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//
//   http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.impala.catalog;

import java.util.concurrent.TimeUnit;

import org.apache.hadoop.hive.metastore.TableType;
import org.apache.hadoop.hive.metastore.api.NoSuchObjectException;
import org.apache.impala.compat.MetastoreShim;
import org.apache.log4j.Logger;

import com.google.common.base.Stopwatch;

import org.apache.impala.catalog.MetaStoreClientPool.MetaStoreClient;
import org.apache.impala.util.ThreadNameAnnotator;

/**
 * Class that implements the logic for how a table's metadata should be loaded from
 * the Hive Metastore / HDFS / etc.
 */
public class TableLoader {
  private static final Logger LOG = Logger.getLogger(TableLoader.class);

  private final CatalogServiceCatalog catalog_;

  // Lock used to serialize calls to the Hive MetaStore to work around MetaStore
  // concurrency bugs. Currently used to serialize calls to "getTable()" due to
  // HIVE-5457.
  private static final Object metastoreAccessLock_ = new Object();

  public TableLoader(CatalogServiceCatalog catalog) {
    catalog_ = catalog;
  }

  /**
   * Creates the Impala representation of Hive/HBase metadata for one table.
   * Calls load() on the appropriate instance of Table subclass.
   * Returns new instance of Table, If there were any errors loading the table metadata
   * an IncompleteTable will be returned that contains details on the error.
   */
  public Table load(Db db, String tblName, String reason) {
    Stopwatch sw = new Stopwatch().start();
    String fullTblName = db.getName() + "." + tblName;
    String annotation = "Loading metadata for: " + fullTblName + " (" + reason + ")";
    LOG.info(annotation);
    Table table;
    // turn all exceptions into TableLoadingException
    try (ThreadNameAnnotator tna = new ThreadNameAnnotator(annotation);
         MetaStoreClient msClient = catalog_.getMetaStoreClient()) {
      org.apache.hadoop.hive.metastore.api.Table msTbl = null;
      // All calls to getTable() need to be serialized due to HIVE-5457.
      synchronized (metastoreAccessLock_) {
        msTbl = msClient.getHiveClient().getTable(db.getName(), tblName);
      }
      // Check that the Hive TableType is supported
      TableType tableType = TableType.valueOf(msTbl.getTableType());
      if (!MetastoreShim.IMPALA_SUPPORTED_TABLE_TYPES.contains(tableType)) {
        throw new TableLoadingException(String.format(
            "Unsupported table type '%s' for: %s", tableType, fullTblName));
      }

      // Create a table of appropriate type and have it load itself
      table = Table.fromMetastoreTable(db, msTbl);
      if (table == null) {
        throw new TableLoadingException(
            "Unrecognized table type for table: " + fullTblName);
      }
      table.load(false, msClient.getHiveClient(), msTbl, reason);
      table.validate();
    } catch (TableLoadingException e) {
      table = IncompleteTable.createFailedMetadataLoadTable(db, tblName, e);
    } catch (NoSuchObjectException e) {
      TableLoadingException tableDoesNotExist = new TableLoadingException(
          "Table " + fullTblName + " no longer exists in the Hive MetaStore. " +
          "Run 'invalidate metadata " + fullTblName + "' to update the Impala " +
          "catalog.");
      table = IncompleteTable.createFailedMetadataLoadTable(
          db, tblName, tableDoesNotExist);
    } catch (Throwable e) {
      table = IncompleteTable.createFailedMetadataLoadTable(
          db, tblName, new TableLoadingException(
          "Failed to load metadata for table: " + fullTblName + ". Running " +
          "'invalidate metadata " + fullTblName + "' may resolve this problem.", e));
    }
    LOG.info("Loaded metadata for: " + fullTblName + " (" +
        sw.elapsedTime(TimeUnit.MILLISECONDS) + "ms)");
    return table;
  }
}