/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.drill.exec.planner.physical.visitor;
import java.util.Collections;
import java.util.List;
import org.apache.drill.exec.planner.physical.Prel;
import org.apache.drill.exec.planner.physical.ProjectPrel;
import org.apache.drill.exec.planner.physical.ScreenPrel;
import org.apache.drill.exec.planner.physical.WriterPrel;
import org.eigenbase.rel.RelNode;
import org.eigenbase.reltype.RelDataType;
import org.eigenbase.rex.RexBuilder;
import org.eigenbase.rex.RexNode;
import com.google.common.collect.Lists;
public class FinalColumnReorderer extends BasePrelVisitor<Prel, Void, RuntimeException>{
static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(FinalColumnReorderer.class);
private static FinalColumnReorderer INSTANCE = new FinalColumnReorderer();
public static Prel addFinalColumnOrdering(Prel prel) {
return prel.accept(INSTANCE, null);
}
@Override
public Prel visitScreen(ScreenPrel prel, Void value) throws RuntimeException {
Prel newChild = ((Prel) prel.getChild()).accept(this, value);
return prel.copy(prel.getTraitSet(), Collections.singletonList( (RelNode) addTrivialOrderedProjectPrel( newChild )));
}
private Prel addTrivialOrderedProjectPrel(Prel prel) {
if ( !prel.needsFinalColumnReordering()) {
return prel;
}
RelDataType t = prel.getRowType();
RexBuilder b = prel.getCluster().getRexBuilder();
List<RexNode> projections = Lists.newArrayList();
int projectCount = t.getFieldList().size();
// no point in reordering if we only have one column
if (projectCount < 2) {
return prel;
}
for (int i =0; i < projectCount; i++) {
projections.add(b.makeInputRef(prel, i));
}
return new ProjectPrel(prel.getCluster(), prel.getTraitSet(), prel, projections, prel.getRowType());
}
@Override
public Prel visitWriter(WriterPrel prel, Void value) throws RuntimeException {
Prel newChild = ((Prel) prel.getChild()).accept(this, null);
return prel.copy(prel.getTraitSet(), Collections.singletonList( (RelNode) addTrivialOrderedProjectPrel( newChild )));
}
@Override
public Prel visitPrel(Prel prel, Void value) throws RuntimeException {
List<RelNode> children = Lists.newArrayList();
boolean changed = false;
for (Prel p : prel) {
Prel newP = p.accept(this, null);
if (newP != p) {
changed = true;
}
children.add(newP);
}
if (changed) {
return (Prel) prel.copy(prel.getTraitSet(), children);
} else {
return prel;
}
}
}