/*
 * Licensed 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 com.facebook.presto.hive.metastore;

import com.facebook.presto.hadoop.HadoopFileStatus;
import com.facebook.presto.hive.HdfsEnvironment;
import com.facebook.presto.hive.HdfsEnvironment.HdfsContext;
import com.facebook.presto.hive.HiveType;
import com.facebook.presto.hive.PartitionNotFoundException;
import com.facebook.presto.hive.TableAlreadyExistsException;
import com.facebook.presto.spi.ConnectorSession;
import com.facebook.presto.spi.PrestoException;
import com.facebook.presto.spi.SchemaTableName;
import com.facebook.presto.spi.StandardErrorCode;
import com.facebook.presto.spi.TableNotFoundException;
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import io.airlift.concurrent.MoreFutures;
import io.airlift.log.Logger;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;

import javax.annotation.concurrent.GuardedBy;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.Executor;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.stream.Collectors;

import static com.facebook.presto.hive.HiveErrorCode.HIVE_FILESYSTEM_ERROR;
import static com.facebook.presto.hive.HiveErrorCode.HIVE_METASTORE_ERROR;
import static com.facebook.presto.hive.HiveErrorCode.HIVE_PATH_ALREADY_EXISTS;
import static com.facebook.presto.hive.HiveMetadata.PRESTO_QUERY_ID_NAME;
import static com.facebook.presto.hive.HiveUtil.toPartitionValues;
import static com.facebook.presto.hive.HiveWriteUtils.createDirectory;
import static com.facebook.presto.hive.HiveWriteUtils.pathExists;
import static com.facebook.presto.hive.metastore.HivePrivilegeInfo.HivePrivilege.OWNERSHIP;
import static com.facebook.presto.spi.StandardErrorCode.ALREADY_EXISTS;
import static com.facebook.presto.spi.StandardErrorCode.NOT_SUPPORTED;
import static com.facebook.presto.spi.StandardErrorCode.TRANSACTION_CONFLICT;
import static com.google.common.base.MoreObjects.toStringHelper;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkState;
import static com.google.common.base.Verify.verify;
import static java.lang.String.format;
import static java.util.Objects.requireNonNull;
import static org.apache.hadoop.hive.common.FileUtils.makePartName;
import static org.apache.hadoop.hive.metastore.TableType.MANAGED_TABLE;

public class SemiTransactionalHiveMetastore
{
    private static final Logger log = Logger.get(SemiTransactionalHiveMetastore.class);
    private static final int PARTITION_COMMIT_BATCH_SIZE = 8;

    private final ExtendedHiveMetastore delegate;
    private final HdfsEnvironment hdfsEnvironment;
    private final Executor renameExecutor;
    private final boolean skipDeletionForAlter;

    @GuardedBy("this")
    private final Map<SchemaTableName, Action<TableAndMore>> tableActions = new HashMap<>();
    @GuardedBy("this")
    private final Map<SchemaTableName, Map<List<String>, Action<PartitionAndMore>>> partitionActions = new HashMap<>();
    @GuardedBy("this")
    private final List<DeclaredIntentionToWrite> declaredIntentionsToWrite = new ArrayList<>();
    @GuardedBy("this")
    private ExclusiveOperation bufferedExclusiveOperation;
    @GuardedBy("this")
    private State state = State.EMPTY;
    private boolean throwOnCleanupFailure = false;

    public SemiTransactionalHiveMetastore(HdfsEnvironment hdfsEnvironment, ExtendedHiveMetastore delegate, Executor renameExecutor, boolean skipDeletionForAlter)
    {
        this.hdfsEnvironment = requireNonNull(hdfsEnvironment, "hdfsEnvironment is null");
        this.delegate = requireNonNull(delegate, "delegate is null");
        this.renameExecutor = requireNonNull(renameExecutor, "renameExecutor is null");
        this.skipDeletionForAlter = requireNonNull(skipDeletionForAlter, "skipDeletionForAlter is null");
    }

    public synchronized List<String> getAllDatabases()
    {
        checkReadable();
        return delegate.getAllDatabases();
    }

    public synchronized Optional<Database> getDatabase(String databaseName)
    {
        checkReadable();
        return delegate.getDatabase(databaseName);
    }

    public synchronized Optional<List<String>> getAllTables(String databaseName)
    {
        checkReadable();
        if (!tableActions.isEmpty()) {
            throw new UnsupportedOperationException("Listing all tables after adding/dropping/altering tables/views in a transaction is not supported");
        }
        return delegate.getAllTables(databaseName);
    }

    public synchronized Optional<Table> getTable(String databaseName, String tableName)
    {
        checkReadable();
        Action<TableAndMore> tableAction = tableActions.get(new SchemaTableName(databaseName, tableName));
        if (tableAction == null) {
            return delegate.getTable(databaseName, tableName);
        }
        switch (tableAction.getType()) {
            case ADD:
            case ALTER:
            case INSERT_EXISTING:
                return Optional.of(tableAction.getData().getTable());
            case DROP:
                return Optional.empty();
            default:
                throw new IllegalStateException("Unknown action type");
        }
    }

    public synchronized Optional<Map<String, HiveColumnStatistics>> getTableColumnStatistics(String databaseName, String tableName, Set<String> columnNames)
    {
        checkReadable();
        Action<TableAndMore> tableAction = tableActions.get(new SchemaTableName(databaseName, tableName));
        if (tableAction == null) {
            return delegate.getTableColumnStatistics(databaseName, tableName, columnNames);
        }
        switch (tableAction.getType()) {
            case ADD:
            case ALTER:
            case INSERT_EXISTING:
            case DROP:
                return Optional.empty();
            default:
                throw new IllegalStateException("Unknown action type");
        }
    }

    public synchronized Optional<Map<String, Map<String, HiveColumnStatistics>>> getPartitionColumnStatistics(String databaseName, String tableName, Set<String> partitionNames, Set<String> columnNames)
    {
        checkReadable();
        Optional<Table> table = getTable(databaseName, tableName);
        if (!table.isPresent()) {
            return Optional.empty();
        }
        TableSource tableSource = getTableSource(databaseName, tableName);
        Map<List<String>, Action<PartitionAndMore>> partitionActionsOfTable = partitionActions.computeIfAbsent(new SchemaTableName(databaseName, tableName), k -> new HashMap<>());
        ImmutableSet.Builder<String> partitionNamesToQuery = ImmutableSet.builder();
        ImmutableMap.Builder<String, Map<String, HiveColumnStatistics>> resultBuilder = ImmutableMap.builder();
        for (String partitionName : partitionNames) {
            List<String> partitionValues = toPartitionValues(partitionName);
            Action<PartitionAndMore> partitionAction = partitionActionsOfTable.get(partitionValues);
            if (partitionAction == null) {
                switch (tableSource) {
                    case PRE_EXISTING_TABLE:
                        partitionNamesToQuery.add(partitionName);
                        break;
                    case CREATED_IN_THIS_TRANSACTION:
                        resultBuilder.put(partitionName, ImmutableMap.of());
                        break;
                    default:
                        throw new UnsupportedOperationException("unknown table source");
                }
            }
            else {
                resultBuilder.put(partitionName, ImmutableMap.of());
            }
        }

        Optional<Map<String, Map<String, HiveColumnStatistics>>> delegateResult = delegate.getPartitionColumnStatistics(databaseName, tableName, partitionNamesToQuery.build(), columnNames);
        if (delegateResult.isPresent()) {
            resultBuilder.putAll(delegateResult.get());
        }
        else {
            partitionNamesToQuery.build().forEach(partionName -> resultBuilder.put(partionName, ImmutableMap.of()));
        }
        return Optional.of(resultBuilder.build());
    }

    /**
     * This method can only be called when the table is known to exist
     */
    @GuardedBy("this")
    private TableSource getTableSource(String databaseName, String tableName)
    {
        checkHoldsLock();

        checkReadable();
        Action<TableAndMore> tableAction = tableActions.get(new SchemaTableName(databaseName, tableName));
        if (tableAction == null) {
            return TableSource.PRE_EXISTING_TABLE;
        }
        switch (tableAction.getType()) {
            case ADD:
                return TableSource.CREATED_IN_THIS_TRANSACTION;
            case ALTER:
                throw new IllegalStateException("Tables are never altered in the current implementation");
            case DROP:
                throw new TableNotFoundException(new SchemaTableName(databaseName, tableName));
            case INSERT_EXISTING:
                return TableSource.PRE_EXISTING_TABLE;
            default:
                throw new IllegalStateException("Unknown action type");
        }
    }

    public synchronized HivePageSinkMetadata generatePageSinkMetadata(SchemaTableName schemaTableName)
    {
        checkReadable();
        Optional<Table> table = getTable(schemaTableName.getSchemaName(), schemaTableName.getTableName());
        if (!table.isPresent()) {
            return new HivePageSinkMetadata(schemaTableName, Optional.empty(), ImmutableMap.of());
        }
        Map<List<String>, Action<PartitionAndMore>> partitionActionMap = partitionActions.get(schemaTableName);
        Map<List<String>, Optional<Partition>> modifiedPartitionMap;
        if (partitionActionMap == null) {
            modifiedPartitionMap = ImmutableMap.of();
        }
        else {
            ImmutableMap.Builder<List<String>, Optional<Partition>> modifiedPartitionMapBuilder = ImmutableMap.builder();
            for (Map.Entry<List<String>, Action<PartitionAndMore>> entry : partitionActionMap.entrySet()) {
                modifiedPartitionMapBuilder.put(entry.getKey(), getPartitionFromPartitionAction(entry.getValue()));
            }
            modifiedPartitionMap = modifiedPartitionMapBuilder.build();
        }
        return new HivePageSinkMetadata(
                schemaTableName,
                table,
                modifiedPartitionMap);
    }

    public synchronized Optional<List<String>> getAllViews(String databaseName)
    {
        checkReadable();
        if (!tableActions.isEmpty()) {
            throw new UnsupportedOperationException("Listing all tables after adding/dropping/altering tables/views in a transaction is not supported");
        }
        return delegate.getAllViews(databaseName);
    }

    public synchronized void createDatabase(Database database)
    {
        setExclusive((delegate, hdfsEnvironment) -> delegate.createDatabase(database));
    }

    public synchronized void dropDatabase(String schemaName)
    {
        setExclusive((delegate, hdfsEnvironment) -> delegate.dropDatabase(schemaName));
    }

    public synchronized void renameDatabase(String source, String target)
    {
        setExclusive((delegate, hdfsEnvironment) -> delegate.renameDatabase(source, target));
    }

