Switching between a non-partitioned hash join and a partitioned hash join based on an amount of available memory

A method implemented by at least one processing device, a processing device, and a computer program product are provided for adjusting hash partitions for a hash join operation. An amount of rows within each of an initial number of hash partitions is determined during assignment of respective rows to respective hash partitions. The initial number of hash partitions is adjusted to a final number of hash partitions based on the amount of rows within each of the initial number of hash partitions and an amount of available memory. The adjusting further includes determining the final number of hash partitions based on the amount of rows within each of the initial number of hash partitions and the amount of available memory, and assigning the rows to the final number of hash partitions. The hash join operation is then performed.