/*
* 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.DeleteNode;
import com.facebook.presto.sql.planner.plan.ExchangeNode;
import com.facebook.presto.sql.planner.plan.PlanNode;
import com.facebook.presto.sql.planner.plan.SimplePlanRewriter;
import com.facebook.presto.sql.planner.plan.TableFinishNode;
import com.facebook.presto.sql.planner.plan.ValuesNode;
import com.facebook.presto.sql.tree.LongLiteral;
import com.google.common.collect.ImmutableList;
import java.util.Map;
import static com.google.common.collect.Iterables.getOnlyElement;
/**
* If the predicate for a delete is optimized to false, the target table scan
* of the delete will be replaced with an empty values node. This type of
* plan cannot be executed and is meaningless anyway, so we replace the
* entire thing with a values node.
*/
@Deprecated
public class EmptyDeleteOptimizer
implements PlanOptimizer
{
@Override
public PlanNode optimize(PlanNode plan, Session session, Map<Symbol, Type> types, SymbolAllocator symbolAllocator, PlanNodeIdAllocator idAllocator)
{
return SimplePlanRewriter.rewriteWith(new Rewriter(), plan, null);
}
private static class Rewriter
extends SimplePlanRewriter<Void>
{
@Override
public PlanNode visitTableFinish(TableFinishNode finish, RewriteContext<Void> context)
{
if (finish.getSource() instanceof ExchangeNode) {
ExchangeNode exchange = (ExchangeNode) finish.getSource();
if (exchange.getSources().size() == 1 && (getOnlyElement(exchange.getSources()) instanceof DeleteNode)) {
DeleteNode delete = (DeleteNode) getOnlyElement(exchange.getSources());
if (delete.getSource() instanceof ValuesNode) {
ValuesNode values = (ValuesNode) delete.getSource();
if (values.getRows().isEmpty()) {
return new ValuesNode(
finish.getId(),
finish.getOutputSymbols(),
ImmutableList.of(ImmutableList.of(new LongLiteral("0"))));
}
}
}
}
return finish;
}
}
}