Help on error: Vars can be assigned only at root when grouped by Value

MichelDiz · September 25, 2022, 2:06am

What version are you using? I wasn’t able to find that error in the code

Just this one

dgraph-io/dgraph/blob/0c6071b793a5332f68002b3bae61207c4e15b226/query/groupby.go#L356


      
          		for _, grp := range res.group {
          			if len(grp.keys) == 0 {
          				continue
          			}
          			if len(grp.keys) > 1 {
          				return errors.Errorf("Expected one UID for var in groupby but got: %d", len(grp.keys))
          			}
          			uidVal := grp.keys[0].key.Value
          			uid, ok := uidVal.(uint64)
          			if !ok {
          				return errors.Errorf("Vars can be assigned only when grouped by UID attribute")
          			}
          			// grp.aggregates could be empty if schema conversion failed during aggregation
          			if len(grp.aggregates) > 0 {
          				tempMap[uid] = grp.aggregates[len(grp.aggregates)-1].key
          			}
          		}
          		doneVars[chVar] = varValue{
          			Vals: tempMap,
          			path: append(path, pathNode),
          		}

Update.

I have found it

github.com/dgraph-io/dgraph

feat(DQL): @groupby on scalar fields and count duplicate

dgraph-io:master ← dgraph-io:minhaj/groupby

opened 04:19AM - 23 Apr 21 UTC

minhaj-shakeel

+114 -12

This PR extends support for var inside the @groupby query on a scalar predicate …at root. for example the given query now doesn't result to error:- ``` var(func: ... ) @groupby(age) { c as count(uid) } ``` Now the uid variable `c` contains map of uid to count of uids with the same age. Suppose for the data :- ```{ "uid": "0x1", "age": 38 }, { "uid": "0x17", "age": 15 }, { "uid": "0x18", "age": 15 }, { "uid": "0x19", "age": 17 } ``` The following groupby query:- ``` var(func: uid(1, 23, 24, 25)) @groupby(age) { c as count(uid) } me(func: uid(c)) { uid val(c) } ``` returns the result:- ``` "data": { "me": [ { "uid": "0x1", "val(c)": 1 }, { "uid": "0x17", "val(c)": 2 }, { "uid": "0x18", "val(c)": 2 }, { "uid": "0x19", "val(c)": 1 } ] } ``` The behaviour will be the same if there are multiple predicates and some of them are uid predicates. However, it is only supported at root currently. Hence the given query will still return error:- ``` var(func: .....) { friend @groupby(age) { a as count(uid) } } ```  --- This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/dgraph-io/dgraph/7746)

So, this behavior was changed. You need to modify that query manually. The tutorial was made way before that change.

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Help on error: Vars can be assigned only at root when grouped by Value

Update.

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