    /**
     * {@code currentLocation} needs to be supplied if a writePath exists for the table.
     */
    public synchronized void createTable(ConnectorSession session, Table table, PrincipalPrivileges principalPrivileges, Optional<Path> currentPath)
    {
        setShared();
        // When creating a table, it should never have partition actions. This is just a sanity check.
        checkNoPartitionAction(table.getDatabaseName(), table.getTableName());
        SchemaTableName schemaTableName = new SchemaTableName(table.getDatabaseName(), table.getTableName());
        Action<TableAndMore> oldTableAction = tableActions.get(schemaTableName);
        TableAndMore tableAndMore = new TableAndMore(table, Optional.of(principalPrivileges), currentPath, Optional.empty());
        if (oldTableAction == null) {
            HdfsContext context = new HdfsContext(session, table.getDatabaseName(), table.getTableName());
            tableActions.put(schemaTableName, new Action<>(ActionType.ADD, tableAndMore, context));
            return;
        }
        switch (oldTableAction.getType()) {
            case DROP:
                throw new PrestoException(TRANSACTION_CONFLICT, "Dropping and then recreating the same table in a transaction is not supported");
            case ADD:
            case ALTER:
            case INSERT_EXISTING:
                throw new TableAlreadyExistsException(schemaTableName);
            default:
                throw new IllegalStateException("Unknown action type");
        }
    }

    public synchronized void dropTable(ConnectorSession session, String databaseName, String tableName)
    {
        setShared();
        // Dropping table with partition actions requires cleaning up staging data, which is not implemented yet.
        checkNoPartitionAction(databaseName, tableName);
        SchemaTableName schemaTableName = new SchemaTableName(databaseName, tableName);
        Action<TableAndMore> oldTableAction = tableActions.get(schemaTableName);
        if (oldTableAction == null || oldTableAction.getType() == ActionType.ALTER) {
            HdfsContext context = new HdfsContext(session, databaseName, tableName);
            tableActions.put(schemaTableName, new Action<>(ActionType.DROP, null, context));
            return;
        }
        switch (oldTableAction.getType()) {
            case DROP:
                throw new TableNotFoundException(schemaTableName);
            case ADD:
            case ALTER:
            case INSERT_EXISTING:
                throw new UnsupportedOperationException("dropping a table added/modified in the same transaction is not supported");
            default:
                throw new IllegalStateException("Unknown action type");
        }
    }

    public synchronized void replaceView(String databaseName, String tableName, Table table, PrincipalPrivileges principalPrivileges)
    {
        setExclusive((delegate, hdfsEnvironment) -> delegate.replaceTable(databaseName, tableName, table, principalPrivileges));
    }

    public synchronized void renameTable(String databaseName, String tableName, String newDatabaseName, String newTableName)
    {
        setExclusive((delegate, hdfsEnvironment) -> delegate.renameTable(databaseName, tableName, newDatabaseName, newTableName));
    }

    public synchronized void addColumn(String databaseName, String tableName, String columnName, HiveType columnType, String columnComment)
    {
        setExclusive((delegate, hdfsEnvironment) -> delegate.addColumn(databaseName, tableName, columnName, columnType, columnComment));
    }

    public synchronized void renameColumn(String databaseName, String tableName, String oldColumnName, String newColumnName)
    {
        setExclusive((delegate, hdfsEnvironment) -> delegate.renameColumn(databaseName, tableName, oldColumnName, newColumnName));
    }

    public synchronized void dropColumn(String databaseName, String tableName, String columnName)
    {
        setExclusive((delegate, hdfsEnvironment) -> delegate.dropColumn(databaseName, tableName, columnName));
    }

    public synchronized void finishInsertIntoExistingTable(ConnectorSession session, String databaseName, String tableName, Path currentLocation, List<String> fileNames)
    {
        // Data can only be inserted into partitions and unpartitioned tables. They can never be inserted into a partitioned table.
        // Therefore, this method assumes that the table is unpartitioned.
        setShared();
        SchemaTableName schemaTableName = new SchemaTableName(databaseName, tableName);
        Action<TableAndMore> oldTableAction = tableActions.get(schemaTableName);
        if (oldTableAction == null) {
            Optional<Table> table = delegate.getTable(databaseName, tableName);
            if (!table.isPresent()) {
                throw new TableNotFoundException(schemaTableName);
            }
            HdfsContext context = new HdfsContext(session, databaseName, tableName);
            tableActions.put(
                    schemaTableName,
                    new Action<>(
                            ActionType.INSERT_EXISTING,
                            new TableAndMore(table.get(), Optional.empty(), Optional.of(currentLocation), Optional.of(fileNames)), context));
            return;
        }

        switch (oldTableAction.getType()) {
            case DROP:
                throw new TableNotFoundException(schemaTableName);
            case ADD:
            case ALTER:
            case INSERT_EXISTING:
                throw new UnsupportedOperationException("Inserting into an unpartitioned table that were added, altered, or inserted into in the same transaction is not supported");
            default:
                throw new IllegalStateException("Unknown action type");
        }
    }

    public synchronized void truncateUnpartitionedTable(ConnectorSession session, String databaseName, String tableName)
    {
        checkReadable();
        Optional<Table> table = getTable(databaseName, tableName);
        SchemaTableName schemaTableName = new SchemaTableName(databaseName, tableName);
        if (!table.isPresent()) {
            throw new TableNotFoundException(schemaTableName);
        }
        if (!table.get().getTableType().equals(MANAGED_TABLE.toString())) {
            throw new PrestoException(NOT_SUPPORTED, "Cannot delete from non-managed Hive table");
        }
        if (!table.get().getPartitionColumns().isEmpty()) {
            throw new IllegalArgumentException("Table is partitioned");
        }

        Path path = new Path(table.get().getStorage().getLocation());
        HdfsContext context = new HdfsContext(session, databaseName, tableName);
        setExclusive((delegate, hdfsEnvironment) -> {
            RecursiveDeleteResult recursiveDeleteResult = recursiveDeleteFiles(hdfsEnvironment, context, path, ImmutableList.of(""), false);
            if (!recursiveDeleteResult.getNotDeletedEligibleItems().isEmpty()) {
                throw new PrestoException(HIVE_FILESYSTEM_ERROR, format(
                        "Error deleting from unpartitioned table %s. These items can not be deleted: %s",
                        schemaTableName,
                        recursiveDeleteResult.getNotDeletedEligibleItems()));
            }
        });
    }

    public synchronized Optional<List<String>> getPartitionNames(String databaseName, String tableName)
    {
        return doGetPartitionNames(databaseName, tableName, Optional.empty());
    }

    public synchronized Optional<List<String>> getPartitionNamesByParts(String databaseName, String tableName, List<String> parts)
    {
        return doGetPartitionNames(databaseName, tableName, Optional.of(parts));
    }

    @GuardedBy("this")
    private Optional<List<String>> doGetPartitionNames(String databaseName, String tableName, Optional<List<String>> parts)
    {
        checkHoldsLock();

        checkReadable();
        Optional<Table> table = getTable(databaseName, tableName);
        if (!table.isPresent()) {
            return Optional.empty();
        }
        List<String> partitionNames;
        TableSource tableSource = getTableSource(databaseName, tableName);
        switch (tableSource) {
            case CREATED_IN_THIS_TRANSACTION:
                partitionNames = ImmutableList.of();
                break;
            case PRE_EXISTING_TABLE: {
                Optional<List<String>> partitionNameResult;
                if (parts.isPresent()) {
                    partitionNameResult = delegate.getPartitionNamesByParts(databaseName, tableName, parts.get());
                }
                else {
                    partitionNameResult = delegate.getPartitionNames(databaseName, tableName);
                }
                if (!partitionNameResult.isPresent()) {
                    throw new PrestoException(TRANSACTION_CONFLICT, "Table %s.%s was dropped by another transaction");
                }
                partitionNames = partitionNameResult.get();
                break;
            }
            default:
                throw new UnsupportedOperationException("Unknown table source");
        }
        Map<List<String>, Action<PartitionAndMore>> partitionActionsOfTable = partitionActions.computeIfAbsent(new SchemaTableName(databaseName, tableName), k -> new HashMap<>());
        ImmutableList.Builder<String> resultBuilder = ImmutableList.builder();
        // alter/remove newly-altered/dropped partitions from the results from underlying metastore
        for (String partitionName : partitionNames) {
            List<String> partitionValues = toPartitionValues(partitionName);
            Action<PartitionAndMore> partitionAction = partitionActionsOfTable.get(partitionValues);
            if (partitionAction == null) {
                resultBuilder.add(partitionName);
                continue;
            }
            switch (partitionAction.getType()) {
                case ADD:
                    throw new PrestoException(TRANSACTION_CONFLICT, format("Another transaction created partition %s in table %s.%s", partitionValues, databaseName, tableName));
                case DROP:
                    // do nothing
                    break;
                case ALTER:
                case INSERT_EXISTING:
                    resultBuilder.add(partitionName);
                    break;
                default:
                    throw new IllegalStateException("Unknown action type");
            }
        }
        // add newly-added partitions to the results from underlying metastore
        if (!partitionActionsOfTable.isEmpty()) {
            List<String> columnNames = table.get().getPartitionColumns().stream().map(Column::getName).collect(Collectors.toList());
            for (Action<PartitionAndMore> partitionAction : partitionActionsOfTable.values()) {
                if (partitionAction.getType() == ActionType.ADD) {
                    List<String> values = partitionAction.getData().getPartition().getValues();
                    if (!parts.isPresent() || partitionValuesMatch(values, parts.get())) {
                        resultBuilder.add(makePartName(columnNames, values));
                    }
                }
            }
        }
        return Optional.of(resultBuilder.build());
    }

    private static boolean partitionValuesMatch(List<String> values, List<String> pattern)
    {
        checkArgument(values.size() == pattern.size());
        for (int i = 0; i < values.size(); i++) {
            if (pattern.get(i).isEmpty()) {
                // empty string match everything
                continue;
            }
            if (values.get(i).equals(pattern.get(i))) {
                return false;
            }
        }
        return true;
    }

