How to setup @search directive?

Users Dgraph
1 
type Product {
    product
    stores
}

product: String  @search(by: fulltext) . #doesn't work
stores: String .
2

@search is for GraphQL schema while @index is for the DQL schema.

https://dgraph.io/docs/query-language/schema/#adding-or-modifying-schema

3

Buy the way how to have dql schema for interfaces?
Could you please show example of an interface?

4

I can add a little more context later, but there is no such thing as an interface in the DQL schema. But the iidea of an interface can be implemented in DQL with types where nodes are of multiple types and one type is the “interface” while the other is the “implementing type”.

I can convert a small GraphQL interface to DQL if you need me to do so.