/*
* 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.optimizations;
import com.facebook.presto.Session;
import com.facebook.presto.spi.type.Type;
import com.facebook.presto.sql.planner.PlanNodeIdAllocator;
import com.facebook.presto.sql.planner.Symbol;
import com.facebook.presto.sql.planner.SymbolAllocator;
import com.facebook.presto.sql.planner.plan.ApplyNode;
import com.facebook.presto.sql.planner.plan.PlanNode;
import com.facebook.presto.sql.planner.plan.SimplePlanRewriter;
import java.util.Map;
import static com.facebook.presto.sql.planner.optimizations.ScalarQueryUtil.isScalar;
import static com.facebook.presto.sql.planner.plan.SimplePlanRewriter.rewriteWith;
/**
* Remove resolved ApplyNodes with unreferenced scalar input, e.g: "SELECT (SELECT 1)".
*/
public class RemoveUnreferencedScalarInputApplyNodes
implements PlanOptimizer
{
@Override
public PlanNode optimize(PlanNode plan, Session session, Map<Symbol, Type> types, SymbolAllocator symbolAllocator, PlanNodeIdAllocator idAllocator)
{
return rewriteWith(new Rewriter(), plan, null);
}
private static class Rewriter
extends SimplePlanRewriter<PlanNode>
{
@Override
public PlanNode visitApply(ApplyNode node, RewriteContext<PlanNode> context)
{
if (node.getInput().getOutputSymbols().isEmpty() && isScalar(node.getInput()) && node.isResolvedScalarSubquery()) {
return context.rewrite(node.getSubquery());
}
return context.defaultRewrite(node);
}
}
}