    public synchronized Optional<Partition> getPartition(String databaseName, String tableName, List<String> partitionValues)
    {
        checkReadable();
        TableSource tableSource = getTableSource(databaseName, tableName);
        Map<List<String>, Action<PartitionAndMore>> partitionActionsOfTable = partitionActions.computeIfAbsent(new SchemaTableName(databaseName, tableName), k -> new HashMap<>());
        Action<PartitionAndMore> partitionAction = partitionActionsOfTable.get(partitionValues);
        if (partitionAction != null) {
            return getPartitionFromPartitionAction(partitionAction);
        }
        switch (tableSource) {
            case PRE_EXISTING_TABLE:
                return delegate.getPartition(databaseName, tableName, partitionValues);
            case CREATED_IN_THIS_TRANSACTION:
                return Optional.empty();
            default:
                throw new UnsupportedOperationException("unknown table source");
        }
    }

    public synchronized Map<String, Optional<Partition>> getPartitionsByNames(String databaseName, String tableName, List<String> partitionNames)
    {
        checkReadable();
        TableSource tableSource = getTableSource(databaseName, tableName);
        Map<List<String>, Action<PartitionAndMore>> partitionActionsOfTable = partitionActions.computeIfAbsent(new SchemaTableName(databaseName, tableName), k -> new HashMap<>());
        ImmutableList.Builder<String> partitionNamesToQuery = ImmutableList.builder();
        ImmutableMap.Builder<String, Optional<Partition>> resultBuilder = ImmutableMap.builder();
        for (String partitionName : partitionNames) {
            List<String> partitionValues = toPartitionValues(partitionName);
            Action<PartitionAndMore> partitionAction = partitionActionsOfTable.get(partitionValues);
            if (partitionAction == null) {
                switch (tableSource) {
                    case PRE_EXISTING_TABLE:
                        partitionNamesToQuery.add(partitionName);
                        break;
                    case CREATED_IN_THIS_TRANSACTION:
                        resultBuilder.put(partitionName, Optional.empty());
                        break;
                    default:
                        throw new UnsupportedOperationException("unknown table source");
                }
            }
            else {
                resultBuilder.put(partitionName, getPartitionFromPartitionAction(partitionAction));
            }
        }
        Map<String, Optional<Partition>> delegateResult = delegate.getPartitionsByNames(databaseName, tableName, partitionNamesToQuery.build());
        resultBuilder.putAll(delegateResult);
        return resultBuilder.build();
    }

    private static Optional<Partition> getPartitionFromPartitionAction(Action<PartitionAndMore> partitionAction)
    {
        switch (partitionAction.getType()) {
            case ADD:
            case ALTER:
            case INSERT_EXISTING:
                return Optional.of(partitionAction.getData().getAugmentedPartitionForInTransactionRead());
            case DROP:
                return Optional.empty();
            default:
                throw new IllegalStateException("Unknown action type");
        }
    }

    public synchronized void addPartition(ConnectorSession session, String databaseName, String tableName, Partition partition, Path currentLocation)
    {
        setShared();
        checkArgument(getPrestoQueryId(partition).isPresent());
        Map<List<String>, Action<PartitionAndMore>> partitionActionsOfTable = partitionActions.computeIfAbsent(new SchemaTableName(databaseName, tableName), k -> new HashMap<>());
        Action<PartitionAndMore> oldPartitionAction = partitionActionsOfTable.get(partition.getValues());
        HdfsContext context = new HdfsContext(session, databaseName, tableName);
        if (oldPartitionAction == null) {
            partitionActionsOfTable.put(
                    partition.getValues(),
                    new Action<>(ActionType.ADD, new PartitionAndMore(partition, currentLocation, Optional.empty()), context));
            return;
        }
        switch (oldPartitionAction.getType()) {
            case DROP: {
                if (!oldPartitionAction.getContext().getIdentity().getUser().equals(session.getUser())) {
                    throw new PrestoException(TRANSACTION_CONFLICT, "Operation on the same partition with different user in the same transaction is not supported");
                }
                partitionActionsOfTable.put(
                        partition.getValues(),
                        new Action<>(ActionType.ALTER, new PartitionAndMore(partition, currentLocation, Optional.empty()), context));
                break;
            }
            case ADD:
            case ALTER:
            case INSERT_EXISTING:
                throw new PrestoException(ALREADY_EXISTS, format("Partition already exists for table '%s.%s': %s", databaseName, tableName, partition.getValues()));
            default:
                throw new IllegalStateException("Unknown action type");
        }
    }

    public synchronized void dropPartition(ConnectorSession session, String databaseName, String tableName, List<String> partitionValues)
    {
        setShared();
        Map<List<String>, Action<PartitionAndMore>> partitionActionsOfTable = partitionActions.computeIfAbsent(new SchemaTableName(databaseName, tableName), k -> new HashMap<>());
        Action<PartitionAndMore> oldPartitionAction = partitionActionsOfTable.get(partitionValues);
        if (oldPartitionAction == null) {
            HdfsContext context = new HdfsContext(session, databaseName, tableName);
            partitionActionsOfTable.put(partitionValues, new Action<>(ActionType.DROP, null, context));
            return;
        }
        switch (oldPartitionAction.getType()) {
            case DROP:
                throw new PartitionNotFoundException(new SchemaTableName(databaseName, tableName), partitionValues);
            case ADD:
            case ALTER:
            case INSERT_EXISTING:
                throw new PrestoException(
                        NOT_SUPPORTED,
                        format("dropping a partition added in the same transaction is not supported: %s %s %s", databaseName, tableName, partitionValues));
            default:
                throw new IllegalStateException("Unknown action type");
        }
    }

    public synchronized void finishInsertIntoExistingPartition(ConnectorSession session, String databaseName, String tableName, List<String> partitionValues, Path currentLocation, List<String> fileNames)
    {
        setShared();
        SchemaTableName schemaTableName = new SchemaTableName(databaseName, tableName);
        Map<List<String>, Action<PartitionAndMore>> partitionActionsOfTable = partitionActions.computeIfAbsent(schemaTableName, k -> new HashMap<>());
        Action<PartitionAndMore> oldPartitionAction = partitionActionsOfTable.get(partitionValues);
        if (oldPartitionAction == null) {
            Optional<Partition> partition = delegate.getPartition(databaseName, tableName, partitionValues);
            if (!partition.isPresent()) {
                throw new PartitionNotFoundException(schemaTableName, partitionValues);
            }
            HdfsContext context = new HdfsContext(session, databaseName, tableName);
            partitionActionsOfTable.put(
                    partitionValues,
                    new Action<>(ActionType.INSERT_EXISTING, new PartitionAndMore(partition.get(), currentLocation, Optional.of(fileNames)), context));
            return;
        }

        switch (oldPartitionAction.getType()) {
            case DROP:
                throw new PartitionNotFoundException(schemaTableName, partitionValues);
            case ADD:
            case ALTER:
            case INSERT_EXISTING:
                throw new UnsupportedOperationException("Inserting into a partition that were added, altered, or inserted into in the same transaction is not supported");
            default:
                throw new IllegalStateException("Unknown action type");
        }
    }

    public synchronized Set<String> getRoles(String user)
    {
        checkReadable();
        return delegate.getRoles(user);
    }

    public synchronized Set<HivePrivilegeInfo> getDatabasePrivileges(String user, String databaseName)
    {
        checkReadable();
        return delegate.getDatabasePrivileges(user, databaseName);
    }

    public synchronized Set<HivePrivilegeInfo> getTablePrivileges(String user, String databaseName, String tableName)
    {
        checkReadable();
        SchemaTableName schemaTableName = new SchemaTableName(databaseName, tableName);
        Action<TableAndMore> tableAction = tableActions.get(schemaTableName);
        if (tableAction == null) {
            return delegate.getTablePrivileges(user, databaseName, tableName);
        }
        switch (tableAction.getType()) {
            case ADD:
            case ALTER: {
                if (!user.equals(tableAction.getData().getTable().getOwner())) {
                    throw new PrestoException(NOT_SUPPORTED, "Cannot access a table newly created in the transaction with a different user");
                }
                Collection<HivePrivilegeInfo> privileges = tableAction.getData().getPrincipalPrivileges().getUserPrivileges().get(user);
                return ImmutableSet.<HivePrivilegeInfo>builder()
                        .addAll(privileges)
                        .add(new HivePrivilegeInfo(OWNERSHIP, true))
                        .build();
            }
            case INSERT_EXISTING:
                return delegate.getTablePrivileges(user, databaseName, tableName);
            case DROP:
                throw new TableNotFoundException(schemaTableName);
            default:
                throw new IllegalStateException("Unknown action type");
        }
    }

    public synchronized void grantTablePrivileges(String databaseName, String tableName, String grantee, Set<HivePrivilegeInfo> privileges)
    {
        setExclusive((delegate, hdfsEnvironment) -> delegate.grantTablePrivileges(databaseName, tableName, grantee, privileges));
    }

    public synchronized void revokeTablePrivileges(String databaseName, String tableName, String grantee, Set<HivePrivilegeInfo> privileges)
    {
        setExclusive((delegate, hdfsEnvironment) -> delegate.revokeTablePrivileges(databaseName, tableName, grantee, privileges));
    }

    public synchronized void declareIntentionToWrite(ConnectorSession session, WriteMode writeMode, Path stagingPathRoot, String filePrefix, SchemaTableName schemaTableName)
    {
        setShared();
        if (writeMode == WriteMode.DIRECT_TO_TARGET_EXISTING_DIRECTORY) {
            Map<List<String>, Action<PartitionAndMore>> partitionActionsOfTable = partitionActions.get(schemaTableName);
            if (partitionActionsOfTable != null && !partitionActionsOfTable.isEmpty()) {
                throw new PrestoException(NOT_SUPPORTED, "Can not insert into a table with a partition that has been modified in the same transaction when Presto is configured to skip temporary directories.");
            }
        }
        HdfsContext context = new HdfsContext(session, schemaTableName.getSchemaName(), schemaTableName.getTableName());
        declaredIntentionsToWrite.add(new DeclaredIntentionToWrite(writeMode, context, stagingPathRoot, filePrefix, schemaTableName));
    }

    public synchronized void commit()
    {
        try {
            switch (state) {
                case EMPTY:
                    break;
                case SHARED_OPERATION_BUFFERED:
                    commitShared();
                    break;
                case EXCLUSIVE_OPERATION_BUFFERED:
                    requireNonNull(bufferedExclusiveOperation, "bufferedExclusiveOperation is null");
                    bufferedExclusiveOperation.execute(delegate, hdfsEnvironment);
                    break;
                case FINISHED:
                    throw new IllegalStateException("Tried to commit buffered metastore operations after transaction has been committed/aborted");
                default:
                    throw new IllegalStateException("Unknown state");
            }
        }
        finally {
            state = State.FINISHED;
        }
    }

    public synchronized void rollback()
    {
        try {
            switch (state) {
                case EMPTY:
                case EXCLUSIVE_OPERATION_BUFFERED:
                    break;
                case SHARED_OPERATION_BUFFERED:
                    rollbackShared();
                    break;
                case FINISHED:
                    throw new IllegalStateException("Tried to rollback buffered metastore operations after transaction has been committed/aborted");
                default:
                    throw new IllegalStateException("Unknown state");
            }
        }
        finally {
            state = State.FINISHED;
        }
    }

