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.meta.provider.parquet;
  
  import java.io.Serializable;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Map;
  import org.apache.avro.Schema;
  import org.apache.avro.Schema.Field;
  import org.apache.avro.generic.GenericRecord;
  import org.apache.beam.sdk.annotations.Internal;
  import org.apache.beam.sdk.extensions.avro.schemas.utils.AvroUtils;
  import org.apache.beam.sdk.extensions.sql.meta.BeamSqlTableFilter;
  import org.apache.beam.sdk.extensions.sql.meta.ProjectSupport;
  import org.apache.beam.sdk.extensions.sql.meta.SchemaBaseBeamTable;
  import org.apache.beam.sdk.extensions.sql.meta.Table;
  import org.apache.beam.sdk.io.FileIO;
  import org.apache.beam.sdk.io.parquet.ParquetIO;
  import org.apache.beam.sdk.io.parquet.ParquetIO.Read;
  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.PCollection.IsBounded;
  import org.apache.beam.sdk.values.POutput;
  import org.apache.beam.sdk.values.Row;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  @Internal
  @SuppressWarnings({"nullness"})
  class ParquetTable extends SchemaBaseBeamTable implements Serializable {
    private static final Logger LOG = LoggerFactory.getLogger(ParquetTable.class);
  
    private final Table table;
  
    ParquetTable(Table table) {
      super(table.getSchema());
      this.table = table;
    }
  
    @Override
    public PCollection<Row> buildIOReader(PBegin begin) {
      final Schema schema = AvroUtils.toAvroSchema(table.getSchema());
      String filePattern = resolveFilePattern(table.getLocation());
      Read read = ParquetIO.read(schema).withBeamSchemas(true).from(filePattern);
      return begin.apply("ParquetIORead", read).apply("ToRows", Convert.toRows());
    }
  
    @Override
    public PCollection<Row> buildIOReader(
        PBegin begin, BeamSqlTableFilter filters, List<String> fieldNames) {
      final Schema schema = AvroUtils.toAvroSchema(table.getSchema());
      String filePattern = resolveFilePattern(table.getLocation());
      Read read = ParquetIO.read(schema).withBeamSchemas(true).from(filePattern);
      if (!fieldNames.isEmpty()) {
        Schema projectionSchema = projectSchema(schema, fieldNames);
        LOG.info("Projecting fields schema: {}", projectionSchema);
        read = read.withProjection(projectionSchema, projectionSchema);
      }
      return begin.apply("ParquetIORead", read).apply("ToRows", Convert.toRows());
    }
  
    /** Returns a copy of the {@link Schema} with only the fieldNames fields. */
    private static Schema projectSchema(Schema schema, List<String> fieldNames) {
      List<Field> selectedFields = new ArrayList<>();
      for (String fieldName : fieldNames) {
        selectedFields.add(deepCopyField(schema.getField(fieldName)));
      }
      return Schema.createRecord(
          schema.getName() + "_projected",
          schema.getDoc(),
          schema.getNamespace(),
          schema.isError(),
          selectedFields);
    }
  
    private static Field deepCopyField(Field field) {
      Schema.Field newField =
          new Schema.Field(
              field.name(), field.schema(), field.doc(), field.defaultVal(), field.order());
      for (Map.Entry<String, Object> kv : field.getObjectProps().entrySet()) {
        newField.addProp(kv.getKey(), kv.getValue());
      }
      if (field.aliases() != null) {
        for (String alias : field.aliases()) {
          newField.addAlias(alias);
        }
      }
      return newField;
    }
  
    @Override
    public POutput buildIOWriter(PCollection<Row> input) {
      final org.apache.avro.Schema schema = AvroUtils.toAvroSchema(input.getSchema());
      return input
          .apply("ToGenericRecords", Convert.to(GenericRecord.class))
          .apply(
              "ParquetIOWrite",
              FileIO.<GenericRecord>write().via(ParquetIO.sink(schema)).to(table.getLocation()));
    }
  
    @Override
    public IsBounded isBounded() {
      return PCollection.IsBounded.BOUNDED;
    }
  
    @Override
    public ProjectSupport supportsProjects() {
      return ProjectSupport.WITH_FIELD_REORDERING;
    }
  
    private String resolveFilePattern(String location) {
      if (location.endsWith("/")) {
        return location + "*";
      }
      return location;
    }
  }
  