fe/src/main/java/org/apache/impala/catalog/CatalogServiceCatalog.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.impala.catalog;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.locks.ReentrantReadWriteLock;

import com.google.common.base.Stopwatch;
import org.apache.hadoop.fs.RemoteIterator;
import org.apache.hadoop.hdfs.DistributedFileSystem;
import org.apache.hadoop.hdfs.protocol.CachePoolEntry;
import org.apache.hadoop.hdfs.protocol.CachePoolInfo;
import org.apache.hadoop.hive.metastore.api.CurrentNotificationEventId;
import org.apache.hadoop.hive.metastore.api.Database;
import org.apache.hadoop.hive.metastore.api.NoSuchObjectException;
import org.apache.hadoop.hive.metastore.api.UnknownDBException;
import org.apache.impala.analysis.TableName;
import org.apache.impala.authorization.AuthorizationDelta;
import org.apache.impala.authorization.AuthorizationManager;
import org.apache.impala.authorization.AuthorizationPolicy;
import org.apache.impala.catalog.MetaStoreClientPool.MetaStoreClient;
import org.apache.impala.catalog.events.ExternalEventsProcessor;
import org.apache.impala.catalog.events.MetastoreEventsProcessor;
import org.apache.impala.catalog.events.MetastoreEventsProcessor.EventProcessorStatus;
import org.apache.impala.catalog.events.NoOpEventProcessor;
import org.apache.impala.catalog.events.SelfEventContext;
import org.apache.impala.common.FileSystemUtil;
import org.apache.impala.common.ImpalaException;
import org.apache.impala.common.Pair;
import org.apache.impala.common.Reference;
import org.apache.impala.common.RuntimeEnv;
import org.apache.impala.service.BackendConfig;
import org.apache.impala.service.FeSupport;
import org.apache.impala.thrift.CatalogLookupStatus;
import org.apache.impala.thrift.CatalogServiceConstants;
import org.apache.impala.thrift.TCatalog;
import org.apache.impala.thrift.TCatalogInfoSelector;
import org.apache.impala.thrift.TCatalogObject;
import org.apache.impala.thrift.TCatalogObjectType;
import org.apache.impala.thrift.TCatalogUpdateResult;
import org.apache.impala.thrift.TDatabase;
import org.apache.impala.thrift.TEventProcessorMetrics;
import org.apache.impala.thrift.TEventProcessorMetricsSummaryResponse;
import org.apache.impala.thrift.TFunction;
import org.apache.impala.thrift.TGetCatalogUsageResponse;
import org.apache.impala.thrift.TGetPartialCatalogObjectRequest;
import org.apache.impala.thrift.TGetPartialCatalogObjectResponse;
import org.apache.impala.thrift.TGetPartitionStatsRequest;
import org.apache.impala.thrift.TPartialCatalogInfo;
import org.apache.impala.thrift.TPartitionKeyValue;
import org.apache.impala.thrift.TPartitionStats;
import org.apache.impala.thrift.TPrincipalType;
import org.apache.impala.thrift.TPrivilege;
import org.apache.impala.thrift.TTable;
import org.apache.impala.thrift.TTableName;
import org.apache.impala.thrift.TTableUsage;
import org.apache.impala.thrift.TTableUsageMetrics;
import org.apache.impala.thrift.TUniqueId;
import org.apache.impala.thrift.TUpdateTableUsageRequest;
import org.apache.impala.util.CatalogBlacklistUtils;
import org.apache.impala.util.FunctionUtils;
import org.apache.impala.util.PatternMatcher;
import org.apache.impala.util.TUniqueIdUtil;
import org.apache.impala.util.ThreadNameAnnotator;
import org.apache.thrift.TException;
import org.apache.thrift.TSerializer;
import org.apache.thrift.protocol.TBinaryProtocol;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.codahale.metrics.Timer;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;
import com.google.common.collect.Sets;


/**
 * Specialized Catalog that implements the CatalogService specific Catalog
 * APIs. The CatalogServiceCatalog manages loading of all the catalog metadata
 * and processing of DDL requests. The CatalogServiceCatalog maintains a global
 * "catalog version". The version is incremented and assigned to a CatalogObject whenever
 * it is added/modified/removed from the catalog. This means each CatalogObject will have
 * a unique version and assigned versions are strictly increasing.
 *
 * Periodically, the CatalogServiceCatalog collects a delta of catalog updates (based on a
 * specified catalog version) and constructs a topic update to be sent to the statestore.
 * Each catalog topic update is defined by a range of catalog versions (from, to] and the
 * CatalogServiceCatalog guarantees that every catalog object that has a version in the
 * specified range is included in the catalog topic update. Concurrent DDL requests are
 * allowed while a topic update is in progress. Hence, there is a non-zero probability
 * that frequently modified catalog objects may keep skipping topic updates. That can
 * happen when by the time a topic update thread tries to collect an object update, that
 * object is being modified by another metadata operation, causing its version to surpass
 * the 'to' version of the topic update. To ensure that all catalog updates
 * are eventually included in a catalog topic update, we keep track of the number of times
 * each catalog object has skipped a topic update and if that number exceeds a specified
 * threshold, we add the catalog object to the next topic update even if its version is
 * higher than the 'to' version of the topic update. As a result, the same version of an
 * object might be sent in two subsequent topic updates.
 *
 * The CatalogServiceCatalog maintains two logs:
 * - Delete log. Since deleted objects are removed from the cache, the cache itself is
 *   not useful for tracking deletions. This log is used for populating the list of
 *   deleted objects during a topic update by recording the catalog objects that
 *   have been removed from the catalog. An entry with a new version is added to this log
 *   every time an object is removed (e.g. dropTable). Incrementing an object's version
 *   and adding it to the delete log should be performed atomically. An entry is removed
 *   from this log by the topic update thread when the associated deletion entry is
 *   added to a topic update.
 * - Topic update log. This log records information about the catalog objects that have
 *   been included in a catalog topic update. Only the thread that is processing the
 *   topic update is responsible for adding, updating, and removing entries from the log.
 *   All other operations (e.g. addTable) only read topic update log entries but never
 *   modify them. Each entry includes the number of times a catalog object has
 *   skipped a topic update, which version of the object was last sent in a topic update
 *   and what was the version of that topic update. Entries of the topic update log are
 *   garbage-collected every TOPIC_UPDATE_LOG_GC_FREQUENCY topic updates by the topic
 *   update processing thread to prevent the log from growing indefinitely. Metadata
 *   operations using SYNC_DDL are inspecting this log to identify the catalog topic
 *   version that the issuing impalad must wait for in order to ensure that the effects
 *   of this operation have been broadcast to all the coordinators.
 *
 * Known anomalies with SYNC_DDL:
 *   The time-based cleanup process of the topic update log entries may cause metadata
 *   operations that use SYNC_DDL to hang while waiting for specific topic update log
 *   entries. That could happen if the thread processing the metadata operation stalls
 *   for a long period of time (longer than the time to process
 *   TOPIC_UPDATE_LOG_GC_FREQUENCY topic updates) between the time the operation was
 *   applied in the catalog cache and the time the SYNC_DDL version was checked. To reduce
 *   the probability of such an event, we set the value of the
 *   TOPIC_UPDATE_LOG_GC_FREQUENCY to a large value. Also, to prevent metadata operations
 *   from hanging in that path due to unknown issues (e.g. bugs), operations using
 *   SYNC_DDL are not allowed to wait indefinitely for specific topic log entries and an
 *   exception is thrown if the specified max wait time is exceeded. See
 *   waitForSyncDdlVersion() for more details.
 *
 * Table metadata for IncompleteTables (not fully loaded tables) are loaded in the
 * background by the TableLoadingMgr; tables can be prioritized for loading by calling
 * prioritizeLoad(). Background loading can also be enabled for the catalog, in which
 * case missing tables (tables that are not yet loaded) are submitted to the
 * TableLoadingMgr any table metadata is invalidated and on startup. The metadata of
 * fully loaded tables (e.g. HdfsTable, HBaseTable, etc) are updated in-place and don't
 * trigger a background metadata load through the TableLoadingMgr. Accessing a table
 * that is not yet loaded (via getTable()), will load the table's metadata on-demand,
 * out-of-band of the table loading thread pool.
 *
 * See the class comments in CatalogOpExecutor for a description of the locking protocol
 * that should be employed if both the version lock and table locks need to be held at
 * the same time.
 *
 * TODO: Consider removing on-demand loading and have everything go through the table
 * loading thread pool.
 */
public class CatalogServiceCatalog extends Catalog {
  public static final Logger LOG = LoggerFactory.getLogger(CatalogServiceCatalog.class);

  private static final int INITIAL_META_STORE_CLIENT_POOL_SIZE = 10;
  private static final int MAX_NUM_SKIPPED_TOPIC_UPDATES = 2;
  // Timeout for acquiring a table lock
  // TODO: Make this configurable
  private static final long TBL_LOCK_TIMEOUT_MS = 7200000;
  // Time to sleep before retrying to acquire a table lock
  private static final int TBL_LOCK_RETRY_MS = 10;

  private final TUniqueId catalogServiceId_;

  // Fair lock used to synchronize reads/writes of catalogVersion_. Because this lock
  // protects catalogVersion_, it can be used to perform atomic bulk catalog operations
  // since catalogVersion_ cannot change externally while the lock is being held.
  // In addition to protecting catalogVersion_, it is currently used for the
  // following bulk operations:
  // * Building a delta update to send to the statestore in getCatalogObjects(),
  //   so a snapshot of the catalog can be taken without any version changes.
  // * During a catalog invalidation (call to reset()), which re-reads all dbs and tables
  //   from the metastore.
  // * During renameTable(), because a table must be removed and added to the catalog
  //   atomically (potentially in a different database).
  private final ReentrantReadWriteLock versionLock_ = new ReentrantReadWriteLock(true);

  // Last assigned catalog version. Starts at INITIAL_CATALOG_VERSION and is incremented
  // with each update to the Catalog. Continued across the lifetime of the object.
  // Protected by versionLock_.
  // TODO: Handle overflow of catalogVersion_ and nextTableId_.
  // TODO: The name of this variable is misleading and can be interpreted as a property
  // of the catalog server. Rename into something that indicates its role as a global
  // sequence number assigned to catalog objects.
  private long catalogVersion_ = INITIAL_CATALOG_VERSION;

  // The catalog version when we ran reset() last time. Protected by versionLock_.
  private long lastResetStartVersion_ = INITIAL_CATALOG_VERSION;

  // Manages the scheduling of background table loading.
  private final TableLoadingMgr tableLoadingMgr_;

  private final boolean loadInBackground_;

  // Periodically polls HDFS to get the latest set of known cache pools.
  private final ScheduledExecutorService cachePoolReader_ =
      Executors.newScheduledThreadPool(1);

  // Log of deleted catalog objects.
  private final CatalogDeltaLog deleteLog_;

  // Version of the last topic update returned to the statestore.
  // The version of a topic update is the catalog version of the CATALOG object
  // that is added to it.
  private final AtomicLong lastSentTopicUpdate_ = new AtomicLong(-1);

  // Wait time for a topic update.
  private static final long TOPIC_UPDATE_WAIT_TIMEOUT_MS = 10000;

  private final TopicUpdateLog topicUpdateLog_ = new TopicUpdateLog();

  private final String localLibraryPath_;

  private CatalogdTableInvalidator catalogdTableInvalidator_;

  // Manages the event processing from metastore for issuing invalidates on tables
  private ExternalEventsProcessor metastoreEventProcessor_;

  /**
   * See the gflag definition in be/.../catalog-server.cc for details on these modes.
   */
  private static enum TopicMode {
    FULL,
    MIXED,
    MINIMAL
  };
  final TopicMode topicMode_;

  private final long PARTIAL_FETCH_RPC_QUEUE_TIMEOUT_S = BackendConfig.INSTANCE
      .getCatalogPartialFetchRpcQueueTimeoutS();

  private final int MAX_PARALLEL_PARTIAL_FETCH_RPC_COUNT = BackendConfig.INSTANCE
      .getCatalogMaxParallelPartialFetchRpc();

  // Controls concurrent access to doGetPartialCatalogObject() call. Limits the number
  // of parallel requests to --catalog_max_parallel_partial_fetch_rpc.
  private final Semaphore partialObjectFetchAccess_ =
      new Semaphore(MAX_PARALLEL_PARTIAL_FETCH_RPC_COUNT, /*fair =*/ true);

  private AuthorizationManager authzManager_;

  // Databases that will be skipped in loading.
  private final Set<String> blacklistedDbs_;
  // Tables that will be skipped in loading.
  private final Set<TableName> blacklistedTables_;

  /**
   * Initialize the CatalogServiceCatalog using a given MetastoreClientPool impl.
   *
   * @param loadInBackground    If true, table metadata will be loaded in the background.
   * @param numLoadingThreads   Number of threads used to load table metadata.
   * @param metaStoreClientPool A pool of HMS clients backing this Catalog.
   * @throws ImpalaException
   */
  public CatalogServiceCatalog(boolean loadInBackground, int numLoadingThreads,
      TUniqueId catalogServiceId, String localLibraryPath,
      MetaStoreClientPool metaStoreClientPool)
      throws ImpalaException {
    super(metaStoreClientPool);
    blacklistedDbs_ = CatalogBlacklistUtils.parseBlacklistedDbs(
        BackendConfig.INSTANCE.getBlacklistedDbs(), LOG);
    blacklistedTables_ = CatalogBlacklistUtils.parseBlacklistedTables(
        BackendConfig.INSTANCE.getBlacklistedTables(), LOG);
    catalogServiceId_ = catalogServiceId;
    tableLoadingMgr_ = new TableLoadingMgr(this, numLoadingThreads);
    loadInBackground_ = loadInBackground;
    try {
      // We want only 'true' HDFS filesystems to poll the HDFS cache (i.e not S3,
      // local, etc.)
      if (FileSystemUtil.getDefaultFileSystem() instanceof DistributedFileSystem) {
        cachePoolReader_.scheduleAtFixedRate(
            new CachePoolReader(false), 0, 1, TimeUnit.MINUTES);
      }
    } catch (IOException e) {
      LOG.error("Couldn't identify the default FS. Cache Pool reader will be disabled.");
    }
    localLibraryPath_ = localLibraryPath;
    deleteLog_ = new CatalogDeltaLog();
    topicMode_ = TopicMode.valueOf(
        BackendConfig.INSTANCE.getBackendCfg().catalog_topic_mode.toUpperCase());
    catalogdTableInvalidator_ = CatalogdTableInvalidator.create(this,
        BackendConfig.INSTANCE);
    metastoreEventProcessor_ = getEventsProcessor();
    Preconditions.checkState(PARTIAL_FETCH_RPC_QUEUE_TIMEOUT_S > 0);
    // start polling for metastore events
    metastoreEventProcessor_.start();
  }

  /**
   * Initializes the Catalog using the default MetastoreClientPool impl.
   * @param initialHmsCnxnTimeoutSec Time (in seconds) CatalogServiceCatalog will wait
   * to establish an initial connection to the HMS before giving up.
   */
  public CatalogServiceCatalog(boolean loadInBackground, int numLoadingThreads,
      int initialHmsCnxnTimeoutSec, TUniqueId catalogServiceId, String localLibraryPath)
      throws ImpalaException {
    this(loadInBackground, numLoadingThreads, catalogServiceId, localLibraryPath,
        new MetaStoreClientPool(INITIAL_META_STORE_CLIENT_POOL_SIZE,
            initialHmsCnxnTimeoutSec));
  }

