Class PigToSqlAggregateRule

@Enclosing public class PigToSqlAggregateRule extends RelRule<PigToSqlAggregateRule.Config>
Planner rule that converts Pig aggregate UDF calls to built-in SQL aggregates.

This rule is applied for logical relational algebra plan that is the result of Pig translation. In Pig, aggregate calls are separate from grouping where we create a bag of all tuples in each group first then apply the Pig aggregate UDF later. It is inefficient to do that in SQL.