A method for detecting and handling skew and spillover in in-memory hash join operations. To improve the detection of skew and spillover in parallel processing systems, a Poisson distribution of unique hash values to Units of Parallelism (UoPs) is employed to determine the number of rows per UoP and in turn, the potential of spillover at a UoP. Hash join plan options can be selected or adjusted to reduce the likelihood of spillover.