  /**
   * Check whether the database is in blacklist
   */
  public boolean isBlacklistedDb(String dbName) {
    return blacklistedDbs_.contains(dbName);
  }

  /**
   * Check whether the table is in blacklist
   */
  public boolean isBlacklistedTable(TableName table) {
    return blacklistedTables_.contains(table);
  }

  /**
   * Check whether the table is in blacklist
   */
  public boolean isBlacklistedTable(String db, String table) {
    return isBlacklistedTable(new TableName(db, table));
  }

  public void setAuthzManager(AuthorizationManager authzManager) {
    authzManager_ = Preconditions.checkNotNull(authzManager);
  }

  /**
   * Returns a Metastore event processor object if
   * <code>BackendConfig#getHMSPollingIntervalInSeconds</code> returns a non-zero
   *.value of polling interval. Otherwise, returns a no-op events processor. It is
   * important to fetch the current notification event id at the Catalog service
   * initialization time so that event processor starts to sync at the event id
   * corresponding to the catalog start time.
   */
  private ExternalEventsProcessor getEventsProcessor() throws ImpalaException {
    long eventPollingInterval = BackendConfig.INSTANCE.getHMSPollingIntervalInSeconds();
    if (eventPollingInterval <= 0) {
      LOG.info(String
          .format("Metastore event processing is disabled. Event polling interval is %d",
              eventPollingInterval));
      return NoOpEventProcessor.getInstance();
    }
    try (MetaStoreClient metaStoreClient = getMetaStoreClient()) {
      CurrentNotificationEventId currentNotificationId =
          metaStoreClient.getHiveClient().getCurrentNotificationEventId();
      return MetastoreEventsProcessor.getInstance(
          this, currentNotificationId.getEventId(), eventPollingInterval);
    } catch (TException e) {
      LOG.error("Unable to fetch the current notification event id from metastore."
          + "Metastore event processing will be disabled.", e);
      throw new CatalogException(
          "Fatal error while initializing metastore event processor", e);
    }
  }

  @VisibleForTesting
  public ExternalEventsProcessor getMetastoreEventProcessor() {
    return metastoreEventProcessor_;
  }

  public boolean isEventProcessingActive() {
    return metastoreEventProcessor_ instanceof MetastoreEventsProcessor
        && EventProcessorStatus.ACTIVE
        .equals(((MetastoreEventsProcessor) metastoreEventProcessor_).getStatus());
  }

  /**
   * Tries to acquire versionLock_ and the lock of 'tbl' in that order. Returns true if it
   * successfully acquires both within TBL_LOCK_TIMEOUT_MS millisecs; both locks are held
   * when the function returns. Returns false otherwise and no lock is held in this case.
   */
  public boolean tryLockTable(Table tbl) {
    try (ThreadNameAnnotator tna = new ThreadNameAnnotator(
        "Attempting to lock table " + tbl.getFullName())) {
      long begin = System.currentTimeMillis();
      long end;
      do {
        versionLock_.writeLock().lock();
        if (tbl.getLock().tryLock()) {
          if (LOG.isTraceEnabled()) {
            end = System.currentTimeMillis();
            LOG.trace(String.format("Lock for table %s was acquired in %d msec",
                tbl.getFullName(), end - begin));
          }
          return true;
        }
        versionLock_.writeLock().unlock();
        try {
          // Sleep to avoid spinning and allow other operations to make progress.
          Thread.sleep(TBL_LOCK_RETRY_MS);
        } catch (InterruptedException e) {
          // ignore
        }
        end = System.currentTimeMillis();
      } while (end - begin < TBL_LOCK_TIMEOUT_MS);
      return false;
    }
  }

  /**
   * Reads the current set of cache pools from HDFS and updates the catalog.
   * Called periodically by the cachePoolReader_.
   */
  protected class CachePoolReader implements Runnable {
    // If true, existing cache pools will get a new catalog version and, consequently,
    // they will be added to the next topic update, triggering an update in each
    // coordinator's local catalog cache. This is needed for the case of INVALIDATE
    // METADATA where a new catalog version needs to be assigned to every catalog object.
    private final boolean incrementVersions_;
    /**
     * This constructor is needed to create a non-threaded execution of the class.
     */
    public CachePoolReader(boolean incrementVersions) {
      super();
      incrementVersions_ = incrementVersions;
    }

    @Override
    public void run() {
      if (LOG.isTraceEnabled()) LOG.trace("Reloading cache pool names from HDFS");

      // Map of cache pool name to CachePoolInfo. Stored in a map to allow Set operations
      // to be performed on the keys.
      Map<String, CachePoolInfo> currentCachePools = new HashMap<>();
      try {
        DistributedFileSystem dfs = FileSystemUtil.getDistributedFileSystem();
        RemoteIterator<CachePoolEntry> itr = dfs.listCachePools();
        while (itr.hasNext()) {
          CachePoolInfo cachePoolInfo = itr.next().getInfo();
          currentCachePools.put(cachePoolInfo.getPoolName(), cachePoolInfo);
        }
      } catch (Exception e) {
        LOG.error("Error loading cache pools: ", e);
        return;
      }

      versionLock_.writeLock().lock();
      try {
        // Determine what has changed relative to what we have cached.
        Set<String> droppedCachePoolNames = Sets.difference(
            hdfsCachePools_.keySet(), currentCachePools.keySet());
        Set<String> createdCachePoolNames = Sets.difference(
            currentCachePools.keySet(), hdfsCachePools_.keySet());
        Set<String> survivingCachePoolNames = Sets.difference(
            hdfsCachePools_.keySet(), droppedCachePoolNames);
        // Add all new cache pools.
        for (String createdCachePool: createdCachePoolNames) {
          HdfsCachePool cachePool = new HdfsCachePool(
              currentCachePools.get(createdCachePool));
          cachePool.setCatalogVersion(incrementAndGetCatalogVersion());
          hdfsCachePools_.add(cachePool);
        }
        // Remove dropped cache pools.
        for (String cachePoolName: droppedCachePoolNames) {
          HdfsCachePool cachePool = hdfsCachePools_.remove(cachePoolName);
          if (cachePool != null) {
            cachePool.setCatalogVersion(incrementAndGetCatalogVersion());
            TCatalogObject removedObject =
                new TCatalogObject(TCatalogObjectType.HDFS_CACHE_POOL,
                    cachePool.getCatalogVersion());
            removedObject.setCache_pool(cachePool.toThrift());
            deleteLog_.addRemovedObject(removedObject);
          }
        }
        if (incrementVersions_) {
          // Increment the version of existing pools in order to be added to the next
          // topic update.
          for (String survivingCachePoolName: survivingCachePoolNames) {
            HdfsCachePool cachePool = hdfsCachePools_.get(survivingCachePoolName);
            Preconditions.checkNotNull(cachePool);
            cachePool.setCatalogVersion(incrementAndGetCatalogVersion());
          }
        }
      } finally {
        versionLock_.writeLock().unlock();
      }
    }
  }

  public int getPartialFetchRpcQueueLength() {
    return partialObjectFetchAccess_.getQueueLength();
  }

  /**
   * Adds a list of cache directive IDs for the given table name. Asynchronously
   * refreshes the table metadata once all cache directives complete.
   */
  public void watchCacheDirs(List<Long> dirIds, TTableName tblName, String reason) {
    tableLoadingMgr_.watchCacheDirs(dirIds, tblName, reason);
  }

  /**
   * Prioritizes the loading of the given list TCatalogObjects. Currently only support
   * loading Table/View metadata since Db and Function metadata is not loaded lazily.
   */
  public void prioritizeLoad(List<TCatalogObject> objectDescs) {
    for (TCatalogObject catalogObject: objectDescs) {
      Preconditions.checkState(catalogObject.isSetTable());
      TTable table = catalogObject.getTable();
      tableLoadingMgr_.prioritizeLoad(new TTableName(table.getDb_name().toLowerCase(),
          table.getTbl_name().toLowerCase()));
    }
  }

  /**
   * Retrieves TPartitionStats as a map that associates partitions with their
   * statistics. The table partitions are specified in
   * TGetPartitionStatsRequest. If statistics are not available for a partition,
   * a default TPartitionStats is used. Partitions are identified by their partitioning
   * column string values.
   */
  public Map<String, ByteBuffer> getPartitionStats(TGetPartitionStatsRequest request)
      throws CatalogException {
    Preconditions.checkState(!RuntimeEnv.INSTANCE.isTestEnv());
    TTableName tableName = request.table_name;
    LOG.info("Fetching partition statistics for: " + tableName.getDb_name() + "."
        + tableName.getTable_name());
    Table table = getOrLoadTable(tableName.db_name, tableName.table_name,
        "needed to fetch partition stats");

    // Table could be null if it does not exist anymore.
    if (table == null) {
      throw new CatalogException(
          "Requested partition statistics for table that does not exist: "
          + request.table_name);
    }

    // Table could be incomplete, in which case an exception should be thrown.
    if (table instanceof IncompleteTable) {
      throw new CatalogException("No statistics available for incompletely"
          + " loaded table: " + request.table_name, ((IncompleteTable) table).getCause());
    }

    // Table must be a FeFsTable type at this point.
    Preconditions.checkArgument(table instanceof HdfsTable,
        "Partition statistics can only be requested for FS tables, type is: %s",
        table.getClass().getCanonicalName());

    // Table must be loaded.
    Preconditions.checkState(table.isLoaded());

    Map<String, ByteBuffer> stats = new HashMap<>();
    HdfsTable hdfsTable = (HdfsTable) table;
    hdfsTable.getLock().lock();
    try {
      Collection<? extends PrunablePartition> partitions = hdfsTable.getPartitions();
      for (PrunablePartition partition : partitions) {
        Preconditions.checkState(partition instanceof FeFsPartition);
        FeFsPartition fsPartition = (FeFsPartition) partition;
        TPartitionStats partStats = fsPartition.getPartitionStats();
        if (partStats != null) {
          ByteBuffer compressedStats =
              ByteBuffer.wrap(fsPartition.getPartitionStatsCompressed());
          stats.put(FeCatalogUtils.getPartitionName(fsPartition), compressedStats);
        }
      }
    } finally {
      hdfsTable.getLock().unlock();
    }
    LOG.info("Fetched partition statistics for " + stats.size()
        + " partitions on: " + hdfsTable.getFullName());
    return stats;
  }

  /**
   * The context for add*ToCatalogDelta(), called by getCatalogDelta. It contains
   * callback information, version range and collected topics.
   */
  class GetCatalogDeltaContext {
    // The CatalogServer pointer for NativeAddPendingTopicItem() callback.
    long nativeCatalogServerPtr;
    // The from and to version of this delta.
    long fromVersion;
    long toVersion;
    long lastResetStartVersion;
    // The keys of the updated topics.
    Set<String> updatedCatalogObjects;
    TSerializer serializer;

    GetCatalogDeltaContext(long nativeCatalogServerPtr, long fromVersion, long toVersion,
        long lastResetStartVersion)
    {
      this.nativeCatalogServerPtr = nativeCatalogServerPtr;
      this.fromVersion = fromVersion;
      this.toVersion = toVersion;
      this.lastResetStartVersion = lastResetStartVersion;
      updatedCatalogObjects = new HashSet<>();
      serializer = new TSerializer(new TBinaryProtocol.Factory());
    }

    void addCatalogObject(TCatalogObject obj, boolean delete) throws TException {
      String key = Catalog.toCatalogObjectKey(obj);
      if (obj.type != TCatalogObjectType.CATALOG) {
        topicUpdateLog_.add(key,
            new TopicUpdateLog.Entry(0, obj.getCatalog_version(), toVersion));
        if (!delete) updatedCatalogObjects.add(key);
      }
      // TODO: TSerializer.serialize() returns a copy of the internal byte array, which
      // could be elided.
      if (topicMode_ == TopicMode.FULL || topicMode_ == TopicMode.MIXED) {
        String v1Key = CatalogServiceConstants.CATALOG_TOPIC_V1_PREFIX + key;
        byte[] data = serializer.serialize(obj);
        if (!FeSupport.NativeAddPendingTopicItem(nativeCatalogServerPtr, v1Key,
            obj.catalog_version, data, delete)) {
          LOG.error("NativeAddPendingTopicItem failed in BE. key=" + v1Key + ", delete="
              + delete + ", data_size=" + data.length);
        }
      }

      if (topicMode_ == TopicMode.MINIMAL || topicMode_ == TopicMode.MIXED) {
        // Serialize a minimal version of the object that can be used by impalads
        // that are running in 'local-catalog' mode. This is used by those impalads
        // to invalidate their local cache.
        TCatalogObject minimalObject = getMinimalObjectForV2(obj);
        if (minimalObject != null) {
          byte[] data = serializer.serialize(minimalObject);
          String v2Key = CatalogServiceConstants.CATALOG_TOPIC_V2_PREFIX + key;
          if (!FeSupport.NativeAddPendingTopicItem(nativeCatalogServerPtr, v2Key,
              obj.catalog_version, data, delete)) {
            LOG.error("NativeAddPendingTopicItem failed in BE. key=" + v2Key + ", delete="
                + delete + ", data_size=" + data.length);
          }
        }
      }
    }

    private TCatalogObject getMinimalObjectForV2(TCatalogObject obj) {
      Preconditions.checkState(topicMode_ == TopicMode.MINIMAL ||
          topicMode_ == TopicMode.MIXED);
      TCatalogObject min = new TCatalogObject(obj.type, obj.catalog_version);
      switch (obj.type) {
      case DATABASE:
        min.setDb(new TDatabase(obj.db.db_name));
        break;
      case TABLE:
      case VIEW:
        min.setTable(new TTable(obj.table.db_name, obj.table.tbl_name));
        break;
      case CATALOG:
        // Sending the top-level catalog version is important for implementing SYNC_DDL.
        // This also allows impalads to detect a catalogd restart and invalidate the
        // whole catalog.
        // TODO(todd) ensure that the impalad does this invalidation as required.
        return obj;
      case PRIVILEGE:
      case PRINCIPAL:
      case AUTHZ_CACHE_INVALIDATION:
        // The caching of this data on the impalad side is somewhat complex
        // and this code is also under some churn at the moment. So, we'll just publish
        // the full information rather than doing fetch-on-demand.
        return obj;
      case FUNCTION:
        TFunction fnObject = new TFunction(obj.fn.getName());
        // IMPALA-8486: add the hdfs location so coordinators can mark their libCache
        // entry for this function to be stale.
        if (obj.fn.hdfs_location != null) fnObject.setHdfs_location(obj.fn.hdfs_location);
        min.setFn(fnObject);
        break;
      case DATA_SOURCE:
      case HDFS_CACHE_POOL:
        // These are currently not cached by v2 impalad.
        // TODO(todd): handle these items.
        return null;
      default:
        throw new AssertionError("Unexpected catalog object type: " + obj.type);
      }
      return min;
    }

    public boolean versionNotInRange(long version) {
      return version <= fromVersion || version > toVersion;
    }
  }

