// Used to clean up any missing noops after all the subplans have been altered.
normalization.add(new RemoveRedundantVariablesRule());
normalization.add(new RemoveUnusedAssignAndAggregateRule());
// Convert to a data source scan operator.
normalization.add(new SetCollectionDataSourceRule());
normalization.add(new IntroduceCollectionRule());
normalization.add(new RemoveUnusedAssignAndAggregateRule());
// Adds child steps to the data source scan.
normalization.add(new ConsolidateUnnestsRule());