Function is_incrementable 

pub fn is_incrementable(graphql_type: &GraphQLType) -> bool

Whether a column can be added to.

Everything that can be summed, and money beside them: PostgreSQL adds to an amount the way it adds to a number, and Hasura offers _inc on one. It is not in is_numeric because the aggregates that set answers – stddev, variance and their kin – have no money form, and a schema that offered them would be advertising a call the database refuses.