  /**
   * Identifies the catalog objects that were added/modified/deleted in the catalog with
   * versions > 'fromVersion'. It operates on a snaphsot of the catalog without holding
   * the catalog lock which means that other concurrent metadata operations can still make
   * progress while the catalog delta is computed. An entry in the topic update log is
   * added for every catalog object that is included in the catalog delta. The log is
   * examined by operations using SYNC_DDL to determine which topic update covers the
   * result set of metadata operation. Once the catalog delta is computed, the entries in
   * the delete log with versions less than 'fromVersion' are garbage collected.
   * The catalog delta is passed to the backend by calling NativeAddPendingTopicItem().
   */
  public long getCatalogDelta(long nativeCatalogServerPtr, long fromVersion) throws
      TException {
    GetCatalogDeltaContext ctx;
    // Get lock to read catalogVersion_ and lastResetStartVersion_
    versionLock_.readLock().lock();
    try {
      ctx = new GetCatalogDeltaContext(nativeCatalogServerPtr, fromVersion,
          catalogVersion_, lastResetStartVersion_);
    } finally {
      versionLock_.readLock().unlock();
    }
    for (Db db: getAllDbs()) {
      addDatabaseToCatalogDelta(db, ctx);
    }
    for (DataSource dataSource: getAllDataSources()) {
      addDataSourceToCatalogDelta(dataSource, ctx);
    }
    for (HdfsCachePool cachePool: getAllHdfsCachePools()) {
      addHdfsCachePoolToCatalogDelta(cachePool, ctx);
    }
    for (Role role: getAllRoles()) {
      addPrincipalToCatalogDelta(role, ctx);
    }
    for (User user: getAllUsers()) {
      addPrincipalToCatalogDelta(user, ctx);
    }
    for (AuthzCacheInvalidation authzCacheInvalidation: getAllAuthzCacheInvalidation()) {
      addAuthzCacheInvalidationToCatalogDelta(authzCacheInvalidation, ctx);
    }
    // Identify the catalog objects that were removed from the catalog for which their
    // versions are in range ('ctx.fromVersion', 'ctx.toVersion']. We need to make sure
    // that we don't include "deleted" objects that were re-added to the catalog.
    for (TCatalogObject removedObject:
        getDeletedObjects(ctx.fromVersion, ctx.toVersion)) {
      if (!ctx.updatedCatalogObjects.contains(
          Catalog.toCatalogObjectKey(removedObject))) {
        ctx.addCatalogObject(removedObject, true);
      }
    }
    // Each topic update should contain a single "TCatalog" object which is used to
    // pass overall state on the catalog, such as the current version and the
    // catalog service id. By setting the catalog version to the latest catalog
    // version at this point, it ensures impalads will always bump their versions,
    // even in the case where an object has been dropped. Also pass the catalog version
    // when we reset the entire catalog last time. So coordinators in local catalog mode
    // can safely forward their min catalog version.
    TCatalogObject catalog =
        new TCatalogObject(TCatalogObjectType.CATALOG, ctx.toVersion);
    catalog.setCatalog(new TCatalog(catalogServiceId_, ctx.lastResetStartVersion));
    ctx.addCatalogObject(catalog, false);
    // Garbage collect the delete and topic update log.
    deleteLog_.garbageCollect(ctx.toVersion);
    topicUpdateLog_.garbageCollectUpdateLogEntries(ctx.toVersion);
    lastSentTopicUpdate_.set(ctx.toVersion);
    // Notify any operation that is waiting on the next topic update.
    synchronized (topicUpdateLog_) {
      topicUpdateLog_.notifyAll();
    }
    return ctx.toVersion;
  }

  /**
   * Gets the list of versions for in-flight events for the given table. Applicable
   * only when external event processing is enabled.
   * @param dbName database name
   * @param tblName table name
   * @return List of previous version numbers for in-flight events on this table.
   * If table is not laoded returns a empty list. If event processing is disabled,
   * returns a empty list
   */
  public List<Long> getInFlightVersionsForEvents(String dbName, String tblName)
      throws DatabaseNotFoundException, TableNotFoundException {
    Preconditions.checkState(isEventProcessingActive(),
        "Event processing should be enabled before calling this method");
    List<Long> result = Collections.EMPTY_LIST;
    versionLock_.readLock().lock();
    try {
      Db db = getDb(dbName);
      if (db == null) {
        throw new DatabaseNotFoundException(
            String.format("Database %s not found", dbName));
      }
      if (tblName == null) {
        return db.getVersionsForInflightEvents();
      }
      Table tbl = getTable(dbName, tblName);
      if (tbl == null) {
        throw new TableNotFoundException(
            String.format("Table %s not found", new TableName(dbName, tblName)));
      }
      if (tbl instanceof IncompleteTable) return result;
      return tbl.getVersionsForInflightEvents();
    } finally {
      versionLock_.readLock().unlock();
    }
  }

  /**
   * Evaluates if the information from an event (serviceId and versionNumber) matches to
   * the catalog object. If there is match, the in-flight version for that object is
   * removed and method returns true. If it does not match, returns false
   * @param ctx self context which provides all the information needed to
   * evaluate if this is a self-event or not
   * @return true if given event information evaluates to a self-event, false otherwise
   */
  public boolean evaluateSelfEvent(SelfEventContext ctx)
      throws CatalogException {
    Preconditions.checkState(isEventProcessingActive(),
        "Event processing should be enabled when calling this method");
    long versionNumber = ctx.getVersionNumberFromEvent();
    String serviceIdFromEvent = ctx.getServiceIdFromEvent();
    // no version info or service id in the event
    if (versionNumber == -1 || serviceIdFromEvent.isEmpty()) return false;
    // if the service id from event doesn't match with our service id this is not a
    // self-event
    if (!getCatalogServiceId().equals(serviceIdFromEvent)) return false;
    Db db = getDb(ctx.getDbName());
    if (db == null) {
      throw new DatabaseNotFoundException("Database " + ctx.getDbName() + " not found");
    }
    // if the given tblName is null we look db's in-flight events
    if (ctx.getTblName() == null) {
      return db.removeFromVersionsForInflightEvents(versionNumber);
    }
    Table tbl = getTable(ctx.getDbName(), ctx.getTblName());
    if (tbl == null) {
      throw new TableNotFoundException(
          String.format("Table %s.%s not found", ctx.getDbName(), ctx.getTblName()));
    }
    // we should acquire the table lock so that we wait for any other updates
    // happening to this table at the same time
    if (!tryLockTable(tbl)) {
      throw new CatalogException(String.format("Error during self-event evaluation "
          + "for table %s due to lock contention", tbl.getFullName()));
    }
    versionLock_.writeLock().unlock();
    try {
      List<List<TPartitionKeyValue>> partitionKeyValues = ctx.getPartitionKeyValues();
      // if the partitionKeyValues is null, we look for tbl's in-flight events
      if (partitionKeyValues == null) {
        return tbl.removeFromVersionsForInflightEvents(versionNumber);
      }
      if (tbl instanceof HdfsTable) {
        List<String> failingPartitions = new ArrayList<>();
        for (List<TPartitionKeyValue> partitionKeyValue : partitionKeyValues) {
          HdfsPartition hdfsPartition =
              ((HdfsTable) tbl).getPartitionFromThriftPartitionSpec(partitionKeyValue);
          if (hdfsPartition == null || !hdfsPartition
              .removeFromVersionsForInflightEvents(versionNumber)) {
            // even if this is an error condition we should not bail out early since we
            // should clean up the self-event state on the rest of the partitions
            String partName = HdfsTable.constructPartitionName(partitionKeyValue);
            if (hdfsPartition == null) {
              LOG.warn(String.format("Partition %s not found during self-event "
                + "evaluation for the table %s", partName, tbl.getFullName()));
            }
            failingPartitions.add(partName);
          }
        }
        return failingPartitions.isEmpty();
      }
    } finally {
      tbl.getLock().unlock();
    }
    return false;
  }

  /**
   * Adds a given version number from the catalog table's list of versions for in-flight
   * events. Applicable only when external event processing is enabled.
   *
   * @param tbl Catalog table
   * @param versionNumber version number to be added
   */
  public void addVersionsForInflightEvents(Table tbl, long versionNumber) {
    if (!isEventProcessingActive()) return;
    // we generally don't take locks on Incomplete tables since they are atomically
    // replaced during load
    Preconditions.checkState(
        tbl instanceof IncompleteTable || tbl.getLock().isHeldByCurrentThread());
    tbl.addToVersionsForInflightEvents(versionNumber);
  }

  /**
   * Adds a given version number from the catalog database's list of versions for
   * in-flight events. Applicable only when external event processing is enabled.
   *
   * @param db Catalog database
   * @param versionNumber version number to be added
   */
  public void addVersionsForInflightEvents(Db db, long versionNumber) {
    if (!isEventProcessingActive()) return;
    db.addToVersionsForInflightEvents(versionNumber);
  }

  /**
   * Get a snapshot view of all the catalog objects that were deleted between versions
   * ('fromVersion', 'toVersion'].
   */
  private List<TCatalogObject> getDeletedObjects(long fromVersion, long toVersion) {
    versionLock_.readLock().lock();
    try {
      return deleteLog_.retrieveObjects(fromVersion, toVersion);
    } finally {
      versionLock_.readLock().unlock();
    }
  }

  /**
   * Get a snapshot view of all the databases in the catalog.
   */
  List<Db> getAllDbs() {
    versionLock_.readLock().lock();
    try {
      return ImmutableList.copyOf(dbCache_.get().values());
    } finally {
      versionLock_.readLock().unlock();
    }
  }

  /**
   * Get a snapshot view of all the data sources in the catalog.
   */
   private List<DataSource> getAllDataSources() {
    versionLock_.readLock().lock();
    try {
      return ImmutableList.copyOf(getDataSources());
    } finally {
      versionLock_.readLock().unlock();
    }
  }

  /**
   * Get a snapshot view of all the Hdfs cache pools in the catalog.
   */
  private List<HdfsCachePool> getAllHdfsCachePools() {
    versionLock_.readLock().lock();
    try {
      return ImmutableList.copyOf(hdfsCachePools_);
    } finally {
      versionLock_.readLock().unlock();
    }
  }

  /**
   * Get a snapshot view of all the roles in the catalog.
   */
  private List<Role> getAllRoles() {
    versionLock_.readLock().lock();
    try {
      return ImmutableList.copyOf(authPolicy_.getAllRoles());
    } finally {
      versionLock_.readLock().unlock();
    }
  }

  /**
   * Get a snapshot view of all the users in the catalog.
   */
  private List<User> getAllUsers() {
    versionLock_.readLock().lock();
    try {
      return ImmutableList.copyOf(authPolicy_.getAllUsers());
    } finally {
      versionLock_.readLock().unlock();
    }
  }

  /**
   * Get a snapshot view of all authz cache invalidation markers in the catalog.
   */
  private List<AuthzCacheInvalidation> getAllAuthzCacheInvalidation() {
    versionLock_.readLock().lock();
    try {
      return ImmutableList.copyOf(authzCacheInvalidation_);
    } finally {
      versionLock_.readLock().unlock();
    }
  }

  /**
   * Adds a database in the topic update if its version is in the range
   * ('ctx.fromVersion', 'ctx.toVersion']. It iterates through all the tables and
   * functions of this database to determine if they can be included in the topic update.
   */
  private void addDatabaseToCatalogDelta(Db db, GetCatalogDeltaContext ctx)
      throws TException {
    long dbVersion = db.getCatalogVersion();
    if (dbVersion > ctx.fromVersion && dbVersion <= ctx.toVersion) {
      TCatalogObject catalogDb =
          new TCatalogObject(TCatalogObjectType.DATABASE, dbVersion);
      catalogDb.setDb(db.toThrift());
      ctx.addCatalogObject(catalogDb, false);
    }
    for (Table tbl: getAllTables(db)) {
      addTableToCatalogDelta(tbl, ctx);
    }
    for (Function fn: getAllFunctions(db)) {
      addFunctionToCatalogDelta(fn, ctx);
    }
  }

  /**
   * Get a snapshot view of all the tables in a database.
   */
  List<Table> getAllTables(Db db) {
    Preconditions.checkNotNull(db);
    versionLock_.readLock().lock();
    try {
      return ImmutableList.copyOf(db.getTables());
    } finally {
      versionLock_.readLock().unlock();
    }
  }

  /**
   * Get a snapshot view of all the functions in a database.
   */
  private List<Function> getAllFunctions(Db db) {
    Preconditions.checkNotNull(db);
    versionLock_.readLock().lock();
    try {
      return ImmutableList.copyOf(db.getFunctions(null, new PatternMatcher()));
    } finally {
      versionLock_.readLock().unlock();
    }
  }

  /**
   * Given a database name and a property key returns the value of the key from the
   * parameters map of the HMS db object
   * @param dbName name of the database
   * @param propertyKey property key
   * @return value of key from the db parameter. returns null if Db is not found or key
   * does not exist in the parameters
   */
  public String getDbProperty(String dbName, String propertyKey) {
    Preconditions.checkNotNull(dbName);
    Preconditions.checkNotNull(propertyKey);
    versionLock_.readLock().lock();
    try {
      Db db = getDb(dbName);
      if (db == null) return null;
      if (!db.getMetaStoreDb().isSetParameters()) return null;
      return db.getMetaStoreDb().getParameters().get(propertyKey);
    } finally {
      versionLock_.readLock().unlock();
    }
  }

  /**
   * Given a dbname, table name and a key returns the value of the key from the cached
   * Table object's parameters
   * @return Value of the parameter which maps to property key, null if the table
   * doesn't exist, if it is a incomplete table or if the parameter is not found
   */
  public List<String> getTableProperties(
      String dbName, String tblName, List<String> propertyKeys) {
    Preconditions.checkNotNull(dbName);
    Preconditions.checkNotNull(tblName);
    Preconditions.checkNotNull(propertyKeys);
    versionLock_.readLock().lock();
    try {
      Db db = getDb(dbName);
      if (db == null) return null;
      Table tbl = db.getTable(tblName);
      if (tbl == null || tbl instanceof IncompleteTable) return null;
      if (!tbl.getMetaStoreTable().isSetParameters()) return null;
      List<String> propertyValues = new ArrayList<>(propertyKeys.size());
      for (String propertyKey : propertyKeys) {
        propertyValues.add(tbl.getMetaStoreTable().getParameters().get(propertyKey));
      }
      return propertyValues;
    } finally {
      versionLock_.readLock().unlock();
    }
  }