    @GuardedBy("this")
    private void commitShared()
    {
        checkHoldsLock();

        Committer committer = new Committer();
        try {
            for (Map.Entry<SchemaTableName, Action<TableAndMore>> entry : tableActions.entrySet()) {
                SchemaTableName schemaTableName = entry.getKey();
                Action<TableAndMore> action = entry.getValue();
                switch (action.getType()) {
                    case DROP:
                        committer.prepareDropTable(schemaTableName);
                        break;
                    case ALTER:
                        committer.prepareAlterTable();
                        break;
                    case ADD:
                        committer.prepareAddTable(action.getContext(), action.getData());
                        break;
                    case INSERT_EXISTING:
                        committer.prepareInsertExistingTable(action.getContext(), action.getData());
                        break;
                    default:
                        throw new IllegalStateException("Unknown action type");
                }
            }
            for (Map.Entry<SchemaTableName, Map<List<String>, Action<PartitionAndMore>>> tableEntry : partitionActions.entrySet()) {
                SchemaTableName schemaTableName = tableEntry.getKey();
                for (Map.Entry<List<String>, Action<PartitionAndMore>> partitionEntry : tableEntry.getValue().entrySet()) {
                    List<String> partitionValues = partitionEntry.getKey();
                    Action<PartitionAndMore> action = partitionEntry.getValue();
                    switch (action.getType()) {
                        case DROP:
                            committer.prepareDropPartition(schemaTableName, partitionValues);
                            break;
                        case ALTER:
                            committer.prepareAlterPartition(action.getContext(), action.getData());
                            break;
                        case ADD:
                            committer.prepareAddPartition(action.getContext(), action.getData());
                            break;
                        case INSERT_EXISTING:
                            committer.prepareInsertExistingPartition(action.getContext(), action.getData());
                            break;
                        default:
                            throw new IllegalStateException("Unknown action type");
                    }
                }
            }

            // Wait for all renames submitted for "INSERT_EXISTING" action to finish
            committer.waitForAsyncRenames();

            // At this point, all file system operations, whether asynchronously issued or not, have completed successfully.
            // We are moving on to metastore operations now.

            committer.executeAddTableOperations();
            committer.executeAlterPartitionOperations();
            committer.executeAddPartitionOperations();
        }
        catch (Throwable t) {
            committer.cancelUnstartedAsyncRenames();

            committer.undoAddPartitionOperations();
            committer.undoAddTableOperations();

            committer.waitForAsyncRenamesSuppressThrowables();

            // fileRenameFutures must all come back before any file system cleanups are carried out.
            // Otherwise, files that should be deleted may be created after cleanup is done.
            committer.executeCleanupTasksForAbort(committer.extractFilePrefixes(declaredIntentionsToWrite));

            committer.executeRenameTasksForAbort();

            // Partition directory must be put back before relevant metastore operation can be undone
            committer.undoAlterPartitionOperations();

            rollbackShared();

            throw t;
        }

        try {
            // After this line, operations are no longer reversible.
            // The next section will deal with "dropping table/partition". Commit may still fail in
            // this section. Even if commit fails, cleanups, instead of rollbacks, will be executed.

            committer.executeIrreversibleMetastoreOperations();

            // If control flow reached this point, this commit is considered successful no matter
            // what happens later. The only kind of operations that haven't been carried out yet
            // are cleanups.

            // The program control flow will go to finally next. And cleanup will run because
            // moveForwardInFinally has been set to false.
        }
        finally {
            // In this method, all operations are best-effort clean up operations.
            // If any operation fails, the error will be logged and ignored.
            // Additionally, other clean up operations should still be attempted.

            // Execute deletion tasks
            committer.executeDeletionTasksForFinish();

            // Clean up empty staging directories (that may recursively contain empty directories)
            committer.deleteEmptyStagingDirectories(declaredIntentionsToWrite);
        }
    }

    private class Committer
    {
        private final AtomicBoolean fileRenameCancelled = new AtomicBoolean(false);
        private final List<CompletableFuture<?>> fileRenameFutures = new ArrayList<>();

        // File system
        // For file system changes, only operations outside of writing paths (as specified in declared intentions to write)
        // need to MOVE_BACKWARD tasks scheduled. Files in writing paths are handled by rollbackShared().
        private final List<DirectoryDeletionTask> deletionTasksForFinish = new ArrayList<>();
        private final List<DirectoryCleanUpTask> cleanUpTasksForAbort = new ArrayList<>();
        private final List<DirectoryRenameTask> renameTasksForAbort = new ArrayList<>();

        // Metastore
        private final List<CreateTableOperation> addTableOperations = new ArrayList<>();
        private final Map<SchemaTableName, PartitionAdder> partitionAdders = new HashMap<>();
        private final List<AlterPartitionOperation> alterPartitionOperations = new ArrayList<>();
        private final List<IrreversibleMetastoreOperation> metastoreDeleteOperations = new ArrayList<>();

        private void prepareDropTable(SchemaTableName schemaTableName)
        {
            metastoreDeleteOperations.add(new IrreversibleMetastoreOperation(
                    format("drop table %s", schemaTableName),
                    () -> delegate.dropTable(schemaTableName.getSchemaName(), schemaTableName.getTableName(), true)));
        }

        private void prepareAlterTable()
        {
            // Currently, ALTER action is never constructed for tables. Dropping a table and then re-creating it
            // in the same transaction is not supported now. The following line should be replaced with actual
            // implementation when create after drop support is introduced for a table.
            throw new UnsupportedOperationException("Dropping and then creating a table with the same name is not supported");
        }

        private void prepareAddTable(HdfsContext context, TableAndMore tableAndMore)
        {
            Table table = tableAndMore.getTable();
            if (table.getTableType().equals(MANAGED_TABLE.name())) {
                String targetLocation = table.getStorage().getLocation();
                checkArgument(!targetLocation.isEmpty(), "target location is empty");
                Optional<Path> currentPath = tableAndMore.getCurrentLocation();
                Path targetPath = new Path(targetLocation);
                if (table.getPartitionColumns().isEmpty() && currentPath.isPresent()) {
                    // CREATE TABLE AS SELECT unpartitioned table
                    if (targetPath.equals(currentPath.get())) {
                        // Target path and current path are the same. Therefore, directory move is not needed.
                    }
                    else {
                        renameDirectory(
                                context,
                                hdfsEnvironment,
                                currentPath.get(),
                                targetPath,
                                () -> cleanUpTasksForAbort.add(new DirectoryCleanUpTask(context, targetPath, true)));
                    }
                }
                else {
                    // CREATE TABLE AS SELECT partitioned table, or
                    // CREATE TABLE partitioned/unpartitioned table (without data)
                    if (pathExists(context, hdfsEnvironment, targetPath)) {
                        if (currentPath.isPresent() && currentPath.get().equals(targetPath)) {
                            // It is okay to skip directory creation when currentPath is equal to targetPath
                            // because the directory may have been created when creating partition directories.
                            // However, it is important to note that the two being equal does not guarantee
                            // a directory had been created.
                        }
                        else {
                            throw new PrestoException(
                                    HIVE_PATH_ALREADY_EXISTS,
                                    format("Unable to create directory %s: target directory already exists", targetPath));
                        }
                    }
                    else {
                        cleanUpTasksForAbort.add(new DirectoryCleanUpTask(context, targetPath, true));
                        createDirectory(context, hdfsEnvironment, targetPath);
                    }
                }
            }

            addTableOperations.add(new CreateTableOperation(table, tableAndMore.getPrincipalPrivileges()));
        }

        private void prepareInsertExistingTable(HdfsContext context, TableAndMore tableAndMore)
        {
            Table table = tableAndMore.getTable();
            Path targetPath = new Path(table.getStorage().getLocation());
            Path currentPath = tableAndMore.getCurrentLocation().get();
            cleanUpTasksForAbort.add(new DirectoryCleanUpTask(context, targetPath, false));
            if (!targetPath.equals(currentPath)) {
                asyncRename(hdfsEnvironment, renameExecutor, fileRenameCancelled, fileRenameFutures, context, currentPath, targetPath, tableAndMore.getFileNames().get());
            }
        }

        private void prepareDropPartition(SchemaTableName schemaTableName, List<String> partitionValues)
        {
            metastoreDeleteOperations.add(new IrreversibleMetastoreOperation(
                    format("drop partition %s.%s %s", schemaTableName, schemaTableName.getTableName(), partitionValues),
                    () -> delegate.dropPartition(schemaTableName.getSchemaName(), schemaTableName.getTableName(), partitionValues, true)));
        }

        private void prepareAlterPartition(HdfsContext context, PartitionAndMore partitionAndMore)
        {
            Partition partition = partitionAndMore.getPartition();
            String targetLocation = partition.getStorage().getLocation();
            Optional<Partition> oldPartition = delegate.getPartition(partition.getDatabaseName(), partition.getTableName(), partition.getValues());
            if (!oldPartition.isPresent()) {
                throw new PrestoException(
                        TRANSACTION_CONFLICT,
                        format("The partition that this transaction modified was deleted in another transaction. %s %s", partition.getTableName(), partition.getValues()));
            }
            String oldPartitionLocation = oldPartition.get().getStorage().getLocation();
            Path oldPartitionPath = new Path(oldPartitionLocation);

