The docs provide examples for using UDFs as custom resolvers using the @resolver directive.
Our cookbook has some examples for how to do some more complex searches.
If you are coming from an SQL background, you might check out this recent topic that describes how to mentally translate filtering (SQL WHERE clauses) into indexes.
@Shingai_Munyuki and others, if you have additional questions on how to implement workarounds for graphql filtering and sorting, I encourage you to create a new help topic. That way it can get the attention it needs while this topic can remain as a discussion about the feature request, including desired use cases, proposals for implementations, etc.
further reading:
- feature request: Sorting in autogenerated GraphQL queries
- feature request: Filtering in autogenerated GraphQL queries