  /**
   * Updates the Db with the given metastore database object. Useful to doing in-place
   * updates to the HMS db like in case of changing owner, adding comment or setting
   * certain properties
   * @param msDb The HMS database object to be used to update
   * @return The updated Db object
   * @throws DatabaseNotFoundException if Db with the name provided by given Database
   * is not found in Catalog
   */
  public Db updateDb(Database msDb) throws DatabaseNotFoundException {
    Preconditions.checkNotNull(msDb);
    Preconditions.checkNotNull(msDb.getName());
    versionLock_.writeLock().lock();
    try {
      Db db = getDb(msDb.getName());
      if (db == null) {
        throw new DatabaseNotFoundException("Database " + msDb.getName() + " not found");
      }
      db.setMetastoreDb(msDb.getName(), msDb);
      db.setCatalogVersion(incrementAndGetCatalogVersion());
      return db;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Adds a table in the topic update if its version is in the range
   * ('ctx.fromVersion', 'ctx.toVersion']. If the table's version is larger than
   * 'ctx.toVersion' and the table has skipped a topic update
   * 'MAX_NUM_SKIPPED_TOPIC_UPDATES' times, it is included in the topic update. This
   * prevents tables that are updated frequently from skipping topic updates indefinitely,
   * which would also violate the semantics of SYNC_DDL.
   */
  private void addTableToCatalogDelta(Table tbl, GetCatalogDeltaContext ctx)
      throws TException  {
    if (tbl.getCatalogVersion() <= ctx.toVersion) {
      addTableToCatalogDeltaHelper(tbl, ctx);
    } else {
      TopicUpdateLog.Entry topicUpdateEntry =
          topicUpdateLog_.getOrCreateLogEntry(tbl.getUniqueName());
      Preconditions.checkNotNull(topicUpdateEntry);
      if (topicUpdateEntry.getNumSkippedTopicUpdates() == MAX_NUM_SKIPPED_TOPIC_UPDATES) {
        addTableToCatalogDeltaHelper(tbl, ctx);
      } else {
        LOG.info("Table {} (version={}) is skipping topic update ({}, {}]",
            tbl.getFullName(), tbl.getCatalogVersion(), ctx.fromVersion, ctx.toVersion);
        topicUpdateLog_.add(tbl.getUniqueName(),
            new TopicUpdateLog.Entry(
                topicUpdateEntry.getNumSkippedTopicUpdates() + 1,
                topicUpdateEntry.getLastSentVersion(),
                topicUpdateEntry.getLastSentCatalogUpdate()));
      }
    }
  }

  /**
   * Helper function that tries to add a table in a topic update. It acquires table's
   * lock and checks if its version is in the ('ctx.fromVersion', 'ctx.toVersion'] range
   * and how many consecutive times (if any) has the table skipped a topic update.
   */
  private void addTableToCatalogDeltaHelper(Table tbl, GetCatalogDeltaContext ctx)
      throws TException {
    TCatalogObject catalogTbl =
        new TCatalogObject(TCatalogObjectType.TABLE, Catalog.INITIAL_CATALOG_VERSION);
    tbl.getLock().lock();
    try {
      long tblVersion = tbl.getCatalogVersion();
      if (tblVersion <= ctx.fromVersion) return;
      String tableUniqueName = tbl.getUniqueName();
      TopicUpdateLog.Entry topicUpdateEntry =
          topicUpdateLog_.getOrCreateLogEntry(tableUniqueName);
      if (tblVersion > ctx.toVersion &&
          topicUpdateEntry.getNumSkippedTopicUpdates() < MAX_NUM_SKIPPED_TOPIC_UPDATES) {
        LOG.info("Table " + tbl.getFullName() + " is skipping topic update " +
            ctx.toVersion);
        topicUpdateLog_.add(tableUniqueName,
            new TopicUpdateLog.Entry(
                topicUpdateEntry.getNumSkippedTopicUpdates() + 1,
                topicUpdateEntry.getLastSentVersion(),
                topicUpdateEntry.getLastSentCatalogUpdate()));
        return;
      }
      try {
        catalogTbl.setTable(tbl.toThrift());
      } catch (Exception e) {
        LOG.error(String.format("Error calling toThrift() on table %s: %s",
            tbl.getFullName(), e.getMessage()), e);
        return;
      }
      catalogTbl.setCatalog_version(tbl.getCatalogVersion());
      ctx.addCatalogObject(catalogTbl, false);
    } finally {
      tbl.getLock().unlock();
    }
  }

  /**
   * Adds a function to the topic update if its version is in the range
   * ('ctx.fromVersion', 'ctx.toVersion'].
   */
  private void addFunctionToCatalogDelta(Function fn, GetCatalogDeltaContext ctx)
      throws TException {
    long fnVersion = fn.getCatalogVersion();
    if (ctx.versionNotInRange(fnVersion)) return;
    TCatalogObject function =
        new TCatalogObject(TCatalogObjectType.FUNCTION, fnVersion);
    function.setFn(fn.toThrift());
    ctx.addCatalogObject(function, false);
  }

  /**
   * Adds a data source to the topic update if its version is in the range
   * ('ctx.fromVersion', 'ctx.toVersion'].
   */
  private void addDataSourceToCatalogDelta(DataSource dataSource,
      GetCatalogDeltaContext ctx) throws TException  {
    long dsVersion = dataSource.getCatalogVersion();
    if (ctx.versionNotInRange(dsVersion)) return;
    TCatalogObject catalogObj =
        new TCatalogObject(TCatalogObjectType.DATA_SOURCE, dsVersion);
    catalogObj.setData_source(dataSource.toThrift());
    ctx.addCatalogObject(catalogObj, false);
  }

  /**
   * Adds a HDFS cache pool to the topic update if its version is in the range
   * ('ctx.fromVersion', 'ctx.toVersion'].
   */
  private void addHdfsCachePoolToCatalogDelta(HdfsCachePool cachePool,
      GetCatalogDeltaContext ctx) throws TException  {
    long cpVersion = cachePool.getCatalogVersion();
    if (ctx.versionNotInRange(cpVersion)) return;
    TCatalogObject pool =
        new TCatalogObject(TCatalogObjectType.HDFS_CACHE_POOL, cpVersion);
    pool.setCache_pool(cachePool.toThrift());
    ctx.addCatalogObject(pool, false);
  }


  /**
   * Adds a principal to the topic update if its version is in the range
   * ('ctx.fromVersion', 'ctx.toVersion']. It iterates through all the privileges of
   * this principal to determine if they can be inserted in the topic update.
   */
  private void addPrincipalToCatalogDelta(Principal principal, GetCatalogDeltaContext ctx)
      throws TException {
    long principalVersion = principal.getCatalogVersion();
    if (!ctx.versionNotInRange(principalVersion)) {
      TCatalogObject thriftPrincipal =
          new TCatalogObject(TCatalogObjectType.PRINCIPAL, principalVersion);
      thriftPrincipal.setPrincipal(principal.toThrift());
      ctx.addCatalogObject(thriftPrincipal, false);
    }
    for (PrincipalPrivilege p: getAllPrivileges(principal)) {
      addPrincipalPrivilegeToCatalogDelta(p, ctx);
    }
  }

  /**
   * Get a snapshot view of all the privileges in a principal.
   */
  private List<PrincipalPrivilege> getAllPrivileges(Principal principal) {
    Preconditions.checkNotNull(principal);
    versionLock_.readLock().lock();
    try {
      return ImmutableList.copyOf(principal.getPrivileges());
    } finally {
      versionLock_.readLock().unlock();
    }
  }

  /**
   * Adds a principal privilege to the topic update if its version is in the range
   * ('ctx.fromVersion', 'ctx.toVersion'].
   */
  private void addPrincipalPrivilegeToCatalogDelta(PrincipalPrivilege priv,
      GetCatalogDeltaContext ctx) throws TException  {
    long privVersion = priv.getCatalogVersion();
    if (ctx.versionNotInRange(privVersion)) return;
    TCatalogObject privilege =
        new TCatalogObject(TCatalogObjectType.PRIVILEGE, privVersion);
    privilege.setPrivilege(priv.toThrift());
    ctx.addCatalogObject(privilege, false);
  }

  /**
   * Adds an authz cache invalidation to the topic update if its version is in the range
   * ('ctx.fromVersion', 'ctx.toVersion'].
   */
  private void addAuthzCacheInvalidationToCatalogDelta(
      AuthzCacheInvalidation authzCacheInvalidation, GetCatalogDeltaContext ctx)
      throws TException  {
    long authzCacheInvalidationVersion = authzCacheInvalidation.getCatalogVersion();
    if (ctx.versionNotInRange(authzCacheInvalidationVersion)) return;
    TCatalogObject catalogObj = new TCatalogObject(
        TCatalogObjectType.AUTHZ_CACHE_INVALIDATION, authzCacheInvalidationVersion);
    catalogObj.setAuthz_cache_invalidation(authzCacheInvalidation.toThrift());
    ctx.addCatalogObject(catalogObj, false);
  }

  /**
   * Returns all user defined functions (aggregate and scalar) in the specified database.
   * Functions are not returned in a defined order.
   */
  public List<Function> getFunctions(String dbName) throws DatabaseNotFoundException {
    Db db = getDb(dbName);
    if (db == null) {
      throw new DatabaseNotFoundException("Database does not exist: " + dbName);
    }

    // Contains map of overloaded function names to all functions matching that name.
    Map<String, List<Function>> dbFns = db.getAllFunctions();
    List<Function> fns = new ArrayList<>(dbFns.size());
    for (List<Function> fnOverloads: dbFns.values()) {
      for (Function fn: fnOverloads) {
        fns.add(fn);
      }
    }
    return fns;
  }

  /**
   * Extracts Impala functions stored in metastore db parameters and adds them to
   * the catalog cache.
   */
  private void loadFunctionsFromDbParams(Db db,
      org.apache.hadoop.hive.metastore.api.Database msDb) {
    if (msDb == null || msDb.getParameters() == null) return;
    LOG.info("Loading native functions for database: " + db.getName());
    List<Function> funcs = FunctionUtils.deserializeNativeFunctionsFromDbParams(
        msDb.getParameters());
    for (Function f : funcs) {
      db.addFunction(f, false);
      f.setCatalogVersion(incrementAndGetCatalogVersion());
    }

    LOG.info("Loaded native functions for database: " + db.getName());
  }

  /**
   * Loads Java functions into the catalog. For each function in "functions",
   * we extract all Impala compatible evaluate() signatures and load them
   * as separate functions in the catalog.
   */
  private void loadJavaFunctions(Db db,
      List<org.apache.hadoop.hive.metastore.api.Function> functions) {
    Preconditions.checkNotNull(functions);
    if (BackendConfig.INSTANCE.disableCatalogDataOpsDebugOnly()) {
      LOG.info("Skip loading Java functions: catalog data ops disabled.");
      return;
    }
    LOG.info("Loading Java functions for database: " + db.getName());
    for (org.apache.hadoop.hive.metastore.api.Function function: functions) {
      try {
        List<Function> fns = FunctionUtils.extractFunctions(db.getName(), function,
            localLibraryPath_);
        for (Function fn: fns) {
          db.addFunction(fn);
          fn.setCatalogVersion(incrementAndGetCatalogVersion());
        }
      } catch (Exception e) {
        LOG.error("Skipping function load: " + function.getFunctionName(), e);
      }
    }
    LOG.info("Loaded Java functions for database: " + db.getName());
  }

  /**
   * Reloads function metadata for 'dbName' database. Populates the 'addedFuncs' list
   * with functions that were added as a result of this operation. Populates the
   * 'removedFuncs' list with functions that were removed.
   */
  public void refreshFunctions(MetaStoreClient msClient, String dbName,
      List<TCatalogObject> addedFuncs, List<TCatalogObject> removedFuncs)
      throws CatalogException {
    // Create a temporary database that will contain all the functions from the HMS.
    Db tmpDb;
    try {
      List<org.apache.hadoop.hive.metastore.api.Function> javaFns =
          new ArrayList<>();
      for (String javaFn : msClient.getHiveClient().getFunctions(dbName, "*")) {
        javaFns.add(msClient.getHiveClient().getFunction(dbName, javaFn));
      }
      // Contains native functions in it's params map.
      org.apache.hadoop.hive.metastore.api.Database msDb =
          msClient.getHiveClient().getDatabase(dbName);
      tmpDb = new Db(dbName, msDb);
      // Load native UDFs into the temporary db.
      loadFunctionsFromDbParams(tmpDb, msDb);
      // Load Java UDFs from HMS into the temporary db.
      loadJavaFunctions(tmpDb, javaFns);

      Db db = getDb(dbName);
      if (db == null) {
        throw new DatabaseNotFoundException("Database does not exist: " + dbName);
      }
      // Load transient functions into the temporary db.
      for (Function fn: db.getTransientFunctions()) tmpDb.addFunction(fn);

      // Compute the removed functions and remove them from the db.
      for (Map.Entry<String, List<Function>> e: db.getAllFunctions().entrySet()) {
        for (Function fn: e.getValue()) {
          if (tmpDb.getFunction(
              fn, Function.CompareMode.IS_INDISTINGUISHABLE) == null) {
            fn.setCatalogVersion(incrementAndGetCatalogVersion());
            removedFuncs.add(fn.toTCatalogObject());
          }
        }
      }

      // We will re-add all the functions to the db because it's possible that a
      // function was dropped and a different function (for example, the binary is
      // different) with the same name and signature was re-added in Hive.
      db.removeAllFunctions();
      for (Map.Entry<String, List<Function>> e: tmpDb.getAllFunctions().entrySet()) {
        for (Function fn: e.getValue()) {
          // We do not need to increment and acquire a new catalog version for this
          // function here because this already happens when the functions are loaded
          // into tmpDb.
          db.addFunction(fn);
          addedFuncs.add(fn.toTCatalogObject());
        }
      }

    } catch (Exception e) {
      throw new CatalogException("Error refreshing functions in " + dbName + ": ", e);
    }
  }

  /**
   * Invalidates the database 'db'. This method can have potential race
   * conditions with external changes to the Hive metastore and hence any
   * conflicting changes to the objects can manifest in the form of exceptions
   * from the HMS calls which are appropriately handled. Returns the invalidated
   * 'Db' object along with list of tables to be loaded by the TableLoadingMgr.
   * Returns null if the method encounters an exception during invalidation.
   */
  private Pair<Db, List<TTableName>> invalidateDb(
      MetaStoreClient msClient, String dbName, Db existingDb) {
    try {
      List<org.apache.hadoop.hive.metastore.api.Function> javaFns =
          new ArrayList<>();
      for (String javaFn: msClient.getHiveClient().getFunctions(dbName, "*")) {
        javaFns.add(msClient.getHiveClient().getFunction(dbName, javaFn));
      }
      org.apache.hadoop.hive.metastore.api.Database msDb =
          msClient.getHiveClient().getDatabase(dbName);
      Db newDb = new Db(dbName, msDb);
      // existingDb is usually null when the Catalog loads for the first time.
      // In that case we needn't restore any transient functions.
      if (existingDb != null) {
        // Restore UDFs that aren't persisted. They are only cleaned up on
        // Catalog restart.
        for (Function fn: existingDb.getTransientFunctions()) {
          newDb.addFunction(fn);
          fn.setCatalogVersion(incrementAndGetCatalogVersion());
        }
      }
      // Reload native UDFs.
      loadFunctionsFromDbParams(newDb, msDb);
      // Reload Java UDFs from HMS.
      loadJavaFunctions(newDb, javaFns);
      newDb.setCatalogVersion(incrementAndGetCatalogVersion());