            // Location of the old partition and the new partition can be different because we allow arbitrary directories through LocationService.
            // If the location of the old partition is the same as the location of the new partition:
            // * Rename the old data directory to a temporary path with a special suffix
            // * Remember we will need to delete that directory at the end if transaction successfully commits
            // * Remember we will need to undo the rename if transaction aborts
            // Otherwise,
            // * Remember we will need to delete the location of the old partition at the end if transaction successfully commits
            if (targetLocation.equals(oldPartitionLocation)) {
                Path oldPartitionStagingPath = new Path(oldPartitionPath.getParent(), "_temp_" + oldPartitionPath.getName() + "_" + context.getQueryId());
                renameDirectory(
                        context,
                        hdfsEnvironment,
                        oldPartitionPath,
                        oldPartitionStagingPath,
                        () -> renameTasksForAbort.add(new DirectoryRenameTask(context, oldPartitionStagingPath, oldPartitionPath)));
                if (!skipDeletionForAlter) {
                    deletionTasksForFinish.add(new DirectoryDeletionTask(context, oldPartitionStagingPath));
                }
            }
            else {
                if (!skipDeletionForAlter) {
                    deletionTasksForFinish.add(new DirectoryDeletionTask(context, oldPartitionPath));
                }
            }

            Path currentPath = partitionAndMore.getCurrentLocation();
            Path targetPath = new Path(targetLocation);
            if (!targetPath.equals(currentPath)) {
                renameDirectory(
                        context,
                        hdfsEnvironment,
                        currentPath,
                        targetPath,
                        () -> cleanUpTasksForAbort.add(new DirectoryCleanUpTask(context, targetPath, true)));
            }
            // Partition alter must happen regardless of whether original and current location is the same
            // because metadata might change: e.g. storage format, column types, etc
            alterPartitionOperations.add(new AlterPartitionOperation(partition, oldPartition.get()));
        }

        private void prepareAddPartition(HdfsContext context, PartitionAndMore partitionAndMore)
        {
            Partition partition = partitionAndMore.getPartition();
            String targetLocation = partition.getStorage().getLocation();
            Path currentPath = partitionAndMore.getCurrentLocation();
            Path targetPath = new Path(targetLocation);

            SchemaTableName schemaTableName = new SchemaTableName(partition.getDatabaseName(), partition.getTableName());
            PartitionAdder partitionAdder = partitionAdders.computeIfAbsent(
                    schemaTableName,
                    ignored -> new PartitionAdder(partition.getDatabaseName(), partition.getTableName(), delegate, PARTITION_COMMIT_BATCH_SIZE));

            if (!targetPath.equals(currentPath)) {
                renameDirectory(
                        context,
                        hdfsEnvironment,
                        currentPath,
                        targetPath,
                        () -> cleanUpTasksForAbort.add(new DirectoryCleanUpTask(context, targetPath, true)));
            }
            partitionAdder.addPartition(partition);
        }

        private void prepareInsertExistingPartition(HdfsContext context, PartitionAndMore partitionAndMore)
        {
            Partition partition = partitionAndMore.getPartition();
            Path targetPath = new Path(partition.getStorage().getLocation());
            Path currentPath = partitionAndMore.getCurrentLocation();
            cleanUpTasksForAbort.add(new DirectoryCleanUpTask(context, targetPath, false));
            if (!targetPath.equals(currentPath)) {
                asyncRename(hdfsEnvironment, renameExecutor, fileRenameCancelled, fileRenameFutures, context, currentPath, targetPath, partitionAndMore.getFileNames());
            }
        }

        private void executeCleanupTasksForAbort(List<String> filePrefixes)
        {
            for (DirectoryCleanUpTask cleanUpTask : cleanUpTasksForAbort) {
                recursiveDeleteFilesAndLog(cleanUpTask.getContext(), cleanUpTask.getPath(), filePrefixes, cleanUpTask.isDeleteEmptyDirectory(), "temporary directory commit abort");
            }
        }

        private void executeDeletionTasksForFinish()
        {
            for (DirectoryDeletionTask deletionTask : deletionTasksForFinish) {
                if (!deleteRecursivelyIfExists(deletionTask.getContext(), hdfsEnvironment, deletionTask.getPath())) {
                    logCleanupFailure("Error deleting directory %s", deletionTask.getPath().toString());
                }
            }
        }

        private void executeRenameTasksForAbort()
        {
            for (DirectoryRenameTask directoryRenameTask : renameTasksForAbort) {
                try {
                    // Ignore the task if the source directory doesn't exist.
                    // This is probably because the original rename that we are trying to undo here never succeeded.
                    if (pathExists(directoryRenameTask.getContext(), hdfsEnvironment, directoryRenameTask.getRenameFrom())) {
                        renameDirectory(directoryRenameTask.getContext(), hdfsEnvironment, directoryRenameTask.getRenameFrom(), directoryRenameTask.getRenameTo(), () -> {});
                    }
                }
                catch (Throwable throwable) {
                    logCleanupFailure(throwable, "failed to undo rename of partition directory: %s to %s", directoryRenameTask.getRenameFrom(), directoryRenameTask.getRenameTo());
                }
            }
        }

        private void deleteEmptyStagingDirectories(List<DeclaredIntentionToWrite> declaredIntentionsToWrite)
        {
            for (DeclaredIntentionToWrite declaredIntentionToWrite : declaredIntentionsToWrite) {
                if (declaredIntentionToWrite.getMode() != WriteMode.STAGE_AND_MOVE_TO_TARGET_DIRECTORY) {
                    continue;
                }
                Path path = declaredIntentionToWrite.getRootPath();
                recursiveDeleteFilesAndLog(declaredIntentionToWrite.getContext(), path, ImmutableList.of(), true, "staging directory cleanup");
            }
        }

        private void waitForAsyncRenames()
        {
            for (CompletableFuture<?> fileRenameFuture : fileRenameFutures) {
                MoreFutures.getFutureValue(fileRenameFuture, PrestoException.class);
            }
        }

        private void waitForAsyncRenamesSuppressThrowables()
        {
            for (CompletableFuture<?> future : fileRenameFutures) {
                try {
                    future.get();
                }
                catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                }
                catch (Throwable t) {
                    // ignore
                }
            }
        }

        private void cancelUnstartedAsyncRenames()
        {
            fileRenameCancelled.set(true);
        }

        private void executeAddTableOperations()
        {
            for (CreateTableOperation addTableOperation : addTableOperations) {
                addTableOperation.run(delegate);
            }
        }

        private void executeAlterPartitionOperations()
        {
            for (AlterPartitionOperation alterPartitionOperation : alterPartitionOperations) {
                alterPartitionOperation.run(delegate);
            }
        }

        private void executeAddPartitionOperations()
        {
            for (PartitionAdder partitionAdder : partitionAdders.values()) {
                partitionAdder.execute();
            }
        }

        private void undoAddPartitionOperations()
        {
            for (PartitionAdder partitionAdder : partitionAdders.values()) {
                List<List<String>> partitionsFailedToRollback = partitionAdder.rollback();
                if (!partitionsFailedToRollback.isEmpty()) {
                    logCleanupFailure("Failed to rollback: add_partition for partitions %s.%s %s",
                            partitionAdder.getSchemaName(),
                            partitionAdder.getTableName(),
                            partitionsFailedToRollback.stream());
                }
            }
        }

        private void undoAddTableOperations()
        {
            for (CreateTableOperation addTableOperation : addTableOperations) {
                try {
                    addTableOperation.undo(delegate);
                }
                catch (Throwable throwable) {
                    logCleanupFailure(throwable, "failed to rollback: %s", addTableOperation.getDescription());
                }
            }
        }

        private void undoAlterPartitionOperations()
        {
            for (AlterPartitionOperation alterPartitionOperation : alterPartitionOperations) {
                try {
                    alterPartitionOperation.undo(delegate);
                }
                catch (Throwable throwable) {
                    logCleanupFailure(throwable, "failed to rollback: %s", alterPartitionOperation.getDescription());
                }
            }
        }

        private void executeIrreversibleMetastoreOperations()
        {
            List<String> failedIrreversibleOperationDescriptions = new ArrayList<>();
            List<Throwable> suppressedExceptions = new ArrayList<>();
            for (IrreversibleMetastoreOperation irreversibleMetastoreOperation : metastoreDeleteOperations) {
                try {
                    irreversibleMetastoreOperation.run();
                }
                catch (Throwable t) {
                    failedIrreversibleOperationDescriptions.add(irreversibleMetastoreOperation.getDescription());
                    // A limit is needed to avoid having a huge exception object. 5 was chosen arbitrarily.
                    if (suppressedExceptions.size() < 5) {
                        suppressedExceptions.add(t);
                    }
                }
            }
            if (!suppressedExceptions.isEmpty()) {
                PrestoException prestoException = new PrestoException(
                        HIVE_METASTORE_ERROR,
                        format(
                                "The transaction didn't commit cleanly. Failed to execute some metastore delete operations: %s",
                                failedIrreversibleOperationDescriptions.stream()
                                        .collect(Collectors.joining("; "))));
                suppressedExceptions.forEach(prestoException::addSuppressed);
                throw prestoException;
            }
        }

        private List<String> extractFilePrefixes(List<DeclaredIntentionToWrite> declaredIntentionsToWrite)
        {
            Set<String> filePrefixSet = new HashSet<>();
            for (DeclaredIntentionToWrite declaredIntentionToWrite : declaredIntentionsToWrite) {
                filePrefixSet.add(declaredIntentionToWrite.getFilePrefix());
            }
            return ImmutableList.copyOf(filePrefixSet);
        }
    }

    @GuardedBy("this")
    private void rollbackShared()
    {
        checkHoldsLock();

        for (DeclaredIntentionToWrite declaredIntentionToWrite : declaredIntentionsToWrite) {
            switch (declaredIntentionToWrite.getMode()) {
                case STAGE_AND_MOVE_TO_TARGET_DIRECTORY:
                case DIRECT_TO_TARGET_NEW_DIRECTORY: {
                    // Note: there is no need to cleanup the target directory as it will only be written
                    // to during the commit call and the commit call cleans up after failures.
                    Path rootPath = declaredIntentionToWrite.getRootPath();

