/*
* 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.sql.analyzer.Session;
import com.facebook.presto.sql.analyzer.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.LimitNode;
import com.facebook.presto.sql.planner.plan.MarkDistinctNode;
import com.facebook.presto.sql.planner.plan.PlanNode;
import com.facebook.presto.sql.planner.plan.PlanNodeRewriter;
import com.facebook.presto.sql.planner.plan.PlanRewriter;
import com.facebook.presto.sql.planner.plan.ProjectNode;
import com.facebook.presto.sql.planner.plan.SemiJoinNode;
import com.facebook.presto.sql.planner.plan.SortNode;
import com.facebook.presto.sql.planner.plan.TopNNode;
import com.facebook.presto.sql.planner.plan.UnionNode;
import com.google.common.base.Preconditions;
import java.util.Map;
import static com.google.common.base.Preconditions.checkNotNull;
public class LimitPushDown
extends PlanOptimizer
{
@Override
public PlanNode optimize(PlanNode plan, Session session, Map<Symbol, Type> types, SymbolAllocator symbolAllocator, PlanNodeIdAllocator idAllocator)
{
checkNotNull(plan, "plan is null");
checkNotNull(session, "session is null");
checkNotNull(types, "types is null");
checkNotNull(symbolAllocator, "symbolAllocator is null");
checkNotNull(idAllocator, "idAllocator is null");
return PlanRewriter.rewriteWith(new Rewriter(idAllocator), plan, Long.MAX_VALUE);
}
private static class Rewriter
extends PlanNodeRewriter<Long>
{
private final PlanNodeIdAllocator idAllocator;
private Rewriter(PlanNodeIdAllocator idAllocator)
{
this.idAllocator = Preconditions.checkNotNull(idAllocator, "idAllocator is null");
}
@Override
public PlanNode rewriteNode(PlanNode node, Long limit, PlanRewriter<Long> planRewriter)
{
PlanNode rewrittenNode = planRewriter.defaultRewrite(node, Long.MAX_VALUE);
if (limit != Long.MAX_VALUE) {
// Drop in a LimitNode b/c we cannot push our limit down any further
rewrittenNode = new LimitNode(idAllocator.getNextId(), rewrittenNode, limit);
}
return rewrittenNode;
}
@Override
public PlanNode rewriteLimit(LimitNode node, Long limit, PlanRewriter<Long> planRewriter)
{
return planRewriter.rewrite(node.getSource(), Math.min(node.getCount(), limit));
}
@Override
public PlanNode rewriteMarkDistinct(MarkDistinctNode node, Long limit, PlanRewriter<Long> planRewriter)
{
return planRewriter.defaultRewrite(node, limit);
}
@Override
public PlanNode rewriteProject(ProjectNode node, Long limit, PlanRewriter<Long> planRewriter)
{
return planRewriter.defaultRewrite(node, limit);
}
@Override
public PlanNode rewriteTopN(TopNNode node, Long limit, PlanRewriter<Long> planRewriter)
{
PlanNode rewrittenSource = planRewriter.rewrite(node.getSource(), Long.MAX_VALUE);
if (limit != Long.MAX_VALUE || rewrittenSource != node.getSource()) {
return new TopNNode(node.getId(), rewrittenSource, Math.min(node.getCount(), limit), node.getOrderBy(), node.getOrderings(), node.isPartial());
}
return node;
}
@Override
public PlanNode rewriteSort(SortNode node, Long limit, PlanRewriter<Long> planRewriter)
{
PlanNode rewrittenSource = planRewriter.rewrite(node.getSource(), Long.MAX_VALUE);
if (limit != Long.MAX_VALUE) {
return new TopNNode(node.getId(), rewrittenSource, limit, node.getOrderBy(), node.getOrderings(), false);
}
else if (rewrittenSource != node.getSource()) {
return new SortNode(node.getId(), rewrittenSource, node.getOrderBy(), node.getOrderings());
}
return node;
}
@Override
public PlanNode rewriteUnion(UnionNode node, Long limit, PlanRewriter<Long> planRewriter)
{
PlanNode output = planRewriter.defaultRewrite(node, limit);
if (limit != Long.MAX_VALUE) {
output = new LimitNode(idAllocator.getNextId(), output, limit);
}
return output;
}
@Override
public PlanNode rewriteSemiJoin(SemiJoinNode node, Long limit, PlanRewriter<Long> planRewriter)
{
PlanNode source = planRewriter.rewrite(node.getSource(), limit);
if (source != node.getSource()) {
return new SemiJoinNode(node.getId(), source, node.getFilteringSource(), node.getSourceJoinSymbol(), node.getFilteringSourceJoinSymbol(), node.getSemiJoinOutput());
}
return node;
}
}
}