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.extensions.sql.impl.schema;
  
  import org.apache.beam.sdk.extensions.sql.meta.SchemaBaseBeamTable;
  import org.apache.beam.sdk.schemas.transforms.Convert;
  import org.apache.beam.sdk.values.PBegin;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.POutput;
  import org.apache.beam.sdk.values.Row;
  
  /**
   * {@code BeamPCollectionTable} converts a {@code PCollection<Row>} as a virtual table, then a
   * downstream query can query directly.
   */
  public class BeamPCollectionTable<InputT> extends SchemaBaseBeamTable {
    private transient PCollection<InputT> upstream;
  
    public BeamPCollectionTable(PCollection<InputT> upstream) {
      super(upstream.getSchema());
      if (!upstream.hasSchema()) {
        throw new IllegalArgumentException("SQL can only run over PCollections that have schemas.");
      }
      this.upstream = upstream;
    }
  
    @Override
    public PCollection.IsBounded isBounded() {
      return upstream.isBounded();
    }
  
    @Override
    public PCollection<Row> buildIOReader(PBegin begin) {
      assert begin.getPipeline() == upstream.getPipeline();
      return upstream.apply(Convert.toRows());
    }
  
    @Override
    public POutput buildIOWriter(PCollection<Row> input) {
      throw new IllegalArgumentException("cannot use [BeamPCollectionTable] as target");
    }
  }
  