cascading deletes error when deleteMany

[openefit]

Describe the bug
It's ok to delete one sheet :

mutation {
  deleteSheet(where: {
      id: "cjkicttn700si0c004zej2o8e"
  }) {
    id
  }
}

errors when use deleleManySheets

mutation {
  deleteManySheets(where: {
    AND: [
      {
        id: "cjkicttn700si0c004zej2o8e"
      }, {
        id: "cjkid9a0400wg0c00hykowvnd"
      }, {
         id: "cjkid9th700x20c00gixwg7cw"
      }
    ]
  }) {
    count
  }
}

error message:

Error: The change you are trying to make would violate the required relation 'SheetRows' between Row and Sheet
    at BatchedGraphQLClient.<anonymous> (/****/node_modules/http-link-dataloader/src/BatchedGraphQLClient.ts:74:13)
    at step (/****/node_modules/http-link-dataloader/dist/src/BatchedGraphQLClient.js:40:23)
    at Object.next (/****/node_modules/http-link-dataloader/dist/src/BatchedGraphQLClient.js:21:53)
    at fulfilled (/****/node_modules/http-link-dataloader/dist/src/BatchedGraphQLClient.js:12:58)
    at process._tickCallback (internal/process/next_tick.js:68:7)
[GraphQL error]: Message: The change you are trying to make would violate the required relation 'SheetRows' between Row and Sheet, Location: [object Object], Path: deleteManySheets
[Network error]: Error: The change you are trying to make would violate the required relation 'SheetRows' between Row and Sheet

To Reproduce
here is the datamodel.graphql

type Sheet {
  id: ID! @unique
  rows: [Row!]! @relation(name: "SheetRows" onDelete: CASCADE)
}

type Row {
  id: ID! @unique
  belong: Sheet! @relation(name: "SheetRows")
  items: [Item!]! @relation(name: "RowItems", onDelete: CASCADE)
}
type Item {
  id: ID! @unique
  belong: Row! @relation(name: "RowItems")
  value: String
}

Versions (please complete the following information):

• OS: Ubuntu 18.04
• prisma CLI: [ prisma/1.13.6 (linux-x64) node-v10.7.0]
• dependencies

{
  "dependencies": {
    "bcryptjs": "2.4.3",
    "crypto": "^1.0.1",
    "graphql-yoga": "^1.14.12",
    "jsonwebtoken": "8.2.0",
    "prisma-binding": "^2.1.1"
  },
  "devDependencies": {
    "@types/bcryptjs": "2.4.1",
    "dotenv-cli": "1.4.0",
    "graphql-cli": "^2.16.5",
    "nodemon": "1.17.3",
    "npm-run-all": "4.1.2",
    "prisma": "^1.12.0",
    "rimraf": "2.6.2",
    "ts-node": "4.1.0",
    "typescript": "2.8.1"
  }
}

[marktani]

Thanks for bringing this up, @openefit! This is a known limitation. You can track our progress with building cascading deletes for deleteMany here: #1936.