Unique Indexes on predicates

mrjn · November 17, 2017, 8:19pm

We’ve planned this issue for v0.9:

github.com/dgraph-io/dgraph

Assign single UID to predicate

opened 11:06PM - 22 Sep 17 UTC

closed 03:44AM - 11 Jan 19 UTC

calummoore

kind/feature

As posted on the [community forum](https://discuss.hypermode.com/t/single-uid-assign…ed-to-predicate/1787): It would be useful to be able to assign a `uid` to a predicate directly without adding it to a Posting List. For example, I might have a predicate `teacher`, where it is only ever possible to have one `teacher` at a time. At the moment I would have to do the following to update the predicate, which means 2 round trips and is unnecessarily verbose. ``` mutation { delete { <0x4> teacher * . } } mutation { set { <0x4> teacher <0x9> . } } ``` Ideally, you would want to be able to specify in the schema that that predicate only accepts a single uid. ``` mutation { schema { teacher: uid @unary } } ``` It would also have the added benefit of being able to return an object instead of an array when the unary predicate is being queried, as it would know there could only ever be one node/object.

@pawan is assigned to this.

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Unique Indexes on predicates

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