Dgraph Tour
blocksvars
GroupBy
A groupby query aggregates query results given a set of properties on which to group elements. For example, a query containing the block
director.film @groupby(genre) {
a as count(uid)
}
finds nodes reachable along the director.film edge, partitions these into groups based on genre, then counts how many nodes are in each group.
Inside a groupby block, only aggregations are allowed and count can only be applied to uid.
The result is the grouped edges and the value variables for the aggregations.
In this case the value variable is a map from genres to values.
Often, it’s necessary to use groupby with another query to obtain values other than aggregations.