                    // In the case of DIRECT_TO_TARGET_NEW_DIRECTORY, if the directory is not guaranteed to be unique
                    // for the query, it is possible that another query or compute engine may see the directory, wrote
                    // data to it, and exported it through metastore. Therefore it may be argued that cleanup of staging
                    // directories must be carried out conservatively. To be safe, we only delete files that start with
                    // the unique prefix for queries in this transaction.

                    recursiveDeleteFilesAndLog(
                            declaredIntentionToWrite.getContext(),
                            rootPath,
                            ImmutableList.of(declaredIntentionToWrite.getFilePrefix()),
                            true,
                            format("staging/target_new directory rollback for table %s", declaredIntentionToWrite.getSchemaTableName()));
                    break;
                }
                case DIRECT_TO_TARGET_EXISTING_DIRECTORY: {
                    Set<Path> pathsToClean = new HashSet<>();

                    // Check the base directory of the declared intention
                    // * existing partition may also be in this directory
                    // * this is where new partitions are created
                    Path baseDirectory = declaredIntentionToWrite.getRootPath();
                    pathsToClean.add(baseDirectory);

                    SchemaTableName schemaTableName = declaredIntentionToWrite.getSchemaTableName();
                    Optional<Table> table = delegate.getTable(schemaTableName.getSchemaName(), schemaTableName.getTableName());
                    if (table.isPresent()) {
                        // check every existing partition that is outside for the base directory
                        if (!table.get().getPartitionColumns().isEmpty()) {
                            List<String> partitionNames = delegate.getPartitionNames(schemaTableName.getSchemaName(), schemaTableName.getTableName())
                                    .orElse(ImmutableList.of());
                            for (List<String> partitionNameBatch : Iterables.partition(partitionNames, 10)) {
                                Collection<Optional<Partition>> partitions = delegate.getPartitionsByNames(schemaTableName.getSchemaName(), schemaTableName.getTableName(), partitionNameBatch).values();
                                partitions.stream()
                                        .filter(Optional::isPresent)
                                        .map(Optional::get)
                                        .map(partition -> partition.getStorage().getLocation())
                                        .map(Path::new)
                                        .filter(path -> !isSameOrParent(baseDirectory, path))
                                        .forEach(pathsToClean::add);
                            }
                        }
                    }
                    else {
                        logCleanupFailure(
                                "Error rolling back write to table %s.%s. Data directory may contain temporary data. Table was dropped in another transaction.",
                                schemaTableName.getSchemaName(),
                                schemaTableName.getTableName());
                    }

                    // delete any file that starts with the unique prefix of this query
                    for (Path path : pathsToClean) {
                        // TODO: It is a known deficiency that some empty directory does not get cleaned up in S3.
                        // We can not delete any of the directories here since we do not know who created them.
                        recursiveDeleteFilesAndLog(
                                declaredIntentionToWrite.getContext(),
                                path,
                                ImmutableList.of(declaredIntentionToWrite.getFilePrefix()),
                                false,
                                format("target_existing directory rollback for table %s", schemaTableName));
                    }

                    break;
                }
                default:
                    throw new UnsupportedOperationException("Unknown write mode");
            }
        }
    }

    @VisibleForTesting
    public synchronized void testOnlyCheckIsReadOnly()
    {
        if (state != State.EMPTY) {
            throw new AssertionError("Test did not commit or rollback");
        }
    }

    @VisibleForTesting
    public void testOnlyThrowOnCleanupFailures()
    {
        throwOnCleanupFailure = true;
    }

    @GuardedBy("this")
    private void checkReadable()
    {
        checkHoldsLock();

        switch (state) {
            case EMPTY:
            case SHARED_OPERATION_BUFFERED:
                return;
            case EXCLUSIVE_OPERATION_BUFFERED:
                throw new PrestoException(NOT_SUPPORTED, "Unsupported combination of operations in a single transaction");
            case FINISHED:
                throw new IllegalStateException("Tried to access metastore after transaction has been committed/aborted");
        }
    }

    @GuardedBy("this")
    private void setShared()
    {
        checkHoldsLock();

        checkReadable();
        state = State.SHARED_OPERATION_BUFFERED;
    }

    @GuardedBy("this")
    private void setExclusive(ExclusiveOperation exclusiveOperation)
    {
        checkHoldsLock();

        if (state != State.EMPTY) {
            throw new PrestoException(StandardErrorCode.NOT_SUPPORTED, "Unsupported combination of operations in a single transaction");
        }
        state = State.EXCLUSIVE_OPERATION_BUFFERED;
        bufferedExclusiveOperation = exclusiveOperation;
    }

    @GuardedBy("this")
    private void checkNoPartitionAction(String databaseName, String tableName)
    {
        checkHoldsLock();

        Map<List<String>, Action<PartitionAndMore>> partitionActionsOfTable = partitionActions.get(new SchemaTableName(databaseName, tableName));
        if (partitionActionsOfTable != null && !partitionActionsOfTable.isEmpty()) {
            throw new PrestoException(NOT_SUPPORTED, "Cannot make schema changes to a table/view with modified partitions in the same transaction");
        }
    }

    private static boolean isSameOrParent(Path parent, Path child)
    {
        int parentDepth = parent.depth();
        int childDepth = child.depth();
        if (parentDepth > childDepth) {
            return false;
        }
        for (int i = childDepth; i > parentDepth; i--) {
            child = child.getParent();
        }
        return parent.equals(child);
    }

    private void logCleanupFailure(String format, Object... args)
    {
        if (throwOnCleanupFailure) {
            throw new RuntimeException(format(format, args));
        }
        log.warn(format, args);
    }

    private void logCleanupFailure(Throwable t, String format, Object... args)
    {
        if (throwOnCleanupFailure) {
            throw new RuntimeException(format(format, args), t);
        }
        log.warn(t, format, args);
    }

    private static void asyncRename(
            HdfsEnvironment hdfsEnvironment,
            Executor executor,
            AtomicBoolean cancelled,
            List<CompletableFuture<?>> fileRenameFutures,
            HdfsContext context,
            Path currentPath,
            Path targetPath,
            List<String> fileNames)
    {
        FileSystem fileSystem;
        try {
            fileSystem = hdfsEnvironment.getFileSystem(context, currentPath);
        }
        catch (IOException e) {
            throw new PrestoException(HIVE_FILESYSTEM_ERROR, format("Error moving data files to final location. Error listing directory %s", currentPath), e);
        }

        for (String fileName : fileNames) {
            Path source = new Path(currentPath, fileName);
            Path target = new Path(targetPath, fileName);
            fileRenameFutures.add(CompletableFuture.runAsync(() -> {
                if (cancelled.get()) {
                    return;
                }
                try {
                    if (fileSystem.exists(target) || !fileSystem.rename(source, target)) {
                        throw new PrestoException(HIVE_FILESYSTEM_ERROR, format("Error moving data files from %s to final location %s", source, target));
                    }
                }
                catch (IOException e) {
                    throw new PrestoException(HIVE_FILESYSTEM_ERROR, format("Error moving data files from %s to final location %s", source, target), e);
                }
            }, executor));
        }
    }

    private void recursiveDeleteFilesAndLog(HdfsContext context, Path directory, List<String> filePrefixes, boolean deleteEmptyDirectories, String reason)
    {
        RecursiveDeleteResult recursiveDeleteResult = recursiveDeleteFiles(
                hdfsEnvironment,
                context,
                directory,
                filePrefixes,
                deleteEmptyDirectories);
        if (!recursiveDeleteResult.getNotDeletedEligibleItems().isEmpty()) {
            logCleanupFailure(
                    "Error deleting directory %s for %s. Some eligible items can not be deleted: %s.",
                    directory.toString(),
                    reason,
                    recursiveDeleteResult.getNotDeletedEligibleItems());
        }
        else if (deleteEmptyDirectories && !recursiveDeleteResult.isDirectoryNoLongerExists()) {
            logCleanupFailure(
                    "Error deleting directory %s for %s. Can not delete the directory.",
                    directory.toString(),
                    reason);
        }
    }

    /**
     * Attempt to recursively remove eligible files and/or directories in {@code directory}.
     * <p>
     * When {@code filePrefixes} is not present, all files (but not necessarily directories) will be
     * ineligible. If all files shall be deleted, you can use an empty string as {@code filePrefixes}.
     * <p>
     * When {@code deleteEmptySubDirectory} is true, any empty directory (including directories that
     * were originally empty, and directories that become empty after files prefixed with
     * {@code filePrefixes} are deleted) will be eligible.
     * <p>
     * This method will not delete anything that's neither a directory nor a file.
     *
     * @param filePrefixes prefix of files that should be deleted
     * @param deleteEmptyDirectories whether empty directories should be deleted
     */
    private static RecursiveDeleteResult recursiveDeleteFiles(HdfsEnvironment hdfsEnvironment, HdfsContext context, Path directory, List<String> filePrefixes, boolean deleteEmptyDirectories)
    {
        FileSystem fileSystem;
        try {
            fileSystem = hdfsEnvironment.getFileSystem(context, directory);

            if (!fileSystem.exists(directory)) {
                return new RecursiveDeleteResult(true, ImmutableList.of());
            }
        }
        catch (IOException e) {
            ImmutableList.Builder<String> notDeletedItems = ImmutableList.builder();
            notDeletedItems.add(directory.toString() + "/**");
            return new RecursiveDeleteResult(false, notDeletedItems.build());
        }

        return doRecursiveDeleteFiles(fileSystem, directory, filePrefixes, deleteEmptyDirectories);
    }

    private static RecursiveDeleteResult doRecursiveDeleteFiles(FileSystem fileSystem, Path directory, List<String> filePrefixes, boolean deleteEmptyDirectories)
    {
        // don't delete hidden presto directories
        if (directory.getName().startsWith(".presto")) {
            return new RecursiveDeleteResult(false, ImmutableList.of());
        }

