Aggregate Queries at root and child levels have been pushed to master. We will soon be updating related documentation.
Related PRs: Feat(GraphQL): Add aggregate query at root level by vmrajas · Pull Request #6985 · dgraph-io/dgraph · GitHub , Feat(GraphQL): Add Aggregation Queries at Child Level by vmrajas · Pull Request #7022 · dgraph-io/dgraph · GitHub .
Note that Aggregate Queries (min, max, sum, avg) are not going to be part of 20.11 .
Count Queries are going to be part of 20.11