content: /*
   * Copyright 2020 Alibaba Group Holding Limited.
   *
   * 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.alibaba.graphscope.common.ir.rel;
  
  import org.apache.calcite.plan.GraphOptCluster;
  import org.apache.calcite.plan.RelOptCluster;
  import org.apache.calcite.plan.RelTraitSet;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.RelShuttle;
  import org.apache.calcite.rel.RelWriter;
  import org.apache.calcite.rel.SingleRel;
  import org.apache.calcite.rex.RexNode;
  import org.apache.commons.lang3.ObjectUtils;
  
  import java.util.Collections;
  import java.util.List;
  
  // this class is dedicated to supporting `dedup` operator in Gremlin, which is equivalent to the
  // combination of `group` and `project` in SQL
  public class GraphLogicalDedupBy extends SingleRel {
      private final List<RexNode> dedupByKeys;
  
      protected GraphLogicalDedupBy(
              RelOptCluster cluster, RelTraitSet traits, RelNode input, List<RexNode> dedupByKeys) {
          super(cluster, traits, input);
          this.dedupByKeys =
                  ObjectUtils.requireNonEmpty(
                          dedupByKeys, "there should be at least one key in dedup by");
      }
  
      public static GraphLogicalDedupBy create(
              GraphOptCluster cluster, RelNode input, List<RexNode> dedupByKeys) {
          return new GraphLogicalDedupBy(cluster, RelTraitSet.createEmpty(), input, dedupByKeys);
      }
  
      public List<RexNode> getDedupByKeys() {
          return Collections.unmodifiableList(this.dedupByKeys);
      }
  
      @Override
      public RelWriter explainTerms(RelWriter pw) {
          return super.explainTerms(pw).item("dedupByKeys", dedupByKeys);
      }
  
      @Override
      public RelNode copy(RelTraitSet traitSet, List<RelNode> inputs) {
          return new GraphLogicalDedupBy(
                  this.getCluster(), traitSet, inputs.get(0), this.dedupByKeys);
      }
  
      @Override
      public RelNode accept(RelShuttle shuttle) {
          if (shuttle instanceof GraphShuttle) {
              return ((GraphShuttle) shuttle).visit(this);
          }
          return shuttle.visit(this);
      }
  }
  