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.schemas;
  
  import java.util.Map;
  
  /**
   * A {@link ProjectionConsumer} is a {@link Schema}-aware operation (such as a {@link
   * org.apache.beam.sdk.transforms.DoFn} or {@link org.apache.beam.sdk.transforms.PTransform}) that
   * has a {@link org.apache.beam.sdk.schemas.FieldAccessDescriptor} describing which fields the
   * operation accesses.
   */
  public interface ProjectionConsumer {
    /**
     * Returns a map from input {@link org.apache.beam.sdk.values.TupleTag} id to a {@link
     * org.apache.beam.sdk.schemas.FieldAccessDescriptor} describing which Schema fields {@code this}
     * must access from the corresponding input {@link org.apache.beam.sdk.values.PCollection} to
     * complete successfully. Fields not listed in the {@link
     * org.apache.beam.sdk.schemas.FieldAccessDescriptor} are assumed to be safe to drop from the
     * input. Input {@link org.apache.beam.sdk.values.PCollection}s not found in the keyset are
     * implied to have value {@link FieldAccessDescriptor#withAllFields()}.
     */
    Map<String, FieldAccessDescriptor> consumesProjection();
  }
  