      List<TTableName> tblsToBackgroundLoad = new ArrayList<>();
      for (String tableName: msClient.getHiveClient().getAllTables(dbName)) {
        if (isBlacklistedTable(dbName, tableName.toLowerCase())) {
          LOG.info("skip blacklisted table: " + dbName + "." + tableName);
          continue;
        }
        Table incompleteTbl = IncompleteTable.createUninitializedTable(newDb, tableName);
        incompleteTbl.setCatalogVersion(incrementAndGetCatalogVersion());
        newDb.addTable(incompleteTbl);
        if (loadInBackground_) {
          tblsToBackgroundLoad.add(new TTableName(dbName, tableName.toLowerCase()));
        }
      }

      if (existingDb != null) {
        // Identify any removed functions and add them to the delta log.
        for (Map.Entry<String, List<Function>> e:
             existingDb.getAllFunctions().entrySet()) {
          for (Function fn: e.getValue()) {
            if (newDb.getFunction(fn,
                Function.CompareMode.IS_INDISTINGUISHABLE) == null) {
              fn.setCatalogVersion(incrementAndGetCatalogVersion());
              deleteLog_.addRemovedObject(fn.toTCatalogObject());
            }
          }
        }

        // Identify any deleted tables and add them to the delta log
        Set<String> oldTableNames = Sets.newHashSet(existingDb.getAllTableNames());
        Set<String> newTableNames = Sets.newHashSet(newDb.getAllTableNames());
        oldTableNames.removeAll(newTableNames);
        for (String removedTableName: oldTableNames) {
          Table removedTable = IncompleteTable.createUninitializedTable(existingDb,
              removedTableName);
          removedTable.setCatalogVersion(incrementAndGetCatalogVersion());
          deleteLog_.addRemovedObject(removedTable.toTCatalogObject());
        }
      }
      return Pair.create(newDb, tblsToBackgroundLoad);
    } catch (Exception e) {
      LOG.warn("Encountered an exception while invalidating database: " + dbName +
          ". Ignoring further load of this db.", e);
    }
    return null;
  }

  /**
   * Refreshes authorization metadata. When authorization is not enabled, this
   * method is a no-op.
   */
  public AuthorizationDelta refreshAuthorization(boolean resetVersions)
      throws CatalogException {
    Preconditions.checkState(authzManager_ != null);
    try {
      return authzManager_.refreshAuthorization(resetVersions);
    } catch (Exception e) {
      throw new CatalogException("Error refreshing authorization policy: ", e);
    }
  }

  /**
   * Resets this catalog instance by clearing all cached table and database metadata.
   * Returns the current catalog version before reset has taken any effect. The
   * requesting impalad will use that version to determine when the
   * effects of reset have been applied to its local catalog cache.
   */
  public long reset() throws CatalogException {
    long startVersion = getCatalogVersion();
    LOG.info("Invalidating all metadata. Version: " + startVersion);
    // First update the policy metadata.
    refreshAuthorization(true);

    // Even though we get the current notification event id before stopping the event
    // processing here there is a small window of time where we could re-process some of
    // the event ids, if there is external DDL activity on metastore during reset.
    // Unfortunately, there is no good way to avoid this since HMS does not provide
    // APIs which can fetch all the tables/databases at a given id. It is OKAY to
    // re-process some of these events since event processor relies on creationTime of
    // the objects to uniquely identify tables from create and drop events. In case of
    // alter events, however it is likely that some tables would be unnecessarily
    // invalidated. That would happen when during reset, there were external alter events
    // and by the time we processed them, Catalog had already loaded them.
    long currentEventId = metastoreEventProcessor_.getCurrentEventId();
    // pause the event processing since the cache is anyways being cleared
    metastoreEventProcessor_.pause();
    // Update the HDFS cache pools
    CachePoolReader reader = new CachePoolReader(true);
    reader.run();
    versionLock_.writeLock().lock();
    // In case of an empty new catalog, the version should still change to reflect the
    // reset operation itself and to unblock impalads by making the catalog version >
    // INITIAL_CATALOG_VERSION. See Frontend.waitForCatalog()
    ++catalogVersion_;
    // Assign new versions to all the loaded data sources.
    for (DataSource dataSource: getDataSources()) {
      dataSource.setCatalogVersion(incrementAndGetCatalogVersion());
    }

    // Update db and table metadata
    try {
      // Not all Java UDFs are persisted to the metastore. The ones which aren't
      // should be restored once the catalog has been invalidated.
      Map<String, Db> oldDbCache = dbCache_.get();

      // Build a new DB cache, populate it, and replace the existing cache in one
      // step.
      Map<String, Db> newDbCache = new ConcurrentHashMap<String, Db>();
      List<TTableName> tblsToBackgroundLoad = new ArrayList<>();
      try (MetaStoreClient msClient = getMetaStoreClient()) {
        List<String> allDbs = msClient.getHiveClient().getAllDatabases();
        int numComplete = 0;
        for (String dbName: allDbs) {
          if (isBlacklistedDb(dbName)) {
            LOG.info("skip blacklisted db: " + dbName);
            continue;
          }
          String annotation = String.format("invalidating metadata - %s/%s dbs complete",
              numComplete++, allDbs.size());
          try (ThreadNameAnnotator tna = new ThreadNameAnnotator(annotation)) {
            dbName = dbName.toLowerCase();
            Db oldDb = oldDbCache.get(dbName);
            // invalidateDb() will return empty table list
            // if loadInBackground_ is set to false
            Pair<Db, List<TTableName>> invalidatedDb = invalidateDb(msClient,
                dbName, oldDb);
            if (invalidatedDb == null) continue;
            newDbCache.put(dbName, invalidatedDb.first);
            tblsToBackgroundLoad.addAll(invalidatedDb.second);
          }
        }
      }
      dbCache_.set(newDbCache);

      // Identify any deleted databases and add them to the delta log.
      Set<String> oldDbNames = oldDbCache.keySet();
      Set<String> newDbNames = newDbCache.keySet();
      oldDbNames.removeAll(newDbNames);
      for (String dbName: oldDbNames) {
        Db removedDb = oldDbCache.get(dbName);
        updateDeleteLog(removedDb);
      }

      // Submit tables for background loading.
      for (TTableName tblName: tblsToBackgroundLoad) {
        tableLoadingMgr_.backgroundLoad(tblName);
      }
    } catch (Exception e) {
      LOG.error("Error initializing Catalog", e);
      throw new CatalogException("Error initializing Catalog. Catalog may be empty.", e);
    } finally {
      // It's possible that concurrent reset() gets a startVersion later than us but
      // acquires the version lock before us so the lastResetStartVersion_ is already
      // bumped. Don't need to update it in this case.
      if (lastResetStartVersion_ < startVersion) lastResetStartVersion_ = startVersion;
      versionLock_.writeLock().unlock();
      // restart the event processing for id just before the reset
      metastoreEventProcessor_.start(currentEventId);
    }
    LOG.info("Invalidated all metadata.");
    return startVersion;
  }

  /**
   * Adds a database name to the metadata cache and returns the database's
   * new Db object. Used by CREATE DATABASE statements.
   */
  public Db addDb(String dbName, org.apache.hadoop.hive.metastore.api.Database msDb) {
    Db newDb = new Db(dbName, msDb);
    versionLock_.writeLock().lock();
    try {
      newDb.setCatalogVersion(incrementAndGetCatalogVersion());
      addDb(newDb);
      return newDb;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Adds a database name to the metadata cache if not exists and returns the
   * true is a new Db Object was added. Used by MetastoreEventProcessor to handle
   * CREATE_DATABASE events
   */
  public boolean addDbIfNotExists(
      String dbName, org.apache.hadoop.hive.metastore.api.Database msDb) {
    versionLock_.writeLock().lock();
    try {
      Db db = getDb(dbName);
      if (db == null) {
        return addDb(dbName, msDb) != null;
      }
      return false;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Removes a database from the metadata cache and returns the removed database,
   * or null if the database did not exist in the cache.
   * Used by DROP DATABASE statements.
   */
  @Override
  public Db removeDb(String dbName) {
    versionLock_.writeLock().lock();
    try {
      Db removedDb = super.removeDb(dbName);
      if (removedDb != null) updateDeleteLog(removedDb);
      return removedDb;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * @param msDb Metastore Database used to remove Db from Catalog
   * @param dbFound Set to true if Database is found in Catalog
   * @param dbMatched Set to true if Database is found in Catalog and it's CREATION_TIME
   * is equal to the metastore DB
   * @return the DB object removed. Return null if DB does not exist or was not removed
   * because CREATION_TIME does not match.
   */
  public Db removeDbIfExists(org.apache.hadoop.hive.metastore.api.Database msDb,
      Reference<Boolean> dbFound, Reference<Boolean> dbMatched) {
    dbFound.setRef(false);
    dbMatched.setRef(false);
    versionLock_.writeLock().lock();
    try {
      String dbName = msDb.getName();
      Db catalogDb = getDb(dbName);
      if (catalogDb == null) return null;

      dbFound.setRef(true);
      // Remove the DB only if the CREATION_TIME matches with the metastore DB from event.
      if (msDb.getCreateTime() == catalogDb.getMetaStoreDb().getCreateTime()) {
        Db removedDb = removeDb(dbName);
        if (removedDb != null) {
          dbMatched.setRef(true);
          return removedDb;
        }
      }
      return null;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Helper function to clean up the state associated with a removed database. It creates
   * the entries in the delete log for 'db' as well as for its tables and functions
   * (if any).
   */
  private void updateDeleteLog(Db db) {
    Preconditions.checkNotNull(db);
    Preconditions.checkState(versionLock_.isWriteLockedByCurrentThread());
    if (!db.isSystemDb()) {
      for (Table tbl: db.getTables()) {
        tbl.setCatalogVersion(incrementAndGetCatalogVersion());
        deleteLog_.addRemovedObject(tbl.toMinimalTCatalogObject());
      }
      for (Function fn: db.getFunctions(null, new PatternMatcher())) {
        fn.setCatalogVersion(incrementAndGetCatalogVersion());
        deleteLog_.addRemovedObject(fn.toTCatalogObject());
      }
    }
    db.setCatalogVersion(incrementAndGetCatalogVersion());
    deleteLog_.addRemovedObject(db.toTCatalogObject());
  }

  /**
   * Adds table with the given db and table name to the catalog if it does not exists.
   * @return true if the table was successfully added and false if the table already
   * exists
   * @throws CatalogException if the db is not found
   */
  public boolean addTableIfNotExists(String dbName, String tblName)
      throws CatalogException {
    versionLock_.writeLock().lock();
    try {
      Db db = getDb(dbName);
      if (db == null) {
        throw new CatalogException(String.format("Db %s does not exist", dbName));
      }
      Table existingTable = db.getTable(tblName);
      if (existingTable != null) return false;
      Table incompleteTable = IncompleteTable.createUninitializedTable(db, tblName);
      incompleteTable.setCatalogVersion(incrementAndGetCatalogVersion());
      db.addTable(incompleteTable);
      return true;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Adds a table with the given name to the catalog and returns the new table.
   */
  public Table addIncompleteTable(String dbName, String tblName) {
    versionLock_.writeLock().lock();
    try {
      // IMPALA-9211: get db object after holding the writeLock in case of getting stale
      // db object due to concurrent INVALIDATE METADATA
      Db db = getDb(dbName);
      if (db == null) return null;
      Table incompleteTable = IncompleteTable.createUninitializedTable(db, tblName);
      incompleteTable.setCatalogVersion(incrementAndGetCatalogVersion());
      db.addTable(incompleteTable);
      return db.getTable(tblName);
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Adds a table 'table' to the database 'db' and returns the table that was added.
   */
  public Table addTable(Db db, Table table) {
    versionLock_.writeLock().lock();
    try {
      Preconditions.checkNotNull(db).addTable(Preconditions.checkNotNull(table));
    } finally {
      versionLock_.writeLock().unlock();
    }
    return table;
  }

  /**
   * Gets the table with the given name, loading it if needed (if the existing catalog
   * object is not yet loaded). Returns the matching Table or null if no table with this
   * name exists in the catalog.
   * If the existing table is dropped or modified (indicated by the catalog version
   * changing) while the load is in progress, the loaded value will be discarded
   * and the current cached value will be returned. This may mean that a missing table
   * (not yet loaded table) will be returned.
   */
  public Table getOrLoadTable(String dbName, String tblName, String reason)
      throws CatalogException {
    TTableName tableName = new TTableName(dbName.toLowerCase(), tblName.toLowerCase());
    TableLoadingMgr.LoadRequest loadReq;

    long previousCatalogVersion;
    // Return the table if it is already loaded or submit a new load request.
    versionLock_.readLock().lock();
    try {
      Table tbl = getTable(dbName, tblName);
      if (tbl == null || tbl.isLoaded()) return tbl;
      previousCatalogVersion = tbl.getCatalogVersion();
      loadReq = tableLoadingMgr_.loadAsync(tableName, reason);
    } finally {
      versionLock_.readLock().unlock();
    }
    Preconditions.checkNotNull(loadReq);
    try {
      // The table may have been dropped/modified while the load was in progress, so only
      // apply the update if the existing table hasn't changed.
      return replaceTableIfUnchanged(loadReq.get(), previousCatalogVersion);
    } finally {
      loadReq.close();
    }
  }

  /**
   * Replaces an existing Table with a new value if it exists and has not changed
   * (has the same catalog version as 'expectedCatalogVersion').
   */
  private Table replaceTableIfUnchanged(Table updatedTbl, long expectedCatalogVersion)
      throws DatabaseNotFoundException {
    versionLock_.writeLock().lock();
    try {
      Db db = getDb(updatedTbl.getDb().getName());
      if (db == null) {
        throw new DatabaseNotFoundException(
            "Database does not exist: " + updatedTbl.getDb().getName());
      }

      Table existingTbl = db.getTable(updatedTbl.getName());
      // The existing table does not exist or has been modified. Instead of
      // adding the loaded value, return the existing table.
      if (existingTbl == null ||
          existingTbl.getCatalogVersion() != expectedCatalogVersion) return existingTbl;

      updatedTbl.setCatalogVersion(incrementAndGetCatalogVersion());
      db.addTable(updatedTbl);
      return updatedTbl;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Remove a catalog table based on the given metastore table if it exists and its
   * createTime matches with the metastore table
   *
   * @param msTable Metastore table to be used to remove Table
   * @param tblWasfound is set to true if the table was found in the catalog
   * @param tblMatched is set to true if the table is found and it matched with the
   * createTime of the cached metastore table in catalog or if the existing table is a
   * incomplete table
   * @return Removed table object. Return null if the table was not removed
   */
  public Table removeTableIfExists(org.apache.hadoop.hive.metastore.api.Table msTable,
      Reference<Boolean> tblWasfound, Reference<Boolean> tblMatched) {
    tblWasfound.setRef(false);
    tblMatched.setRef(false);
    // make sure that the createTime of the input table is valid
    Preconditions.checkState(msTable.getCreateTime() > 0);
    versionLock_.writeLock().lock();
    try {
      Db db = getDb(msTable.getDbName());
      if (db == null) return null;

