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.beam.sdk.nexmark.queries;
  
  import org.apache.beam.sdk.nexmark.model.Event;
  import org.apache.beam.sdk.nexmark.model.KnownSize;
  import org.apache.beam.sdk.transforms.PTransform;
  import org.apache.beam.sdk.values.KV;
  import org.apache.beam.sdk.values.PCollection;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * Base class for 'NEXMark' query transforms.
   *
   * <p>A query transform maps an event stream to some known size element stream.
   *
   * <p>A query transform may request a faked side input to join with ids.
   */
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public abstract class NexmarkQueryTransform<T extends KnownSize>
      extends PTransform<PCollection<Event>, PCollection<T>> {
  
    private transient PCollection<KV<Long, String>> sideInput = null;
  
    protected NexmarkQueryTransform(String name) {
      super(name);
    }
  
    /** Whether this query expects a side input to be populated. Defaults to {@code false}. */
    public boolean needsSideInput() {
      return false;
    }
  
    /**
     * Set the side input for the query.
     *
     * <p>Note that due to the nature of side inputs, this instance of the query is now fixed and can
     * only be safely applied in the pipeline where the side input was created.
     */
    public void setSideInput(PCollection<KV<Long, String>> sideInput) {
      this.sideInput = sideInput;
    }
  
    /** Get the side input, if any. */
    public @Nullable PCollection<KV<Long, String>> getSideInput() {
      return sideInput;
    }
  }
  