| /* |
| * 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.runtime.Utilities; |
| |
| import com.google.common.collect.Ordering; |
| |
| import java.util.Comparator; |
| |
| /** |
| * Utilities concerning relational expressions. |
| */ |
| public class RelNodes { |
| /** Comparator that provides an arbitrary but stable ordering to |
| * {@link RelNode}s. */ |
| public static final Comparator<RelNode> COMPARATOR = |
| new RelNodeComparator(); |
| |
| /** Ordering for {@link RelNode}s. */ |
| public static final Ordering<RelNode> ORDERING = Ordering.from(COMPARATOR); |
| |
| private RelNodes() {} |
| |
| /** Compares arrays of {@link RelNode}. */ |
| public static int compareRels(RelNode[] rels0, RelNode[] rels1) { |
| int c = Utilities.compare(rels0.length, rels1.length); |
| if (c != 0) { |
| return c; |
| } |
| for (int i = 0; i < rels0.length; i++) { |
| c = COMPARATOR.compare(rels0[i], rels1[i]); |
| if (c != 0) { |
| return c; |
| } |
| } |
| return 0; |
| } |
| |
| /** Arbitrary stable comparator for {@link RelNode}s. */ |
| private static class RelNodeComparator implements Comparator<RelNode> { |
| @Override public int compare(RelNode o1, RelNode o2) { |
| // Compare on field count first. It is more stable than id (when rules |
| // are added to the set of active rules). |
| final int c = Utilities.compare(o1.getRowType().getFieldCount(), |
| o2.getRowType().getFieldCount()); |
| if (c != 0) { |
| return -c; |
| } |
| return Utilities.compare(o1.getId(), o2.getId()); |
| } |
| } |
| } |