      Table tblToBeRemoved = db.getTable(msTable.getTableName());
      if (tblToBeRemoved == null) return null;

      tblWasfound.setRef(true);
      // make sure that you are removing the same instance of the table object which
      // is given by comparing the metastore createTime. In case the found table is a
      // Incomplete table remove it
      if (tblToBeRemoved instanceof IncompleteTable
          || (msTable.getCreateTime()
                 == tblToBeRemoved.getMetaStoreTable().getCreateTime())) {
        tblMatched.setRef(true);
        Table removedTbl = db.removeTable(tblToBeRemoved.getName());
        removedTbl.setCatalogVersion(incrementAndGetCatalogVersion());
        deleteLog_.addRemovedObject(removedTbl.toMinimalTCatalogObject());
        return removedTbl;
      }
      return null;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Removes a table from the catalog and increments the catalog version.
   * Returns the removed Table, or null if the table or db does not exist.
   */
  public Table removeTable(String dbName, String tblName) {
    Db parentDb = getDb(dbName);
    if (parentDb == null) return null;
    versionLock_.writeLock().lock();
    try {
      Table removedTable = parentDb.removeTable(tblName);
      if (removedTable != null) {
        removedTable.setCatalogVersion(incrementAndGetCatalogVersion());
        deleteLog_.addRemovedObject(removedTable.toMinimalTCatalogObject());
      }
      return removedTable;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Removes a function from the catalog. Increments the catalog version and returns
   * the Function object that was removed. If the function did not exist, null will
   * be returned.
   */
  @Override
  public Function removeFunction(Function desc) {
    versionLock_.writeLock().lock();
    try {
      Function removedFn = super.removeFunction(desc);
      if (removedFn != null) {
        removedFn.setCatalogVersion(incrementAndGetCatalogVersion());
        deleteLog_.addRemovedObject(removedFn.toTCatalogObject());
      }
      return removedFn;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Adds a function from the catalog, incrementing the catalog version. Returns true if
   * the add was successful, false otherwise.
   */
  @Override
  public boolean addFunction(Function fn) {
    Db db = getDb(fn.getFunctionName().getDb());
    if (db == null) return false;
    versionLock_.writeLock().lock();
    try {
      if (db.addFunction(fn)) {
        fn.setCatalogVersion(incrementAndGetCatalogVersion());
        return true;
      }
    } finally {
      versionLock_.writeLock().unlock();
    }
    return false;
  }

  /**
   * Adds a data source to the catalog, incrementing the catalog version. Returns true
   * if the add was successful, false otherwise.
   */
  @Override
  public boolean addDataSource(DataSource dataSource) {
    versionLock_.writeLock().lock();
    try {
      if (dataSources_.add(dataSource)) {
        dataSource.setCatalogVersion(incrementAndGetCatalogVersion());
        return true;
      }
    } finally {
      versionLock_.writeLock().unlock();
    }
    return false;
  }

  @Override
  public DataSource removeDataSource(String dataSourceName) {
    versionLock_.writeLock().lock();
    try {
      DataSource dataSource = dataSources_.remove(dataSourceName);
      if (dataSource != null) {
        dataSource.setCatalogVersion(incrementAndGetCatalogVersion());
        deleteLog_.addRemovedObject(dataSource.toTCatalogObject());
      }
      return dataSource;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Renames a table. Equivalent to an atomic drop + add of the table. Returns
   * a pair of tables containing the removed table (or null if the table drop was not
   * successful) and the new table (or null if either the drop of the old one or the
   * add of the new table was not successful). Depending on the return value, the catalog
   * cache is in one of the following states:
   * 1. null, null: Old table was not removed and new table was not added.
   * 2. null, T_new: Invalid configuration
   * 3. T_old, null: Old table was removed but new table was not added.
   * 4. T_old, T_new: Old table was removed and new table was added.
   */
  public Pair<Table, Table> renameTable(
      TTableName oldTableName, TTableName newTableName) {
    // Remove the old table name from the cache and add the new table.
    Db db = getDb(oldTableName.getDb_name());
    if (db == null) return null;
    versionLock_.writeLock().lock();
    try {
      Table oldTable =
          removeTable(oldTableName.getDb_name(), oldTableName.getTable_name());
      if (oldTable == null) return Pair.create(null, null);
      return Pair.create(oldTable,
          addIncompleteTable(newTableName.getDb_name(), newTableName.getTable_name()));
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Renames the table by atomically removing oldTable and adding the newTable.
   * @return true if oldTable was removed and newTable was added, false if oldTable or
   * either of oldDb or newDb is not in catalog.
   */
  public boolean renameTableIfExists(TTableName oldTableName,
      TTableName newTableName) {
    boolean tableRenamed = false;
    versionLock_.writeLock().lock();
    try {
      Db oldDb = getDb(oldTableName.db_name);
      Db newDb = getDb(newTableName.db_name);
      if (oldDb != null && newDb != null) {
        Table existingTable = removeTable(oldTableName.db_name, oldTableName.table_name);
        // Add the newTable only if oldTable existed.
        if (existingTable != null) {
          Table incompleteTable = IncompleteTable.createUninitializedTable(newDb,
              newTableName.getTable_name());
          incompleteTable.setCatalogVersion(incrementAndGetCatalogVersion());
          newDb.addTable(incompleteTable);
          tableRenamed = true;
        }
      }
      return tableRenamed;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Reloads metadata for table 'tbl' which must not be an IncompleteTable. Updates the
   * table metadata in-place by calling load() on the given table. Returns the
   * TCatalogObject representing 'tbl'. Applies proper synchronization to protect the
   * metadata load from concurrent table modifications and assigns a new catalog version.
   * Throws a CatalogException if there is an error loading table metadata.
   */
  public TCatalogObject reloadTable(Table tbl, String reason) throws CatalogException {
    LOG.info(String.format("Refreshing table metadata: %s", tbl.getFullName()));
    Preconditions.checkState(!(tbl instanceof IncompleteTable));
    String dbName = tbl.getDb().getName();
    String tblName = tbl.getName();
    if (!tryLockTable(tbl)) {
      throw new CatalogException(String.format("Error refreshing metadata for table " +
          "%s due to lock contention", tbl.getFullName()));
    }
    final Timer.Context context =
        tbl.getMetrics().getTimer(Table.REFRESH_DURATION_METRIC).time();
    try {
      long newCatalogVersion = incrementAndGetCatalogVersion();
      versionLock_.writeLock().unlock();
      try (MetaStoreClient msClient = getMetaStoreClient()) {
        org.apache.hadoop.hive.metastore.api.Table msTbl = null;
        Stopwatch hmsLoadSW = new Stopwatch().start();
        long hmsLoadTime;
        try {
          msTbl = msClient.getHiveClient().getTable(dbName, tblName);
        } catch (Exception e) {
          throw new TableLoadingException("Error loading metadata for table: " +
              dbName + "." + tblName, e);
        } finally {
          hmsLoadTime = hmsLoadSW.elapsed(TimeUnit.NANOSECONDS);
        }
        tbl.updateHMSLoadTableSchemaTime(hmsLoadTime);
        tbl.load(true, msClient.getHiveClient(), msTbl, reason);
      }
      tbl.setCatalogVersion(newCatalogVersion);
      LOG.info(String.format("Refreshed table metadata: %s", tbl.getFullName()));
      return tbl.toTCatalogObject();
    } finally {
      context.stop();
      Preconditions.checkState(!versionLock_.isWriteLockedByCurrentThread());
      tbl.getLock().unlock();
    }
  }

  /**
   * Drops the partitions specified in 'partitionSet' from 'tbl'. Throws a
   * CatalogException if 'tbl' is not an HdfsTable. Returns the target table.
   */
  public Table dropPartitions(Table tbl, List<List<TPartitionKeyValue>> partitionSet)
      throws CatalogException {
    Preconditions.checkNotNull(tbl);
    Preconditions.checkNotNull(partitionSet);
    Preconditions.checkArgument(tbl.getLock().isHeldByCurrentThread());
    if (!(tbl instanceof HdfsTable)) {
      throw new CatalogException("Table " + tbl.getFullName() + " is not an Hdfs table");
    }
    HdfsTable hdfsTable = (HdfsTable) tbl;
    List<HdfsPartition> partitions =
        hdfsTable.getPartitionsFromPartitionSet(partitionSet);
    hdfsTable.dropPartitions(partitions);
    return hdfsTable;
  }

  /**
   * Adds a partition to its HdfsTable and returns the modified table.
   */
  public Table addPartition(HdfsPartition partition) throws CatalogException {
    Preconditions.checkNotNull(partition);
    HdfsTable hdfsTable = partition.getTable();
    hdfsTable.addPartition(partition);
    return hdfsTable;
  }

  /**
   * Invalidates the table in the catalog cache, potentially adding/removing the table
   * from the cache based on whether it exists in the Hive Metastore.
   * The invalidation logic is:
   * - If the table exists in the Metastore, add it to the catalog as an uninitialized
   *   IncompleteTable (replacing any existing entry). The table metadata will be
   *   loaded lazily, on the next access. If the parent database for this table does not
   *   yet exist in Impala's cache it will also be added.
   * - If the table does not exist in the Metastore, remove it from the catalog cache.
   * - If we are unable to determine whether the table exists in the Metastore (there was
   *   an exception thrown making the RPC), invalidate any existing Table by replacing
   *   it with an uninitialized IncompleteTable.
   * Returns the thrift representation of the added/updated/removed table, or null if
   * the table was not present in the catalog cache or the Metastore.
   * Sets tblWasRemoved to true if the table was absent from the Metastore and it was
   * removed from the catalog cache.
   * Sets dbWasAdded to true if both a new database and table were added to the catalog
   * cache.
   */
  public TCatalogObject invalidateTable(TTableName tableName,
      Reference<Boolean> tblWasRemoved, Reference<Boolean> dbWasAdded) {
    tblWasRemoved.setRef(false);
    dbWasAdded.setRef(false);
    String dbName = tableName.getDb_name();
    String tblName = tableName.getTable_name();
    if (isBlacklistedTable(dbName, tblName)) {
      LOG.info("Skip invalidating blacklisted table: " + tableName);
      return null;
    }
    LOG.info(String.format("Invalidating table metadata: %s.%s", dbName, tblName));

    // Stores whether the table exists in the metastore. Can have three states:
    // 1) true - Table exists in metastore.
    // 2) false - Table does not exist in metastore.
    // 3) unknown (null) - There was exception thrown by the metastore client.
    Boolean tableExistsInMetaStore;
    Db db = null;
    try (MetaStoreClient msClient = getMetaStoreClient()) {
      org.apache.hadoop.hive.metastore.api.Database msDb = null;
      try {
        tableExistsInMetaStore = msClient.getHiveClient().tableExists(dbName, tblName);
      } catch (UnknownDBException e) {
        // The parent database does not exist in the metastore. Treat this the same
        // as if the table does not exist.
        tableExistsInMetaStore = false;
      } catch (TException e) {
        LOG.error("Error executing tableExists() metastore call: " + tblName, e);
        tableExistsInMetaStore = null;
      }

      if (tableExistsInMetaStore != null && !tableExistsInMetaStore) {
        Table result = removeTable(dbName, tblName);
        if (result == null) return null;
        tblWasRemoved.setRef(true);
        result.getLock().lock();
        try {
          return result.toTCatalogObject();
        } finally {
          result.getLock().unlock();
        }
      }

      db = getDb(dbName);
      if ((db == null || !db.containsTable(tblName)) && tableExistsInMetaStore == null) {
        // The table does not exist in our cache AND it is unknown whether the
        // table exists in the Metastore. Do nothing.
        return null;
      } else if (db == null && tableExistsInMetaStore) {
        // The table exists in the Metastore, but our cache does not contain the parent
        // database. A new db will be added to the cache along with the new table. msDb
        // must be valid since tableExistsInMetaStore is true.
        try {
          msDb = msClient.getHiveClient().getDatabase(dbName);
          Preconditions.checkNotNull(msDb);
          addDb(dbName, msDb);
          dbWasAdded.setRef(true);
        } catch (TException e) {
          // The Metastore database cannot be get. Log the error and return.
          LOG.error("Error executing getDatabase() metastore call: " + dbName, e);
          return null;
        }
      }
    }

    // Add a new uninitialized table to the table cache, effectively invalidating
    // any existing entry. The metadata for the table will be loaded lazily, on the
    // on the next access to the table.
    Table newTable = addIncompleteTable(dbName, tblName);
    Preconditions.checkNotNull(newTable);
    if (loadInBackground_) {
      tableLoadingMgr_.backgroundLoad(new TTableName(dbName.toLowerCase(),
          tblName.toLowerCase()));
    }
    if (dbWasAdded.getRef()) {
      // The database should always have a lower catalog version than the table because
      // it needs to be created before the table can be added.
      Db addedDb = newTable.getDb();
      Preconditions.checkNotNull(addedDb);
      Preconditions.checkState(
          addedDb.getCatalogVersion() < newTable.getCatalogVersion());
    }
    return newTable.toTCatalogObject();
  }

  /**
   * Invalidate the table if it exists by overwriting existing entry by a Incomplete
   * Table.
   * @return null if the table does not exist else return the invalidated table
   */
  public Table invalidateTableIfExists(String dbName, String tblName) {
    Table incompleteTable;
    versionLock_.writeLock().lock();
    try {
      Db db = getDb(dbName);
      if (db == null) return null;
      if (!db.containsTable(tblName)) return null;
      incompleteTable = IncompleteTable.createUninitializedTable(db, tblName);
      incompleteTable.setCatalogVersion(incrementAndGetCatalogVersion());
      db.addTable(incompleteTable);
    } finally {
      versionLock_.writeLock().unlock();
    }
    if (loadInBackground_) {
      tableLoadingMgr_.backgroundLoad(
          new TTableName(dbName.toLowerCase(), tblName.toLowerCase()));
    }
    return incompleteTable;
  }

  /**
   * Refresh partition if it exists.
   *
   * @return true if partition was reloaded, else false.
   * @throws CatalogException if partition reload threw an error.
   * @throws DatabaseNotFoundException if Db doesn't exist.
   * @throws TableNotFoundException if table doesn't exist.
   * @throws TableNotLoadedException if table is not loaded in Catalog.
   */
  public boolean reloadPartitionIfExists(String dbName, String tblName,
      List<TPartitionKeyValue> tPartSpec, String reason) throws CatalogException {
    Table table = getTable(dbName, tblName);
    if (table == null) {
      throw new TableNotFoundException(dbName + "." + tblName + " not found");
    }
    if (table instanceof IncompleteTable) {
      throw new TableNotLoadedException(dbName + "." + tblName + " is not loaded");
    }
    Reference<Boolean> wasPartitionRefreshed = new Reference<>(false);
    reloadPartition(table, tPartSpec, wasPartitionRefreshed, reason);
    return wasPartitionRefreshed.getRef();
  }

  /**
   * Refresh table if exists. Returns true if reloadTable() succeeds, false
   * otherwise. Throws CatalogException if reloadTable() is unsuccessful. Throws
   * DatabaseNotFoundException if Db doesn't exist.
   */
  public boolean reloadTableIfExists(String dbName, String tblName, String reason)
      throws CatalogException {
    Table table = getTable(dbName, tblName);
    if (table == null || table instanceof IncompleteTable) return false;
    reloadTable(table, reason);
    return true;
  }

  /**
   * Update DB if it exists in catalog. Returns true if updateDb() succeeds, false
   * otherwise.
   */
  public boolean updateDbIfExists(Database msdb) {
    try {
      updateDb(msdb);
    } catch (DatabaseNotFoundException e) {
      return false;
    }
    return true;
  }

