An exemplary computer implemented method for processing data in a database management system implemented on a network of two or more nodes is disclosed. The method includes receiving a query referencing first and second user-defined table functions and a table distributed across the two or more nodes. The first user-defined table function is executed on each of the two or more nodes by processing records of the table residing on the respective nodes. A data sample is generated per node as a result of executing the first user-defined table function on each of the two or more nodes. The generated data samples are stored in a selected set of nodes. The second user-defined table function is executed on each of the selected set of nodes by processing records of the data samples residing on the respective nodes of the selected set of nodes to compute a user-defined aggregate.