY ("A") REFERENCES "Creator"("id") ON DELETE CASCADE ON UPDATE CASCADE;

-- AddForeignKey
ALTER TABLE "_CreatorToProblem" ADD FOREIGN KEY ("B") REFERENCES "Problem"("id") ON DELETE CASCADE ON UPDATE CASCADE;

When I then add new field, I still have dummy changes:

/*
  Warnings:

  - Added the required column `test3` to the `User` table without a default value. This is not possible if the table is not empty.

*/
-- DropForeignKey
ALTER TABLE "_CreatorToProblem" DROP CONSTRAINT "_CreatorToProblem_A_fkey";

-- DropForeignKey
ALTER TABLE "_CreatorToProblem" DROP CONSTRAINT "_CreatorToProblem_B_fkey";

-- AlterTable
ALTER TABLE "User" ADD COLUMN     "test3" BOOLEAN NOT NULL;

-- AddForeignKey
ALTER TABLE "_CreatorToProblem" ADD FOREIGN KEY ("A") REFERENCES "Creator"("id") ON DELETE CASCADE ON UPDATE CASCADE;

-- AddForeignKey
ALTER TABLE "_CreatorToProblem" ADD FOREIGN KEY ("B") REFERENCES "Problem"("id") ON DELETE CASCADE ON UPDATE CASCADE;

[janpio]

Yep, something along those lines: We recently added the namedContraints preview feature flag, which might have unfortunately changed the existing behavior as well unexpectedly. That is right up that ballpark, constraint name, special case for implicit m:n relations tables and so on.

Thanks for the digging!