  /**
   * Adds a new role with the given name and grant groups to the AuthorizationPolicy.
   * If a role with the same name already exists it will be overwritten.
   */
  public Role addRole(String roleName, Set<String> grantGroups) {
    Principal role = addPrincipal(roleName, grantGroups, TPrincipalType.ROLE);
    Preconditions.checkState(role instanceof Role);
    return (Role) role;
  }

  /**
   * Adds a new user with the given name to the AuthorizationPolicy.
   * If a user with the same name already exists it will be overwritten.
   */
  public User addUser(String userName) {
    Principal user = addPrincipal(userName, new HashSet<>(),
        TPrincipalType.USER);
    Preconditions.checkState(user instanceof User);
    return (User) user;
  }

  /**
   * Add a user to the catalog if it doesn't exist. This is necessary so privileges
   * can be added for a user. example: owner privileges.
   */
  public User addUserIfNotExists(String owner, Reference<Boolean> existingUser) {
    versionLock_.writeLock().lock();
    try {
      User user = getAuthPolicy().getUser(owner);
      existingUser.setRef(Boolean.TRUE);
      if (user == null) {
        user = addUser(owner);
        existingUser.setRef(Boolean.FALSE);
      }
      return user;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  private Principal addPrincipal(String principalName, Set<String> grantGroups,
      TPrincipalType type) {
    versionLock_.writeLock().lock();
    try {
      Principal principal = Principal.newInstance(principalName, type, grantGroups);
      principal.setCatalogVersion(incrementAndGetCatalogVersion());
      authPolicy_.addPrincipal(principal);
      return principal;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Removes the role with the given name from the AuthorizationPolicy. Returns the
   * removed role with an incremented catalog version, or null if no role with this name
   * exists.
   */
  public Role removeRole(String roleName) {
    Principal role = removePrincipal(roleName, TPrincipalType.ROLE);
    if (role == null) return null;
    Preconditions.checkState(role instanceof Role);
    return (Role) role;
  }

  /**
   * Removes the user with the given name from the AuthorizationPolicy. Returns the
   * removed user with an incremented catalog version, or null if no user with this name
   * exists.
   */
  public User removeUser(String userName) {
    Principal user = removePrincipal(userName, TPrincipalType.USER);
    if (user == null) return null;
    Preconditions.checkState(user instanceof User);
    return (User) user;
  }

  private Principal removePrincipal(String principalName, TPrincipalType type) {
    versionLock_.writeLock().lock();
    try {
      Principal principal = authPolicy_.removePrincipal(principalName, type);
      // TODO(todd): does this end up leaking the privileges associated
      // with this principal into the CatalogObjectVersionSet on the catalogd?
      if (principal == null) return null;
      for (PrincipalPrivilege priv: principal.getPrivileges()) {
        priv.setCatalogVersion(incrementAndGetCatalogVersion());
        deleteLog_.addRemovedObject(priv.toTCatalogObject());
      }
      principal.setCatalogVersion(incrementAndGetCatalogVersion());
      deleteLog_.addRemovedObject(principal.toTCatalogObject());
      return principal;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Adds a grant group to the given role name and returns the modified Role with
   * an updated catalog version. If the role does not exist a CatalogException is thrown.
   */
  public Role addRoleGrantGroup(String roleName, String groupName)
      throws CatalogException {
    versionLock_.writeLock().lock();
    try {
      Role role = authPolicy_.addRoleGrantGroup(roleName, groupName);
      Preconditions.checkNotNull(role);
      role.setCatalogVersion(incrementAndGetCatalogVersion());
      return role;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Removes a grant group from the given role name and returns the modified Role with
   * an updated catalog version. If the role does not exist a CatalogException is thrown.
   */
  public Role removeRoleGrantGroup(String roleName, String groupName)
      throws CatalogException {
    versionLock_.writeLock().lock();
    try {
      Role role = authPolicy_.removeRoleGrantGroup(roleName, groupName);
      Preconditions.checkNotNull(role);
      role.setCatalogVersion(incrementAndGetCatalogVersion());
      return role;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Adds a privilege to the given role name. Returns the new PrincipalPrivilege and
   * increments the catalog version. If the parent role does not exist a CatalogException
   * is thrown.
   */
  public PrincipalPrivilege addRolePrivilege(String roleName, TPrivilege thriftPriv)
      throws CatalogException {
    Preconditions.checkArgument(thriftPriv.getPrincipal_type() == TPrincipalType.ROLE);
    return addPrincipalPrivilege(roleName, thriftPriv, TPrincipalType.ROLE);
  }

  /**
   * Adds a privilege to the given user name. Returns the new PrincipalPrivilege and
   * increments the catalog version. If the user does not exist a CatalogException is
   * thrown.
   */
  public PrincipalPrivilege addUserPrivilege(String userName, TPrivilege thriftPriv)
      throws CatalogException {
    Preconditions.checkArgument(thriftPriv.getPrincipal_type() == TPrincipalType.USER);
    return addPrincipalPrivilege(userName, thriftPriv, TPrincipalType.USER);
  }

  private PrincipalPrivilege addPrincipalPrivilege(String principalName,
      TPrivilege thriftPriv, TPrincipalType type) throws CatalogException {
    versionLock_.writeLock().lock();
    try {
      Principal principal = authPolicy_.getPrincipal(principalName, type);
      if (principal == null) {
        throw new CatalogException(String.format("%s does not exist: %s",
            Principal.toString(type), principalName));
      }
      PrincipalPrivilege priv = PrincipalPrivilege.fromThrift(thriftPriv);
      priv.setCatalogVersion(incrementAndGetCatalogVersion());
      authPolicy_.addPrivilege(priv);
      return priv;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Removes a PrincipalPrivilege from the given role name and privilege name. Returns
   * the removed PrincipalPrivilege with an incremented catalog version or null if no
   * matching privilege was found. Throws a CatalogException if no role exists with this
   * name.
   */
  public PrincipalPrivilege removeRolePrivilege(String roleName, String privilegeName)
      throws CatalogException {
    return removePrincipalPrivilege(roleName, privilegeName, TPrincipalType.ROLE);
  }

  /**
   * Removes a PrincipalPrivilege from the given user name and privilege name. Returns
   * the removed PrincipalPrivilege with an incremented catalog version or null if no
   * matching privilege was found. Throws a CatalogException if no user exists with this
   * name.
   */
  public PrincipalPrivilege removeUserPrivilege(String userName, String privilegeName)
      throws CatalogException {
    return removePrincipalPrivilege(userName, privilegeName, TPrincipalType.USER);
  }

  private PrincipalPrivilege removePrincipalPrivilege(String principalName,
      String privilegeName, TPrincipalType type) throws CatalogException {
    versionLock_.writeLock().lock();
    try {
      Principal principal = authPolicy_.getPrincipal(principalName, type);
      if (principal == null) {
        throw new CatalogException(String.format("%s does not exist: %s",
            Principal.toString(type), principalName));
      }
      PrincipalPrivilege principalPrivilege = principal.removePrivilege(privilegeName);
      if (principalPrivilege == null) return null;
      principalPrivilege.setCatalogVersion(incrementAndGetCatalogVersion());
      deleteLog_.addRemovedObject(principalPrivilege.toTCatalogObject());
      return principalPrivilege;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Gets a PrincipalPrivilege from the given principal name. Returns the privilege
   * if it exists, or null if no privilege matching the privilege spec exist.
   * Throws a CatalogException if the principal does not exist.
   */
  public PrincipalPrivilege getPrincipalPrivilege(String principalName,
      TPrivilege privSpec) throws CatalogException {
    String privilegeName = PrincipalPrivilege.buildPrivilegeName(privSpec);
    versionLock_.readLock().lock();
    try {
      Principal principal = authPolicy_.getPrincipal(principalName,
          privSpec.getPrincipal_type());
      if (principal == null) {
        throw new CatalogException(Principal.toString(privSpec.getPrincipal_type()) +
            " does not exist: " + principalName);
      }
      return principal.getPrivilege(privilegeName);
    } finally {
      versionLock_.readLock().unlock();
    }
  }

  @Override
  public AuthzCacheInvalidation getAuthzCacheInvalidation(String markerName) {
    versionLock_.readLock().lock();
    try {
      return authzCacheInvalidation_.get(markerName);
    } finally {
      versionLock_.readLock().unlock();;
    }
  }

  /**
   * Gets the {@link AuthzCacheInvalidation} for a given marker name or creates a new
   * {@link AuthzCacheInvalidation} if it does not exist and increment the catalog
   * version of {@link AuthzCacheInvalidation}. A catalog version update indicates a
   * an authorization cache invalidation notification.
   *
   * @param markerName the authorization cache invalidation marker name
   * @return the updated {@link AuthzCacheInvalidation} instance
   */
  public AuthzCacheInvalidation incrementAuthzCacheInvalidationVersion(
      String markerName) {
    versionLock_.writeLock().lock();
    try {
      AuthzCacheInvalidation authzCacheInvalidation = getAuthzCacheInvalidation(
          markerName);
      if (authzCacheInvalidation == null) {
        authzCacheInvalidation = new AuthzCacheInvalidation(markerName);
        authzCacheInvalidation_.add(authzCacheInvalidation);
      }
      authzCacheInvalidation.setCatalogVersion(incrementAndGetCatalogVersion());
      return authzCacheInvalidation;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Increments the current Catalog version and returns the new value.
   */
  public long incrementAndGetCatalogVersion() {
    versionLock_.writeLock().lock();
    try {
      return ++catalogVersion_;
    } finally {
      versionLock_.writeLock().unlock();
    }
  }

  /**
   * Returns the current Catalog version.
   */
  public long getCatalogVersion() {
    versionLock_.readLock().lock();
    try {
      return catalogVersion_;
    } finally {
      versionLock_.readLock().unlock();
    }
  }

  public ReentrantReadWriteLock getLock() { return versionLock_; }
  public AuthorizationPolicy getAuthPolicy() { return authPolicy_; }

  /**
   * Reloads metadata for the partition defined by the partition spec
   * 'partitionSpec' in table 'tbl'. Returns the resulting table's TCatalogObject after
   * the partition metadata was reloaded.
   */
  public TCatalogObject reloadPartition(Table tbl,
      List<TPartitionKeyValue> partitionSpec,
      Reference<Boolean> wasPartitionReloaded, String reason) throws CatalogException {
    if (!tryLockTable(tbl)) {
      throw new CatalogException(String.format("Error reloading partition of table %s " +
          "due to lock contention", tbl.getFullName()));
    }
    try {
      long newCatalogVersion = incrementAndGetCatalogVersion();
      versionLock_.writeLock().unlock();
      HdfsTable hdfsTable = (HdfsTable) tbl;
      wasPartitionReloaded.setRef(false);
      HdfsPartition hdfsPartition = hdfsTable
          .getPartitionFromThriftPartitionSpec(partitionSpec);
      // Retrieve partition name from existing partition or construct it from
      // the partition spec
      String partitionName = hdfsPartition == null
          ? HdfsTable.constructPartitionName(partitionSpec)
          : hdfsPartition.getPartitionName();
      LOG.info(String.format("Refreshing partition metadata: %s %s (%s)",
          hdfsTable.getFullName(), partitionName, reason));
      try (MetaStoreClient msClient = getMetaStoreClient()) {
        org.apache.hadoop.hive.metastore.api.Partition hmsPartition = null;
        try {
          hmsPartition = msClient.getHiveClient().getPartition(
              hdfsTable.getDb().getName(), hdfsTable.getName(), partitionName);
        } catch (NoSuchObjectException e) {
          // If partition does not exist in Hive Metastore, remove it from the
          // catalog
          if (hdfsPartition != null) {
            hdfsTable.dropPartition(partitionSpec);
            hdfsTable.setCatalogVersion(newCatalogVersion);
            // non-existing partition was dropped from catalog, so we mark it as refreshed
            wasPartitionReloaded.setRef(true);
          } else {
            LOG.info(String.format("Partition metadata for %s was not refreshed since "
                    + "it does not exist in metastore anymore",
                hdfsTable.getFullName() + " " + partitionName));
          }
          return hdfsTable.toTCatalogObject();
        } catch (Exception e) {
          throw new CatalogException("Error loading metadata for partition: "
              + hdfsTable.getFullName() + " " + partitionName, e);
        }
        hdfsTable.reloadPartition(msClient.getHiveClient(), hdfsPartition, hmsPartition);
      }
      hdfsTable.setCatalogVersion(newCatalogVersion);
      wasPartitionReloaded.setRef(true);
      LOG.info(String.format("Refreshed partition metadata: %s %s",
          hdfsTable.getFullName(), partitionName));
      return hdfsTable.toTCatalogObject();
    } finally {
      Preconditions.checkState(!versionLock_.isWriteLockedByCurrentThread());
      tbl.getLock().unlock();
    }
  }

  public CatalogDeltaLog getDeleteLog() { return deleteLog_; }

  /**
   * Returns the version of the topic update that an operation using SYNC_DDL must wait
   * for in order to ensure that its result set ('result') has been broadcast to all the
   * coordinators. For operations that don't produce a result set, e.g. INVALIDATE
   * METADATA, return the version specified in 'result.version'.
   */
  public long waitForSyncDdlVersion(TCatalogUpdateResult result) throws CatalogException {
    if (!result.isSetUpdated_catalog_objects() &&
        !result.isSetRemoved_catalog_objects()) {
      return result.getVersion();
    }
    long lastSentTopicUpdate = lastSentTopicUpdate_.get();
    // Maximum number of attempts (topic updates) to find the catalog topic version that
    // an operation using SYNC_DDL must wait for.
    long maxNumAttempts = 5;
    if (result.isSetUpdated_catalog_objects()) {
      maxNumAttempts = Math.max(maxNumAttempts,
          result.getUpdated_catalog_objects().size() *
              (MAX_NUM_SKIPPED_TOPIC_UPDATES + 1));
    }
    long numAttempts = 0;
    long begin = System.currentTimeMillis();
    long versionToWaitFor = -1;
    while (versionToWaitFor == -1) {
      if (LOG.isTraceEnabled()) {
        LOG.trace("waitForSyncDdlVersion() attempt: " + numAttempts);
      }
      // Examine the topic update log to determine the latest topic update that
      // covers the added/modified/deleted objects in 'result'.
      long topicVersionForUpdates =
          getCoveringTopicUpdateVersion(result.getUpdated_catalog_objects());
      long topicVersionForDeletes =
          getCoveringTopicUpdateVersion(result.getRemoved_catalog_objects());
      if (topicVersionForUpdates == -1 || topicVersionForDeletes == -1) {
        LOG.info("Topic version for {} not found yet. Last sent topic version: {}. " +
                "Updated objects: {}, deleted objects: {}",
            topicVersionForUpdates == -1 ? "updates" : "deletes",
            lastSentTopicUpdate_.get(),
            FeCatalogUtils.debugString(result.updated_catalog_objects),
            FeCatalogUtils.debugString(result.removed_catalog_objects));
        // Wait for the next topic update.
        synchronized(topicUpdateLog_) {
          try {
            topicUpdateLog_.wait(TOPIC_UPDATE_WAIT_TIMEOUT_MS);
          } catch (InterruptedException e) {
            // Ignore
          }
        }
        long currentTopicUpdate = lastSentTopicUpdate_.get();
        // Don't count time-based exits from the wait() toward the maxNumAttempts
        // threshold.
        if (lastSentTopicUpdate != currentTopicUpdate) {
          ++numAttempts;
          if (numAttempts > maxNumAttempts) {
            LOG.error(String.format("Couldn't retrieve the covering topic version for "
                + "catalog objects. Updated objects: %s, deleted objects: %s",
                FeCatalogUtils.debugString(result.updated_catalog_objects),
                FeCatalogUtils.debugString(result.removed_catalog_objects)));
            throw new CatalogException("Couldn't retrieve the catalog topic version " +
                "for the SYNC_DDL operation after " + maxNumAttempts + " attempts." +
                "The operation has been successfully executed but its effects may have " +
                "not been broadcast to all the coordinators.");
          }
          lastSentTopicUpdate = currentTopicUpdate;
        }
      } else {
        versionToWaitFor = Math.max(topicVersionForDeletes, topicVersionForUpdates);
      }
    }
    Preconditions.checkState(versionToWaitFor >= 0);
    LOG.info("Operation using SYNC_DDL is waiting for catalog topic version: " +
        versionToWaitFor + ". Time to identify topic version (msec): " +
        (System.currentTimeMillis() - begin));
    return versionToWaitFor;
  }

