/*
* 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.FilterNode;
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.SampleNode;
import com.facebook.presto.sql.tree.ComparisonExpression;
import com.facebook.presto.sql.tree.DoubleLiteral;
import com.facebook.presto.sql.tree.Expression;
import com.facebook.presto.sql.tree.FunctionCall;
import com.facebook.presto.sql.tree.QualifiedName;
import com.google.common.collect.ImmutableList;
import java.util.Map;
import static com.google.common.base.Preconditions.checkNotNull;
public class ImplementSampleAsFilter
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(), plan, null);
}
private static class Rewriter
extends PlanNodeRewriter<Void>
{
@Override
public PlanNode rewriteSample(SampleNode node, Void context, PlanRewriter<Void> planRewriter)
{
if (node.getSampleType() == SampleNode.Type.BERNOULLI) {
PlanNode rewrittenSource = planRewriter.rewrite(node.getSource(), context);
ComparisonExpression expression = new ComparisonExpression(
ComparisonExpression.Type.LESS_THAN,
new FunctionCall(QualifiedName.of("rand"), ImmutableList.<Expression>of()),
new DoubleLiteral(Double.toString(node.getSampleRatio())));
return new FilterNode(node.getId(), rewrittenSource, expression);
}
else if (node.getSampleType() == SampleNode.Type.SYSTEM) {
return rewriteNode(node, context, planRewriter);
}
throw new UnsupportedOperationException("not yet implemented");
}
}
}