        FileStatus[] allFiles;
        try {
            allFiles = fileSystem.listStatus(directory);
        }
        catch (IOException e) {
            ImmutableList.Builder<String> notDeletedItems = ImmutableList.builder();
            notDeletedItems.add(directory.toString() + "/**");
            return new RecursiveDeleteResult(false, notDeletedItems.build());
        }

        boolean allDescendentsDeleted = true;
        ImmutableList.Builder<String> notDeletedEligibleItems = ImmutableList.builder();
        for (FileStatus fileStatus : allFiles) {
            if (HadoopFileStatus.isFile(fileStatus)) {
                Path filePath = fileStatus.getPath();
                String fileName = filePath.getName();
                boolean eligible = false;
                // never delete presto dot files
                if (!fileName.startsWith(".presto")) {
                    eligible = filePrefixes.stream().anyMatch(fileName::startsWith);
                }
                if (eligible) {
                    if (!deleteIfExists(fileSystem, filePath, false)) {
                        allDescendentsDeleted = false;
                        notDeletedEligibleItems.add(filePath.toString());
                    }
                }
                else {
                    allDescendentsDeleted = false;
                }
            }
            else if (HadoopFileStatus.isDirectory(fileStatus)) {
                RecursiveDeleteResult subResult = doRecursiveDeleteFiles(fileSystem, fileStatus.getPath(), filePrefixes, deleteEmptyDirectories);
                if (!subResult.isDirectoryNoLongerExists()) {
                    allDescendentsDeleted = false;
                }
                if (!subResult.getNotDeletedEligibleItems().isEmpty()) {
                    notDeletedEligibleItems.addAll(subResult.getNotDeletedEligibleItems());
                }
            }
            else {
                allDescendentsDeleted = false;
                notDeletedEligibleItems.add(fileStatus.getPath().toString());
            }
        }
        if (allDescendentsDeleted && deleteEmptyDirectories) {
            verify(notDeletedEligibleItems.build().isEmpty());
            if (!deleteIfExists(fileSystem, directory, false)) {
                return new RecursiveDeleteResult(false, ImmutableList.of(directory.toString() + "/"));
            }
            return new RecursiveDeleteResult(true, ImmutableList.of());
        }
        return new RecursiveDeleteResult(false, notDeletedEligibleItems.build());
    }

    /**
     * Attempts to remove the file or empty directory.
     *
     * @return true if the location no longer exists
     */
    private static boolean deleteIfExists(FileSystem fileSystem, Path path, boolean recursive)
    {
        try {
            // attempt to delete the path
            if (fileSystem.delete(path, recursive)) {
                return true;
            }

            // delete failed
            // check if path still exists
            return !fileSystem.exists(path);
        }
        catch (FileNotFoundException ignored) {
            // path was already removed or never existed
            return true;
        }
        catch (IOException ignored) {
        }
        return false;
    }

    /**
     * Attempts to remove the file or empty directory.
     *
     * @return true if the location no longer exists
     */
    private static boolean deleteRecursivelyIfExists(HdfsContext context, HdfsEnvironment hdfsEnvironment, Path path)
    {
        FileSystem fileSystem;
        try {
            fileSystem = hdfsEnvironment.getFileSystem(context, path);
        }
        catch (IOException ignored) {
            return false;
        }

        return deleteIfExists(fileSystem, path, true);
    }

    private static void renameDirectory(HdfsContext context, HdfsEnvironment hdfsEnvironment, Path source, Path target, Runnable runWhenPathDoesntExist)
    {
        if (pathExists(context, hdfsEnvironment, target)) {
            throw new PrestoException(HIVE_PATH_ALREADY_EXISTS,
                    format("Unable to rename from %s to %s: target directory already exists", source, target));
        }

        if (!pathExists(context, hdfsEnvironment, target.getParent())) {
            createDirectory(context, hdfsEnvironment, target.getParent());
        }

        // The runnable will assume that if rename fails, it will be okay to delete the directory (if the directory is empty).
        // This is not technically true because a race condition still exists.
        runWhenPathDoesntExist.run();

        try {
            if (!hdfsEnvironment.getFileSystem(context, source).rename(source, target)) {
                throw new PrestoException(HIVE_FILESYSTEM_ERROR, format("Failed to rename %s to %s: rename returned false", source, target));
            }
        }
        catch (IOException e) {
            throw new PrestoException(HIVE_FILESYSTEM_ERROR, format("Failed to rename %s to %s", source, target), e);
        }
    }

    private static Optional<String> getPrestoQueryId(Table table)
    {
        return Optional.ofNullable(table.getParameters().get(PRESTO_QUERY_ID_NAME));
    }

    private static Optional<String> getPrestoQueryId(Partition partition)
    {
        return Optional.ofNullable(partition.getParameters().get(PRESTO_QUERY_ID_NAME));
    }

    private void checkHoldsLock()
    {
        // This method serves a similar purpose at runtime as GuardedBy on method serves during static analysis.
        // This method should not have significant performance impact. If it does, it may be reasonably to remove this method.
        // This intentionally does not use checkState.
        if (!Thread.holdsLock(this)) {
            throw new IllegalStateException(format("Thread must hold a lock on the %s", getClass().getSimpleName()));
        }
    }

    private enum State
    {
        EMPTY,
        SHARED_OPERATION_BUFFERED,
        EXCLUSIVE_OPERATION_BUFFERED,
        FINISHED,
    }

    public enum WriteMode
    {
        STAGE_AND_MOVE_TO_TARGET_DIRECTORY, // common mode for new table or existing table (both new and existing partition)
        DIRECT_TO_TARGET_NEW_DIRECTORY, // for new table in S3
        DIRECT_TO_TARGET_EXISTING_DIRECTORY, // for existing table in S3 (both new and existing partition)

        // NOTE: Insert overwrite simulation (partition drops and partition additions in the same
        // transaction get merged and become one or more partition alterations, and get submitted to
        // metastore in close succession of each other) is not supported for S3. S3 uses the last
        // mode for insert into existing table. This is hard to support because the directory
        // containing the old data cannot be deleted until commit. Nor can the old data be moved
        // (assuming Hive HDFS directory naming convention shall not be violated). As a result,
        // subsequent insertion will have to write to directory belonging to existing partition.
        // This undermines the benefit of having insert overwrite simulation. This also makes
        // dropping of old partition at commit time hard because data added after the logical
        // "drop" time was added to the directories to be dropped.
    }

    private enum ActionType
    {
        DROP,
        ADD,
        ALTER,
        INSERT_EXISTING
    }

    private enum TableSource
    {
        CREATED_IN_THIS_TRANSACTION,
        PRE_EXISTING_TABLE,
        // RECREATED_IN_THIS_TRANSACTION is a possible case, but it is not supported with the current implementation
    }

    public static class Action<T>
    {
        private final ActionType type;
        private final T data;
        private final HdfsContext context;

        public Action(ActionType type, T data, HdfsContext context)
        {
            this.type = requireNonNull(type, "type is null");
            if (type == ActionType.DROP) {
                checkArgument(data == null, "data is not null");
            }
            else {
                requireNonNull(data, "data is null");
            }
            this.data = data;
            this.context = requireNonNull(context, "context is null");
        }

        public ActionType getType()
        {
            return type;
        }

        public T getData()
        {
            checkState(type != ActionType.DROP);
            return data;
        }

        public HdfsContext getContext()
        {
            return context;
        }

        @Override
        public String toString()
        {
            return toStringHelper(this)
                    .add("type", type)
                    .add("data", data)
                    .toString();
        }
    }

    private static class TableAndMore
    {
        private final Table table;
        private final Optional<PrincipalPrivileges> principalPrivileges;
        private final Optional<Path> currentLocation; // unpartitioned table only
        private final Optional<List<String>> fileNames;

        public TableAndMore(Table table, Optional<PrincipalPrivileges> principalPrivileges, Optional<Path> currentLocation, Optional<List<String>> fileNames)
        {
            this.table = requireNonNull(table, "table is null");
            this.principalPrivileges = requireNonNull(principalPrivileges, "principalPrivileges is null");
            this.currentLocation = requireNonNull(currentLocation, "currentLocation is null");
            this.fileNames = requireNonNull(fileNames, "fileNames is null");

            checkArgument(!table.getStorage().getLocation().isEmpty() || !currentLocation.isPresent(), "currentLocation can not be supplied for table without location");
            checkArgument(!fileNames.isPresent() || currentLocation.isPresent(), "fileNames can be supplied only when currentLocation is supplied");
        }

        public Table getTable()
        {
            return table;
        }

        public PrincipalPrivileges getPrincipalPrivileges()
        {
            checkState(principalPrivileges.isPresent());
            return principalPrivileges.get();
        }

        public Optional<Path> getCurrentLocation()
        {
            return currentLocation;
        }

        public Optional<List<String>> getFileNames()
        {
            return fileNames;
        }

        @Override
        public String toString()
        {
            return toStringHelper(this)
                    .add("table", table)
                    .add("principalPrivileges", principalPrivileges)
                    .add("currentLocation", currentLocation)
                    .toString();
        }
    }

    public static class PartitionAndMore
    {
        private final Partition partition;
        private final Path currentLocation;
        private final Optional<List<String>> fileNames;

        public PartitionAndMore(Partition partition, Path currentLocation, Optional<List<String>> fileNames)
        {
            this.partition = requireNonNull(partition, "partition is null");
            this.currentLocation = requireNonNull(currentLocation, "currentLocation is null");
            this.fileNames = requireNonNull(fileNames, "fileNames is null");
        }

        @JsonCreator
        public PartitionAndMore jsonCreator(@JsonProperty("partition") Partition partition, @JsonProperty("currentLocation") Path currentLocation)
        {
            return new PartitionAndMore(partition, currentLocation, Optional.empty());
        }

        @JsonProperty
        public Partition getPartition()
        {
            return partition;
        }

        Partition getAugmentedPartitionForInTransactionRead()
        {
            // This method augments the location field of the partition to the staging location.
            // This way, if the partition is accessed in an ongoing transaction, staged data
            // can be found and accessed.
            Partition partition = this.partition;
            String currentLocation = this.currentLocation.toString();
            if (!currentLocation.equals(partition.getStorage().getLocation())) {
                partition = Partition.builder(partition)
                        .withStorage(storage -> storage.setLocation(currentLocation))
                        .build();
            }
            return partition;
        }

