Dgraph GraphQL Tour
Basic
Count
You may have noticed that Dgraph generates an <edgeName>Aggregate edge for
every edge pointing to a list. These aggregate edges, along with aggregate
queries, allow you to count the number of items in a query without the need to
return every node.
These aggregate operations return an aggregate result type generated as
<type>AggregateResult. This type provides a unique set of fields for counting
and finding the minimum, maximum, average, and sum values depending on the types
in the schema.
The example query provided here requests every available field
from PersonAggregateResult to return aggregate results from Alice’s
friends, as follows:
count- count how many friends Alice hasxidMin- find the minimum xid value sorted alphabeticallyxidMax- find the maximum xid value sorted alphabeticallynameMin- find the minimum name value sorted alphabeticallynameMax- find the maximum name value sorted alphabeticallyageMin- find the minimum age of Alice’s friendsageMax- find the maximum age of Alice’s friendsageAvg- find the average age of Alice’s friendsageSum- sum of all of the ages of Alice’s friends
The <field>Avg field only averages the values by the
nodes that have a value set. If you have not altered the data from the
Introduction, Alice has six friends, but only four of them have an age set. The
sum age is 113 and the average age across those four nodes is 28.25.
To introspect into the schema for the available fields on the aggregate edges and queries, try the following:
{
__type(name: "<type>AggregateResult") {
name
fields {
name
}
}
}