Abstract: In some examples, a database system receives a database query. The database system computes a threshold based on sizes of objects, and invokes a distribution process that accounts for data skew to distribute the objects of the object store to processing engines. The distribution process includes determining whether an assignment of a first object to a given processing engine causes a load of the given processing engine to exceed the threshold. In response to a determination that the load of the given processing engine exceeds the threshold, the distribution process divides the first object into object parts and distribute the object parts among one or more processing engines. In response to a determination that the load of the given processing engine does not exceed the threshold, the distribution process assigns the first object to the given processing engine.

Abstract: A cardinality of a query is estimated by creating a join plan for the query. The join plan is converted to a graph representation. A subtree graph kernel matrix is generated for the graph representation of the join plan. The subtree graph kernel matrix is submitted to a trained model for cardinality prediction which produces a predicted cardinality of the query.