Function eval_query_partitioned 

pub fn eval_query_partitioned(
    rete: &Rete,
    query: &str,
    opts: QueryOpts,
    var: &str,
    keys: &[String],
) -> Result<(QueryOutput, Vec<QueryWarning>), SparqlError>

eval_query_with_warnings for one chunk of a partition_plan: the query restricted to the solutions whose var is one of keys (term tokens as the keys query returned them, e.g. <https://…>), without its top-level OFFSET/LIMIT. The keys are joined in as VALUES on the first required pattern block that binds var, so each one is an index lookup.

The chunks’ rows, taken in the keys’ order, are the query’s rows — except that the caller applies the plan’s OFFSET/LIMIT and, when the plan says dedupe, drops repeated rows.