Parameterized cascade fail on 20.11.1

Users Dgraph
1

When issuing the following query on 20.11.1:

{
  q(func:type(Tenant)) @cascade(fields:["app.cn"]) {
    ~app.tnnt @filter(eq(app.cn, "appName")) {
    	app.cn
  	}
  }
}

I get:

{
  "errors": [
    {
      "message": "line 2 column 38: Unexpected item while parsing: :",
      "extensions": {
        "code": "ErrorInvalidRequest"
      }
    }
  ],
  "data": null
}

It work as expected without the parameterized part (just @cascade)
Running docker dgraph/dgraph:v20.11.1

2

Hi @mbn18,

Thanks for reporting this, let me try it out and see

Best,

3

Hey @mbn18

You are using a GraphQL syntax in DQL, therefore you have a syntax error.

The correct query should look like this:

{
  q(func:type(Tenant)) @cascade(app.cn) {
    ~app.tnnt @filter(eq(app.cn, "appName")) {
    	app.cn
  	}
  }
}

In DQL @cascade is queried like this: @cascade(pred1, pred2, ...)

Give it a try and let us know,

Best,

4

Thank Omar, it works.

Please note that the DQL section in the docs missing this version.

Please compare the GraphQL section to the DQL one

Best

5

Thanks Miki, will address this

Best,

1 Like
6

Hi Omar,

Seems like this is not working. the @cascade(predicate) does not raise error but also does not effect the query by filtering out data if the predicate is missing.

Tested with both 20.11.2 and 20.11.1

Sample query:

{
  q(func:type(App)) @cascade(tnnt.cn) {
    app.cn
    app.tnnt @filter(eq(tnnt.cn, "xyz")) {
      tnnt.cn
    }
  }
}

This works:

{
  q(func:type(App)) @cascade {
    app.cn
    app.tnnt @filter(eq(tnnt.cn, "xyz")) {
      tnnt.cn
    }
  }
}
7

Hi @mbn18,

The parameterized cascade works on levels (e.g. on the root function or on lower levels). You need to specify @cascade(param) on the exact level you want it to be applied.

What if you try changing your query to the following one?

{
  q(func:type(App))  {
    app.cn
    app.tnnt @cascade(tnnt.cn) @filter(eq(tnnt.cn, "xyz")) {
      tnnt.cn
    }
  }
}

For further information about parametrized cascade, you can have a look at this post here

Best,

8

Sorry @omar,

It didn’t worked.

Nor in our more complex query when tried on the root level, 2nd level and etc. Tried @cascade(meas.id) on all levels.

Notice that in this query only one of tagv.txt / tagv.int / tagv.float exist. so general cascade will eliminate all records.
And I need to eliminate all app.tags that are not connected to meas.id at the end.

app(func:uid(app_res_uid)) {
  id: app.id
  cn: app.cn
  tags: app.tags {
    cn: tag.cn
    val: ~tagv.tag {
      s: tagv.txt
      i: tagv.int
      f: tagv.float
      ~measureTags  @filter(uid(m_res_uid)) {
        meas.id
      }
    }
  }
}

``
9

I think, what you are trying to achieve with this is: Remove all Apps which are not connected to tnnt.cn. And if you apply @cascade for tnnt.cn at root level, it won’t have any effect as tnnt.cn isn’t a root level predicate.
So, maybe you are looking for this:

{
  q(func:type(App)) @cascade(app.tnnt) {
    app.cn
    app.tnnt @filter(eq(tnnt.cn, "xyz")) @cascade(tnnt.cn) {
      tnnt.cn
    }
  }
}

i.e., remove all the app.tnnt which don’t have a tnnt.cn and then also remove all App which don’t have an app.tnnt

10

Thanks @abhimanyusinghgaur , this is what I missed.

Hope the cascade docs will be updated soon.
Best

11

@docs could someone please update the docs to clarify the finer details discussed in this thread?

Thanks

12

We’ll follow-up, thanks! I filed a ticket for this.

It looks like what we are looking for is:

1 Like
14

We have updated our @cascade DQL docs:
https://dgraph.io/docs/query-language/cascade-directive/

1 Like