| /* |
| * 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.RelMultipleTrait; |
| import org.apache.calcite.util.mapping.Mappings; |
| |
| import java.util.List; |
| |
| /** |
| * Description of the physical distribution of a relational expression. |
| * |
| * <p>TBD:</p> |
| * <ul> |
| * <li>Can we shorten {@link Type#HASH_DISTRIBUTED} to HASH, etc.</li> |
| * <li>Do we need {@link RelDistributions}.DEFAULT?</li> |
| * <li>{@link RelDistributionTraitDef#convert} |
| * does not create specific physical operators as it does in Drill. Drill |
| * will need to create rules; or we could allow "converters" to be |
| * registered with the planner that are not trait-defs. |
| * </ul> |
| */ |
| public interface RelDistribution extends RelMultipleTrait { |
| /** Returns the type of distribution. */ |
| Type getType(); |
| |
| /** |
| * Returns the ordinals of the key columns. |
| * |
| * <p>Order is important for some types (RANGE); other types (HASH) consider |
| * it unimportant but impose an arbitrary order; other types (BROADCAST, |
| * SINGLETON) never have keys. |
| */ |
| List<Integer> getKeys(); |
| |
| /** |
| * Applies mapping to this distribution trait. |
| * |
| * <p>Mapping can change the distribution trait only if it depends on distribution keys. |
| * |
| * <p>For example if relation is HASH distributed by keys [0, 1], after applying |
| * a mapping (3, 2, 1, 0), the relation will have a distribution HASH(2,3) because |
| * distribution keys changed their ordinals. |
| * |
| * <p>If mapping eliminates one of the distribution keys, the {@link Type#ANY} |
| * distribution will be returned. |
| * |
| * <p>If distribution doesn't have keys (BROADCAST or SINGLETON), method will return |
| * the same distribution. |
| * |
| * @param mapping Mapping |
| * @return distribution with mapping applied |
| */ |
| @Override RelDistribution apply(Mappings.TargetMapping mapping); |
| |
| /** Type of distribution. */ |
| enum Type { |
| /** There is only one instance of the stream. It sees all records. */ |
| SINGLETON("single"), |
| |
| /** There are multiple instances of the stream, and each instance contains |
| * records whose keys hash to a particular hash value. Instances are |
| * disjoint; a given record appears on exactly one stream. */ |
| HASH_DISTRIBUTED("hash"), |
| |
| /** There are multiple instances of the stream, and each instance contains |
| * records whose keys fall into a particular range. Instances are disjoint; |
| * a given record appears on exactly one stream. */ |
| RANGE_DISTRIBUTED("range"), |
| |
| /** There are multiple instances of the stream, and each instance contains |
| * randomly chosen records. Instances are disjoint; a given record appears |
| * on exactly one stream. */ |
| RANDOM_DISTRIBUTED("random"), |
| |
| /** There are multiple instances of the stream, and records are assigned |
| * to instances in turn. Instances are disjoint; a given record appears |
| * on exactly one stream. */ |
| ROUND_ROBIN_DISTRIBUTED("rr"), |
| |
| /** There are multiple instances of the stream, and all records appear in |
| * each instance. */ |
| BROADCAST_DISTRIBUTED("broadcast"), |
| |
| /** Not a valid distribution, but indicates that a consumer will accept any |
| * distribution. */ |
| ANY("any"); |
| |
| public final String shortName; |
| |
| Type(String shortName) { |
| this.shortName = shortName; |
| } |
| } |
| } |