Abstract: A relational database system has a non-volatile memory, a volatile memory for temporarily storing a set of data records, and a query processor. The volatile memory has an amount of available space for query processing that is segmented into multiple memory pages. Initially, these memory pages are empty and available in a pool for use by the query processor. The query processor establishes a partition table that defines multiple partitions. The query processor partitions incoming data records into the partitions according to a hashing function and stores the data records in memory pages associated with the partitions. As a new data record placed into a particular partition, the query processor attempts to aggregate the new data record with any like data record that already exists in the particular partition. If no like data record exists, the data record is stored separately on the memory page within the partition.