/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.facebook.presto.sql.planner.iterative.rule;
import com.facebook.presto.Session;
import com.facebook.presto.sql.planner.PlanNodeIdAllocator;
import com.facebook.presto.sql.planner.SymbolAllocator;
import com.facebook.presto.sql.planner.iterative.Lookup;
import com.facebook.presto.sql.planner.iterative.Rule;
import com.facebook.presto.sql.planner.plan.AggregationNode;
import com.facebook.presto.sql.planner.plan.DistinctLimitNode;
import com.facebook.presto.sql.planner.plan.LimitNode;
import com.facebook.presto.sql.planner.plan.PlanNode;
import java.util.Optional;
public class MergeLimitWithDistinct
implements Rule
{
@Override
public Optional<PlanNode> apply(PlanNode node, Lookup lookup, PlanNodeIdAllocator idAllocator, SymbolAllocator symbolAllocator, Session session)
{
if (!(node instanceof LimitNode)) {
return Optional.empty();
}
LimitNode parent = (LimitNode) node;
PlanNode input = lookup.resolve(parent.getSource());
if (!(input instanceof AggregationNode)) {
return Optional.empty();
}
AggregationNode child = (AggregationNode) input;
if (isDistinct(child)) {
return Optional.empty();
}
return Optional.of(
new DistinctLimitNode(
parent.getId(),
child.getSource(),
parent.getCount(),
false,
child.getHashSymbol()));
}
/**
* Whether this node corresponds to a DISTINCT operation in SQL
*/
private boolean isDistinct(AggregationNode node)
{
return !node.getAggregations().isEmpty() ||
node.getOutputSymbols().size() != node.getGroupingKeys().size() ||
!node.getOutputSymbols().containsAll(node.getGroupingKeys());
}
}