Filtering relations performance

Users GraphQL
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1

What I want to do

Let’s imagine that I have a graph with ~200 authors and each author can have multiple related entities (posts, photos,videos, …). These related entities can be ~1M for each author. For example, an author can have 1M posts.

If I want to search for posts for a specific author is the following query efficient?

query {
  queryAuthor(authorID: "0x2") {
    name
    posts(filter: {
      score: {
        gt: 10
      },
      and: {
        completed: true
      }
    }) {
      title
      text
      datePublished
    }
  }
}

Are indexes defined inside posts used? Let’s say that I have an index on score field.
Composite indexes are not supported yet, right? So for example in the above case only the index defined in the score will be used?

2

Hi @Davide_Icardi - welcome to the Dgraph forums!

I think you mean indices in the way traditional RDBMSes use them. Indices in Dgraph are somewhat different. They’re used to support searching (exact, hash, etc).

The performance characteristics of a query in Dgraph is dependent upon the predicates. Because Dgraph “shards”* storage by predicate, this is quite equivalent to having an index on every column in a traditional RDBMS. I didn’t quite cover it, but I think you should read this blog post on how things work under the hood. No code involved.

Footnotes
* “shard” is probably not the right word to use. But basically Dgraph stores data by groups of predicates.