presto-main/src/main/java/io/prestosql/sql/planner/iterative/rule/AddExchangesBelowPartialAggregationOverGroupIdRuleSet.java/AddExchangesBelowPartialAggregationOverGroupIdRuleSet/maximalConcurrencyAfterRepartition
class AddExchangesBelowPartialAggregationOverGroupIdRuleSet:        private int maximalConcurrencyAfterRepartition(Context context)
        {
            return getTaskConcurrency(context.getSession()) * taskCountEstimator.estimateHashedTaskCount(context.getSession());
        }