Possible to insert object with many-to-many relation in one query?

I already have many tag objects defined. I have a tag_to_post many-to-many table defined. A user creates a post, sets the title, body, etc. and tags it with 3 tags.

If I insert the post and make 3 insertions into the tag_to_post table in the same query…it can’t work because the tag_to_post insert mutation requires the primary key (id say) of the new post object.

Is there any way to access the last inserted primary key (like RETURNING id) in the same graphql mutation that inserted it?

The only option I see is abandoning Postgres-generated primary keys (auto inc ids, series, etc) and managing random uuids on the app end.

It could be split into 2 queries but then it loses transactionality.

[rikinsk-zz]

@marionschleifer Reopening this to track the docs enhancements. We should add an example for many-to-many relationship in nested inserts.

[rikinsk-zz]

@msmedes I am not sure I completely understand your use case. But on_conflict seems to be what you are looking for. on_conflict does not cancel a mutation as you mentioned but lets you decide what the action should be based on the update_columns field. In case of nested upserts like our case here, if you pass the update_column field as [<conflict-column>] the insert should go through as expected.

The following is the query I would run to insert a post along with its tags (given tag has a unique field called value)

mutation {
  insert_post(
    objects: [
      {
        title: "new post",
        post_tags: {
          data: [
            {
              tag: {
                data: {
                  value: "tech"
                },
                on_conflict: {
                  constraint: tag_value_key,
                  update_columns: [value]
                }
              }
            },
            {
              tag: {
                data: {
                  value: "blog"
                }
                on_conflict: {
                  constraint: tag_value_key,
                  update_columns: [value]
                }
              }
            }
          ]
        }
      }
    ]
  ) {
    returning {
      id
      title
      post_tags {
        id
        tag {
          id
          value
        }
      }
    }
  }
}

with response

{
  "data": {
    "insert_post": {
      "returning": [
        {
          "id": "f03bdccf-6344-4771-851b-efdd9bc5f4fc",
          "title": "new post",
          "post_tags": [
            {
              "tag": {
                "value": "tech",
                "id": "5e8f15fe-c187-4961-940e-d45206a7ff05"
              },
              "id": "99694d90-245b-4157-9496-a630b563ebd7"
            },
            {
              "tag": {
                "value": "blog",
                "id": "dedd495b-fb2c-4b7f-8989-73b67908352d"
              },
              "id": "fa3d372c-2102-40a2-8892-54bb8cd93e58"
            }
          ]
        }
      ]
    }
  }
}

Hope this clarifies things