contrib/format-access/src/main/java/org/apache/drill/exec/store/msaccess/MSAccessFormatPlugin.java

/*
 * 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.drill.exec.store.msaccess;

import com.google.common.io.Files;
import org.apache.drill.common.config.DrillConfig;
import org.apache.drill.common.logical.StoragePluginConfig;
import org.apache.drill.common.types.TypeProtos;
import org.apache.drill.common.types.Types;
import org.apache.drill.exec.ExecConstants;
import org.apache.drill.exec.physical.impl.scan.v3.file.FileReaderFactory;
import org.apache.drill.exec.physical.impl.scan.v3.file.FileScanLifecycleBuilder;
import org.apache.drill.exec.physical.impl.scan.v3.file.FileSchemaNegotiator;
import org.apache.drill.exec.physical.impl.scan.v3.ManagedReader;
import org.apache.drill.exec.server.DrillbitContext;
import org.apache.drill.exec.store.dfs.easy.EasyFormatPlugin;
import org.apache.drill.exec.store.dfs.easy.EasySubScan;
import org.apache.hadoop.conf.Configuration;

import java.io.File;


public class MSAccessFormatPlugin extends EasyFormatPlugin<MSAccessFormatConfig> {

  protected static final String DEFAULT_NAME = "msaccess";
  private final DrillbitContext context;

  private static class MSAccessReaderFactory extends FileReaderFactory {

    private final File tempDir;
    private final MSAccessFormatConfig config;
    public MSAccessReaderFactory(File tempDir, MSAccessFormatConfig config) {
      this.tempDir = tempDir;
      this.config = config;
    }

    @Override
    public ManagedReader newReader(FileSchemaNegotiator negotiator) {
      return new MSAccessBatchReader(negotiator, tempDir, config);
    }
  }

  public MSAccessFormatPlugin(String name, DrillbitContext context,
                         Configuration fsConf, StoragePluginConfig storageConfig,
                         MSAccessFormatConfig formatConfig) {
    super(name, easyConfig(fsConf, formatConfig), context, storageConfig, formatConfig);
    this.context = context;
  }

  private static EasyFormatConfig easyConfig(Configuration fsConf, MSAccessFormatConfig pluginConfig) {
    return EasyFormatConfig.builder()
        .readable(true)
        .writable(false)
        .blockSplittable(false)
        .blockSplittable(false)
        .compressible(true)
        .supportsProjectPushdown(true)
        .extensions(pluginConfig.getExtensions())
        .fsConf(fsConf)
        .defaultName(DEFAULT_NAME)
        .scanVersion(ScanFrameworkVersion.EVF_V2)
        .supportsLimitPushdown(true)
        .build();
  }

  @Override
  protected void configureScan(FileScanLifecycleBuilder builder, EasySubScan scan) {
    builder.nullType(Types.optional(TypeProtos.MinorType.VARCHAR));
    builder.readerFactory(new MSAccessReaderFactory(getTmpDir(), formatConfig));
  }

  /**
   * First tries to get drill temporary directory value from config ${drill.tmp-dir},
   * then checks environmental variable $DRILL_TMP_DIR.
   * If value is still missing, generates directory using {@link Files#createTempDir()}.
   *
   * @return drill temporary directory path
   */
  protected File getTmpDir() {
    DrillConfig config = context.getConfig();
    String drillTempDir;
    if (config.hasPath(ExecConstants.DRILL_TMP_DIR)) {
      drillTempDir = config.getString(ExecConstants.DRILL_TMP_DIR);
    } else {
      drillTempDir = System.getenv("DRILL_TMP_DIR");
    }

    if (drillTempDir == null) {
      return Files.createTempDir();
    }
    return new File(drillTempDir);
  }
}