| /* |
| * 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.calcite.rel; |
| |
| import org.apache.calcite.plan.RelOptPlanner; |
| import org.apache.calcite.plan.RelTraitDef; |
| import org.apache.calcite.plan.RelTraitSet; |
| import org.apache.calcite.rel.core.Sort; |
| import org.apache.calcite.rel.logical.LogicalSort; |
| |
| /** |
| * Definition of the ordering trait. |
| * |
| * <p>Ordering is a physical property (i.e. a trait) because it can be changed |
| * without loss of information. The converter to do this is the |
| * {@link org.apache.calcite.rel.core.Sort} operator. |
| * |
| * <p>Unlike other current traits, a {@link RelNode} can have more than one |
| * value of this trait simultaneously. For example, |
| * <code>LogicalTableScan(table=TIME_BY_DAY)</code> might be sorted by |
| * <code>{the_year, the_month, the_date}</code> and also by |
| * <code>{time_id}</code>. We have to allow a RelNode to belong to more than |
| * one RelSubset (these RelSubsets are always in the same set).</p> |
| */ |
| public class RelCollationTraitDef extends RelTraitDef<RelCollation> { |
| public static final RelCollationTraitDef INSTANCE = |
| new RelCollationTraitDef(); |
| |
| private RelCollationTraitDef() { |
| } |
| |
| public Class<RelCollation> getTraitClass() { |
| return RelCollation.class; |
| } |
| |
| public String getSimpleName() { |
| return "sort"; |
| } |
| |
| @Override public boolean multiple() { |
| return true; |
| } |
| |
| public RelCollation getDefault() { |
| return RelCollations.EMPTY; |
| } |
| |
| public RelNode convert( |
| RelOptPlanner planner, |
| RelNode rel, |
| RelCollation toCollation, |
| boolean allowInfiniteCostConverters) { |
| if (toCollation.getFieldCollations().isEmpty()) { |
| // An empty sort doesn't make sense. |
| return null; |
| } |
| |
| // Create a logical sort, then ask the planner to convert its remaining |
| // traits (e.g. convert it to an EnumerableSortRel if rel is enumerable |
| // convention) |
| final Sort sort = LogicalSort.create(rel, toCollation, null, null); |
| RelNode newRel = planner.register(sort, rel); |
| final RelTraitSet newTraitSet = rel.getTraitSet().replace(toCollation); |
| if (!newRel.getTraitSet().equals(newTraitSet)) { |
| newRel = planner.changeTraits(newRel, newTraitSet); |
| } |
| return newRel; |
| } |
| |
| public boolean canConvert( |
| RelOptPlanner planner, RelCollation fromTrait, RelCollation toTrait) { |
| return false; |
| } |
| |
| @Override public boolean canConvert(RelOptPlanner planner, |
| RelCollation fromTrait, RelCollation toTrait, RelNode fromRel) { |
| // Returns true only if we can convert. In this case, we can only convert |
| // if the fromTrait (the input) has fields that the toTrait wants to sort. |
| for (RelFieldCollation field : toTrait.getFieldCollations()) { |
| int index = field.getFieldIndex(); |
| if (index >= fromRel.getRowType().getFieldCount()) { |
| return false; |
| } |
| } |
| return true; |
| } |
| } |
| |
| // End RelCollationTraitDef.java |