Description

Affected components

• Server

Related Issues

fix #1576

Solution and Design

If returning field contains nested selections then mutation is performed in two steps

1. Mutation is performed with returning columns of any primary key and unique constraints
2. returning fields are queried on rows returned by selecting from table by filtering with column values returned in Step 1.

Since mutation takes two courses based on selecting relations in returning field, it is hard to maintain sequence of prepared arguments (PrepArg) generated while resolving returning field. So, we're using txtConverter instead of prepare to resolve mutation fields.

Steps to test and verify

For typical author-article schema:-
Insert an article along with author and query author along with its articles in returning field. It must return inserted article.

Query:-

mutation {
  insert_article(
    objects: [{
      id: 5
      title: "Article by Author 5"
      content: "Content for Article 5"
      author: {
        data: {
          id: 5
          name: "Author 5"
        }
      }
    }]
  ){
    affected_rows
    returning{
      id
      title
      content
      author{
        id
        name
        articles_aggregate{
          aggregate{count}
        }
        articles{
          id
          title
          content
        }
      }
    }
  }
}

Response:-

{
  "data": {
    "insert_article": {
      "affected_rows": 2,
      "returning": [
        {
          "content": "Content for Article 5",
          "author": {
            "name": "Author 5",
            "articles": [
              {
                "content": "Content for Article 5",
                "id": 5,
                "title": "Article by Author 5"
              }
            ],
            "id": 5,
            "articles_aggregate": {
              "aggregate": {
                "count": 1
              }
            }
          },
          "id": 5,
          "title": "Article by Author 5"
        }
      ]
    }
  }
}

Limitations, known bugs & workarounds

Querying relations in returning field of mutation response and Inserting nested objects are strictly available to tables which has atleast one primary key defined or one unique constraints defined on not null columns