presto-main/src/main/java/io/prestosql/operator/SetBuilderOperator.java/SetBuilderOperator/processUnfinishedWork
class SetBuilderOperator:    private boolean processUnfinishedWork()
    {
        // Processes the unfinishedWork for this page by adding the data to the hash table. If this page
        // can't be fully consumed (e.g. rehashing fails), the unfinishedWork will be left with non-empty value.
        checkState(unfinishedWork != null, "unfinishedWork is empty");
        boolean done = unfinishedWork.process();
        if (done) {
            unfinishedWork = null;
        }
        // We need to update the memory reservation again since the page builder memory may also be increasing.
        channelSetBuilder.updateMemoryReservation();
        return done;
    }