content: /*
   * 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.adapter.cassandra;
  
  import org.apache.calcite.plan.RelOptCluster;
  import org.apache.calcite.plan.RelOptCost;
  import org.apache.calcite.plan.RelOptPlanner;
  import org.apache.calcite.plan.RelTraitSet;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.RelWriter;
  import org.apache.calcite.rel.SingleRel;
  import org.apache.calcite.rel.metadata.RelMetadataQuery;
  import org.apache.calcite.rex.RexLiteral;
  import org.apache.calcite.rex.RexNode;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.List;
  
  /**
   * Implementation of limits in Cassandra.
   */
  public class CassandraLimit extends SingleRel implements CassandraRel {
    public final @Nullable RexNode offset;
    public final @Nullable RexNode fetch;
  
    public CassandraLimit(RelOptCluster cluster, RelTraitSet traitSet,
        RelNode input, @Nullable RexNode offset, @Nullable RexNode fetch) {
      super(cluster, traitSet, input);
      this.offset = offset;
      this.fetch = fetch;
      assert getConvention() == input.getConvention();
    }
  
    @Override public @Nullable RelOptCost computeSelfCost(RelOptPlanner planner,
        RelMetadataQuery mq) {
      // We do this so we get the limit for free
      return planner.getCostFactory().makeZeroCost();
    }
  
    @Override public CassandraLimit copy(RelTraitSet traitSet, List<RelNode> newInputs) {
      return new CassandraLimit(getCluster(), traitSet, sole(newInputs), offset, fetch);
    }
  
    @Override public void implement(Implementor implementor) {
      implementor.visitChild(0, getInput());
      if (offset != null) {
        implementor.offset = RexLiteral.intValue(offset);
      }
      if (fetch != null) {
        implementor.fetch = RexLiteral.intValue(fetch);
      }
    }
  
    @Override public RelWriter explainTerms(RelWriter pw) {
      super.explainTerms(pw);
      pw.itemIf("offset", offset, offset != null);
      pw.itemIf("fetch", fetch, fetch != null);
      return pw;
    }
  }
  