Support for composite primary keys

[amaster507 (Anthony Master)]

Here is another reason why composite keys like this is close to impossible in Dgraph. This correlates to a very similar question

Is it possible to join/merge two indexes? Merging different indexes of the same kind for general search, but also keeping the single indexes

is it possible to join two indexes, of the same type, together, and search through them with the index capability? else I’ll make a feature request for that one, since it’s a very easy feature to implement (since you just create a new index under the hood, sure you duplicate values, but it is what it is, maybe with more sophisticated algorithms you can speed that up, but that ‘shallow’ solution is already more than enough) // better explained what i mean with joint indexes: e.g you have two d…

In Dgraph there you cannot have an index over two predicates because where would the index live if the predicates were not part of the same group. There is a control to manually move predicates to the same group, but if that is not manually done, then it is possible for the two predicates to be distributed across multiple groups (aka servers).

So logically how would you even implement this feature of a unique index across multiple predicates that may be distributed? This would be like saying, it would be like asking SQL to add a unique key constraint across two tables or even two different databases.