  /**
   * Returns the version of the topic update that covers a set of TCatalogObjects.
   * A topic update U covers a TCatalogObject T, corresponding to a catalog object O,
   * if last_sent_version(O) >= catalog_version(T) && catalog_version(U) >=
   * last_topic_update(O). The first condition indicates that a version of O that is
   * larger or equal to the version in T has been added to a topic update. The second
   * condition indicates that U is either the update to include O or an update following
   * the one to include O. Returns -1 if there is a catalog object in 'tCatalogObjects'
   * which doesn't satisfy the above conditions.
   */
  private long getCoveringTopicUpdateVersion(List<TCatalogObject> tCatalogObjects) {
    if (tCatalogObjects == null || tCatalogObjects.isEmpty()) {
      return lastSentTopicUpdate_.get();
    }
    long versionToWaitFor = -1;
    for (TCatalogObject tCatalogObject: tCatalogObjects) {
      String key = Catalog.toCatalogObjectKey(tCatalogObject);
      TopicUpdateLog.Entry topicUpdateEntry = topicUpdateLog_.get(key);
      // There are two reasons for which a topic update log entry cannot be found:
      // a) It corresponds to a new catalog object that hasn't been processed by a catalog
      // update yet.
      // b) It corresponds to a catalog object that hasn't been modified for at least
      // TOPIC_UPDATE_LOG_GC_FREQUENCY updates and hence its entry was garbage
      // collected.
      // In both cases, -1 is returned to indicate that we're waiting for the
      // entry to show up in the topic update log.
      if (topicUpdateEntry == null) return -1;
      if (topicUpdateEntry.getLastSentVersion() < tCatalogObject.getCatalog_version()) {
        // TODO: This may be too verbose. Remove this after IMPALA-9135 is fixed.
        LOG.info("Should wait for next update for {}: older version {} is sent. " +
                "Expects a version >= {}.", key,
            topicUpdateEntry.getLastSentVersion(), tCatalogObject.getCatalog_version());
        return -1;
      }
      versionToWaitFor =
          Math.max(versionToWaitFor, topicUpdateEntry.getLastSentCatalogUpdate());
    }
    return versionToWaitFor;
  }

  /**
   * Retrieves information about the current catalog usage including:
   * 1. the tables with the most frequently accessed.
   * 2. the tables with the highest memory requirements.
   * 3. the tables with the highest file counts.
   * 4. the tables with the longest table loading time.
   */
  public TGetCatalogUsageResponse getCatalogUsage() {
    TGetCatalogUsageResponse usage = new TGetCatalogUsageResponse();
    usage.setLarge_tables(new ArrayList<>());
    usage.setFrequently_accessed_tables(new ArrayList<>());
    usage.setHigh_file_count_tables(new ArrayList<>());
    usage.setLong_metadata_loading_tables(new ArrayList<>());
    for (Table largeTable: CatalogUsageMonitor.INSTANCE.getLargestTables()) {
      TTableUsageMetrics tableUsageMetrics =
          new TTableUsageMetrics(largeTable.getTableName().toThrift());
      tableUsageMetrics.setMemory_estimate_bytes(largeTable.getEstimatedMetadataSize());
      usage.addToLarge_tables(tableUsageMetrics);
    }
    for (Table frequentTable:
        CatalogUsageMonitor.INSTANCE.getFrequentlyAccessedTables()) {
      TTableUsageMetrics tableUsageMetrics =
          new TTableUsageMetrics(frequentTable.getTableName().toThrift());
      tableUsageMetrics.setNum_metadata_operations(frequentTable.getMetadataOpsCount());
      usage.addToFrequently_accessed_tables(tableUsageMetrics);
    }
    for (Table mostFilesTable:
        CatalogUsageMonitor.INSTANCE.getHighFileCountTables()) {
      TTableUsageMetrics tableUsageMetrics =
          new TTableUsageMetrics(mostFilesTable.getTableName().toThrift());
      tableUsageMetrics.setNum_files(mostFilesTable.getNumFiles());
      usage.addToHigh_file_count_tables(tableUsageMetrics);
    }
    for (Table longestLoadingTable:
        CatalogUsageMonitor.INSTANCE.getLongMetadataLoadingTables()) {
      TTableUsageMetrics tableUsageMetrics =
          new TTableUsageMetrics(longestLoadingTable.getTableName().toThrift());
      tableUsageMetrics.setMedian_table_loading_ns(
          longestLoadingTable.getMedianTableLoadingTime());
      tableUsageMetrics.setMax_table_loading_ns(
          longestLoadingTable.getMaxTableLoadingTime());
      tableUsageMetrics.setP75_loading_time_ns(
          longestLoadingTable.get75TableLoadingTime());
      tableUsageMetrics.setP95_loading_time_ns(
          longestLoadingTable.get95TableLoadingTime());
      tableUsageMetrics.setP99_loading_time_ns(
          longestLoadingTable.get99TableLoadingTime());
      tableUsageMetrics.setNum_table_loading(
          longestLoadingTable.getTableLoadingCounts());
      usage.addToLong_metadata_loading_tables(tableUsageMetrics);
    }
    return usage;
  }

  /**
   * Gets the events processor metrics. Used for publishing metrics on the webUI
   */
  public TEventProcessorMetrics getEventProcessorMetrics() {
    return metastoreEventProcessor_.getEventProcessorMetrics();
  }

  /**
   * Gets the events processor summary. Used for populating the contents of the events
   * processor detailed view page
   */
  public TEventProcessorMetricsSummaryResponse getEventProcessorSummary() {
    return metastoreEventProcessor_.getEventProcessorSummary();
  }

  /**
   * Retrieves the stored metrics of the specified table and returns a pretty-printed
   * string representation. Throws an exception if table metrics were not available
   * because the table was not loaded or because another concurrent operation was holding
   * the table lock.
   */
  public String getTableMetrics(TTableName tTableName) throws CatalogException {
    String dbName = tTableName.db_name;
    String tblName = tTableName.table_name;
    Table tbl = getTable(dbName, tblName);
    if (tbl == null) {
      throw new CatalogException("Table " + dbName + "." + tblName + " was not found.");
    }
    String result;
    if (tbl instanceof IncompleteTable) {
      result = "No metrics available for table " + dbName + "." + tblName +
          ". Table not yet loaded.";
      return result;
    }
    if (!tbl.getLock().tryLock()) {
      result = "Metrics for table " + dbName + "." + tblName + "are not available " +
          "because the table is currently modified by another operation.";
      return result;
    }
    try {
      return tbl.getMetrics().toString();
    } finally {
      tbl.getLock().unlock();
    }
  }

  /**
   * A wrapper around doGetPartialCatalogObject() that controls the number of concurrent
   * invocations.
   */
  public TGetPartialCatalogObjectResponse getPartialCatalogObject(
      TGetPartialCatalogObjectRequest req) throws CatalogException {
    try {
      if (!partialObjectFetchAccess_.tryAcquire(1,
          PARTIAL_FETCH_RPC_QUEUE_TIMEOUT_S, TimeUnit.SECONDS)) {
        // Timed out trying to acquire the semaphore permit.
        throw new CatalogException("Timed out while fetching partial object metadata. " +
            "Please check the metric 'catalog.partial-fetch-rpc.queue-len' for the " +
            "current queue length and consider increasing " +
            "'catalog_partial_fetch_rpc_queue_timeout_s' and/or " +
            "'catalog_max_parallel_partial_fetch_rpc'");
      }
      // Acquired the permit at this point, should be released before we exit out of
      // this method.
      //
      // Is there a chance that this thread can get interrupted at this point before it
      // enters the try block, eventually leading to the semaphore permit not
      // getting released? It can probably happen if the JVM is already in a bad shape.
      // In the worst case, every permit is blocked and the subsequent requests throw
      // the timeout exception and the user can monitor the queue metric to see that it
      // is full, so the issue should be easy to diagnose.
      // TODO: Figure out if such a race is possible.
      try (ThreadNameAnnotator tna = new ThreadNameAnnotator(
            "Get Partial Catalog Object - " +
            Catalog.toCatalogObjectKey(req.object_desc))) {
        return doGetPartialCatalogObject(req);
      } finally {
        partialObjectFetchAccess_.release();
      }
    } catch (InterruptedException e) {
      throw new CatalogException("Error running getPartialCatalogObject(): ", e);
    }
  }

  /**
   * Gets the id for this catalog service
   */
  public String getCatalogServiceId() {
    return TUniqueIdUtil.PrintId(catalogServiceId_).intern();
  }

  /**
   * Returns the number of currently running partial RPCs.
   */
  @VisibleForTesting
  public int getConcurrentPartialRpcReqCount() {
    // Calculated based on number of currently available semaphore permits.
    return MAX_PARALLEL_PARTIAL_FETCH_RPC_COUNT - partialObjectFetchAccess_
        .availablePermits();
  }

  /**
   * Return a partial view of information about a given catalog object. This services
   * the CatalogdMetaProvider running on impalads when they are configured in
   * "local-catalog" mode. If required objects are not present, for example, the database
   * from which a table is requested, the types of the missing objects will be set in the
   * response's lookup_status.
   */
  private TGetPartialCatalogObjectResponse doGetPartialCatalogObject(
      TGetPartialCatalogObjectRequest req) throws CatalogException {
    TCatalogObject objectDesc = Preconditions.checkNotNull(req.object_desc,
        "missing object_desc");
    switch (objectDesc.type) {
    case CATALOG:
      return getPartialCatalogInfo(req);
    case DATABASE:
      TDatabase dbDesc = Preconditions.checkNotNull(req.object_desc.db);
      versionLock_.readLock().lock();
      try {
        Db db = getDb(dbDesc.getDb_name());
        if (db == null) {
          return createGetPartialCatalogObjectError(CatalogLookupStatus.DB_NOT_FOUND);
        }

        return db.getPartialInfo(req);
      } finally {
        versionLock_.readLock().unlock();
      }
    case TABLE:
    case VIEW: {
      Table table;
      try {
        table = getOrLoadTable(
            objectDesc.getTable().getDb_name(), objectDesc.getTable().getTbl_name(),
            "needed by coordinator");
      } catch (DatabaseNotFoundException e) {
        return createGetPartialCatalogObjectError(CatalogLookupStatus.DB_NOT_FOUND);
      }
      if (table == null) {
        return createGetPartialCatalogObjectError(CatalogLookupStatus.TABLE_NOT_FOUND);
      } else if (!table.isLoaded()) {
        // Table can still remain in an incomplete state if there was a concurrent
        // invalidate request.
        return createGetPartialCatalogObjectError(CatalogLookupStatus.TABLE_NOT_LOADED);
      }
      // TODO(todd): consider a read-write lock here.
      table.getLock().lock();
      try {
        return table.getPartialInfo(req);
      } finally {
        table.getLock().unlock();
      }
    }
    case FUNCTION: {
      versionLock_.readLock().lock();
      try {
        Db db = getDb(objectDesc.fn.name.db_name);
        if (db == null) {
          return createGetPartialCatalogObjectError(CatalogLookupStatus.DB_NOT_FOUND);
        }

        List<Function> funcs = db.getFunctions(objectDesc.fn.name.function_name);
        if (funcs.isEmpty()) {
          return createGetPartialCatalogObjectError(
              CatalogLookupStatus.FUNCTION_NOT_FOUND);
        }
        TGetPartialCatalogObjectResponse resp = new TGetPartialCatalogObjectResponse();
        List<TFunction> thriftFuncs = Lists.newArrayListWithCapacity(funcs.size());
        for (Function f : funcs) thriftFuncs.add(f.toThrift());
        resp.setFunctions(thriftFuncs);
        return resp;
      } finally {
        versionLock_.readLock().unlock();
      }
    }
    default:
      throw new CatalogException("Unable to fetch partial info for type: " +
          req.object_desc.type);
    }
  }

  private static TGetPartialCatalogObjectResponse createGetPartialCatalogObjectError(
      CatalogLookupStatus status) {
    TGetPartialCatalogObjectResponse resp = new TGetPartialCatalogObjectResponse();
    resp.setLookup_status(status);
    return resp;
  }

  /**
   * Return a partial view of information about global parts of the catalog (eg
   * the list of tables, etc).
   */
  private TGetPartialCatalogObjectResponse getPartialCatalogInfo(
      TGetPartialCatalogObjectRequest req) {
    TGetPartialCatalogObjectResponse resp = new TGetPartialCatalogObjectResponse();
    resp.catalog_info = new TPartialCatalogInfo();
    TCatalogInfoSelector sel = Preconditions.checkNotNull(req.catalog_info_selector,
        "no catalog_info_selector in request");
    if (sel.want_db_names) {
      resp.catalog_info.db_names = ImmutableList.copyOf(dbCache_.get().keySet());
    }
    // TODO(todd) implement data sources and other global information.
    return resp;
  }

  /**
   * Set the last used time of specified tables to now.
   * TODO: Make use of TTableUsage.num_usages.
   */
  public void updateTableUsage(TUpdateTableUsageRequest req) {
    for (TTableUsage usage : req.usages) {
      Table table = null;
      try {
        table = getTable(usage.table_name.db_name, usage.table_name.table_name);
      } catch (DatabaseNotFoundException e) {
        // do nothing
      }
      if (table != null) table.refreshLastUsedTime();
    }
  }

  CatalogdTableInvalidator getCatalogdTableInvalidator() {
    return catalogdTableInvalidator_;
  }

  @VisibleForTesting
  void setCatalogdTableInvalidator(CatalogdTableInvalidator cleaner) {
    catalogdTableInvalidator_ = cleaner;
  }

  @VisibleForTesting
  public void setMetastoreEventProcessor(
      ExternalEventsProcessor metastoreEventProcessor) {
    this.metastoreEventProcessor_ = metastoreEventProcessor;
  }
}