Parallel execution of SQL statements is made fault-tolerant. Specifically, during parallel query processing, a new row source is created that allows checkpoints to be stored at certain points in the query processing. If a failure occurs, then the query can be restarted from the most recent checkpoint (rather than from the very beginning of the query). The checkpoints are implemented at operation boundaries where rows need to be redistributed among processes. These are natural checkpoint locations because (1) each subsequent operation can proceed from the output of the previous operation, which is stored as a checkpoint, and (2) these operation completions tend to be points in the computation where the query state is minimized, thus minimizing checkpoint storage requirements.