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.rel.stream;
  
  import org.apache.calcite.plan.RelOptCluster;
  import org.apache.calcite.plan.RelTraitSet;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.SingleRel;
  
  /**
   * Relational operator that converts a stream to a relation.
   *
   * <p>Chi is named for the Greek letter &chi; and pronounced 'kai'.
   *
   * <p>Chi is the inverse of {@link Delta}. For any relation {@code R},
   * Chi(Delta(R)) == R.
   */
  public class Chi extends SingleRel {
    protected Chi(RelOptCluster cluster, RelTraitSet traits, RelNode input) {
      super(cluster, traits, input);
    }
  }
  