        @JsonProperty
        public Path getCurrentLocation()
        {
            return currentLocation;
        }

        public List<String> getFileNames()
        {
            checkState(fileNames.isPresent());
            return fileNames.get();
        }
    }

    private static class DeclaredIntentionToWrite
    {
        private final WriteMode mode;
        private final HdfsContext context;
        private final String filePrefix;
        private final Path rootPath;
        private final SchemaTableName schemaTableName;

        public DeclaredIntentionToWrite(WriteMode mode, HdfsContext context, Path stagingPathRoot, String filePrefix, SchemaTableName schemaTableName)
        {
            this.mode = requireNonNull(mode, "mode is null");
            this.context = requireNonNull(context, "context is null");
            this.rootPath = requireNonNull(stagingPathRoot, "stagingPathRoot is null");
            this.filePrefix = requireNonNull(filePrefix, "filePrefix is null");
            this.schemaTableName = requireNonNull(schemaTableName, "schemaTableName is null");
        }

        public WriteMode getMode()
        {
            return mode;
        }

        public HdfsContext getContext()
        {
            return context;
        }

        public String getFilePrefix()
        {
            return filePrefix;
        }

        public Path getRootPath()
        {
            return rootPath;
        }

        public SchemaTableName getSchemaTableName()
        {
            return schemaTableName;
        }

        @Override
        public String toString()
        {
            return toStringHelper(this)
                    .add("mode", mode)
                    .add("context", context)
                    .add("filePrefix", filePrefix)
                    .add("rootPath", rootPath)
                    .add("schemaTableName", schemaTableName)
                    .toString();
        }
    }

    private static class DirectoryCleanUpTask
    {
        private final HdfsContext context;
        private final Path path;
        private final boolean deleteEmptyDirectory;

        public DirectoryCleanUpTask(HdfsContext context, Path path, boolean deleteEmptyDirectory)
        {
            this.context = context;
            this.path = path;
            this.deleteEmptyDirectory = deleteEmptyDirectory;
        }

        public HdfsContext getContext()
        {
            return context;
        }

        public Path getPath()
        {
            return path;
        }

        public boolean isDeleteEmptyDirectory()
        {
            return deleteEmptyDirectory;
        }

        @Override
        public String toString()
        {
            return toStringHelper(this)
                    .add("context", context)
                    .add("path", path)
                    .add("deleteEmptyDirectory", deleteEmptyDirectory)
                    .toString();
        }
    }

    private static class DirectoryDeletionTask
    {
        private final HdfsContext context;
        private final Path path;

        public DirectoryDeletionTask(HdfsContext context, Path path)
        {
            this.context = context;
            this.path = path;
        }

        public HdfsContext getContext()
        {
            return context;
        }

        public Path getPath()
        {
            return path;
        }

        @Override
        public String toString()
        {
            return toStringHelper(this)
                    .add("context", context)
                    .add("path", path)
                    .toString();
        }
    }

    private static class DirectoryRenameTask
    {
        private final HdfsContext context;
        private final Path renameFrom;
        private final Path renameTo;

        public DirectoryRenameTask(HdfsContext context, Path renameFrom, Path renameTo)
        {
            this.context = requireNonNull(context, "context is null");
            this.renameFrom = requireNonNull(renameFrom, "renameFrom is null");
            this.renameTo = requireNonNull(renameTo, "renameTo is null");
        }

        public HdfsContext getContext()
        {
            return context;
        }

        public Path getRenameFrom()
        {
            return renameFrom;
        }

        public Path getRenameTo()
        {
            return renameTo;
        }

        @Override
        public String toString()
        {
            return toStringHelper(this)
                    .add("context", context)
                    .add("renameFrom", renameFrom)
                    .add("renameTo", renameTo)
                    .toString();
        }
    }

    private static class IrreversibleMetastoreOperation
    {
        private final String description;
        private final Runnable action;

        public IrreversibleMetastoreOperation(String description, Runnable action)
        {
            this.description = requireNonNull(description, "description is null");
            this.action = requireNonNull(action, "action is null");
        }

        public String getDescription()
        {
            return description;
        }

        public void run()
        {
            action.run();
        }
    }

    private static class CreateTableOperation
    {
        private final Table table;
        private final PrincipalPrivileges privileges;
        private boolean done;

        public CreateTableOperation(Table table, PrincipalPrivileges privileges)
        {
            requireNonNull(table, "table is null");
            checkArgument(getPrestoQueryId(table).isPresent());
            this.table = table;
            this.privileges = requireNonNull(privileges, "privileges is null");
        }

        public String getDescription()
        {
            return format("add table %s.%s", table.getDatabaseName(), table.getTableName());
        }

        public void run(ExtendedHiveMetastore metastore)
        {
            try {
                metastore.createTable(table, privileges);
                done = true;
            }
            catch (RuntimeException e) {
                try {
                    Optional<Table> remoteTable = metastore.getTable(table.getDatabaseName(), table.getTableName());
                    // getPrestoQueryId(partition) is guaranteed to be non-empty. It is asserted in the constructor.
                    if (remoteTable.isPresent() && getPrestoQueryId(remoteTable.get()).equals(getPrestoQueryId(table))) {
                        done = true;
                    }
                }
                catch (RuntimeException ignored) {
                    // When table could not be fetched from metastore, it is not known whether the table was added.
                    // Deleting the table when aborting commit has the risk of deleting table not added in this transaction.
                    // Not deleting the table may leave garbage behind. The former is much more dangerous than the latter.
                    // Therefore, the table is not considered added.
                }
                if (!done) {
                    throw e;
                }
            }
        }

        public void undo(ExtendedHiveMetastore metastore)
        {
            if (!done) {
                return;
            }
            metastore.dropTable(table.getDatabaseName(), table.getTableName(), false);
        }
    }

    private static class AlterPartitionOperation
    {
        private final Partition newPartition;
        private final Partition oldPartition;
        private boolean done;

        public AlterPartitionOperation(Partition newPartition, Partition oldPartition)
        {
            this.newPartition = requireNonNull(newPartition, "newPartition is null");
            this.oldPartition = requireNonNull(oldPartition, "oldPartition is null");
            checkArgument(newPartition.getDatabaseName().equals(oldPartition.getDatabaseName()));
            checkArgument(newPartition.getTableName().equals(oldPartition.getTableName()));
            checkArgument(newPartition.getValues().equals(oldPartition.getValues()));
        }

        public String getDescription()
        {
            return format("alter partition %s.%s %s", newPartition.getDatabaseName(), newPartition.getTableName(), newPartition.getValues());
        }

        public void run(ExtendedHiveMetastore metastore)
        {
            metastore.alterPartition(newPartition.getDatabaseName(), newPartition.getTableName(), newPartition);
            done = true;
        }

        public void undo(ExtendedHiveMetastore metastore)
        {
            if (!done) {
                return;
            }
            metastore.alterPartition(oldPartition.getDatabaseName(), oldPartition.getTableName(), oldPartition);
        }
    }

    private static class PartitionAdder
    {
        private final String schemaName;
        private final String tableName;
        private final ExtendedHiveMetastore metastore;
        private final int batchSize;
        private final List<Partition> partitions;
        private List<List<String>> createdPartitionValues = new ArrayList<>();

        public PartitionAdder(String schemaName, String tableName, ExtendedHiveMetastore metastore, int batchSize)
        {
            this.schemaName = schemaName;
            this.tableName = tableName;
            this.metastore = metastore;
            this.batchSize = batchSize;
            this.partitions = new ArrayList<>(batchSize);
        }

        public String getSchemaName()
        {
            return schemaName;
        }

        public String getTableName()
        {
            return tableName;
        }

        public void addPartition(Partition partition)
        {
            checkArgument(getPrestoQueryId(partition).isPresent());
            partitions.add(partition);
        }

        public void execute()
        {
            List<List<Partition>> batchedPartitions = Lists.partition(partitions, batchSize);
            for (List<Partition> batch : batchedPartitions) {
                try {
                    metastore.addPartitions(schemaName, tableName, batch);
                    for (Partition partition : batch) {
                        createdPartitionValues.add(partition.getValues());
                    }
                }
                catch (Throwable t) {
                    // Add partition to the created list conservatively.
                    // Some metastore implementations are known to violate the "all or none" guarantee for add_partitions call.
                    boolean batchCompletelyAdded = true;
                    for (Partition partition : batch) {
                        try {
                            Optional<Partition> remotePartition = metastore.getPartition(schemaName, tableName, partition.getValues());
                            // getPrestoQueryId(partition) is guaranteed to be non-empty. It is asserted in PartitionAdder.addPartition.
                            if (remotePartition.isPresent() && getPrestoQueryId(remotePartition.get()).equals(getPrestoQueryId(partition))) {
                                createdPartitionValues.add(partition.getValues());
                            }
                            else {
                                batchCompletelyAdded = false;
                            }
                        }
                        catch (Throwable ignored) {
                            // When partition could not be fetched from metastore, it is not known whether the partition was added.
                            // Deleting the partition when aborting commit has the risk of deleting partition not added in this transaction.
                            // Not deleting the partition may leave garbage behind. The former is much more dangerous than the latter.
                            // Therefore, the partition is not added to the createdPartitionValues list here.
                            batchCompletelyAdded = false;
                        }
                    }
                    // If all the partitions were added successfully, the add_partition operation was actually successful.
                    // For some reason, it threw an exception (communication failure, retry failure after communication failure, etc).
                    // But we would consider it successful anyways.
                    if (!batchCompletelyAdded) {
                        throw t;
                    }
                }
            }
            partitions.clear();
        }

        public List<List<String>> rollback()
        {
            // drop created partitions
            List<List<String>> partitionsFailedToRollback = new ArrayList<>();
            for (List<String> createdPartitionValue : createdPartitionValues) {
                try {
                    metastore.dropPartition(schemaName, tableName, createdPartitionValue, false);
                }
                catch (PartitionNotFoundException e) {
                    // Maybe some one deleted the partition we added.
                    // Anyways, we are good because the partition is not there anymore.
                }
                catch (Throwable t) {
                    partitionsFailedToRollback.add(createdPartitionValue);
                }
            }
            createdPartitionValues = partitionsFailedToRollback;
            return partitionsFailedToRollback;
        }
    }

    private static class RecursiveDeleteResult
    {
        private final boolean directoryNoLongerExists;
        private final List<String> notDeletedEligibleItems;

        public RecursiveDeleteResult(boolean directoryNoLongerExists, List<String> notDeletedEligibleItems)
        {
            this.directoryNoLongerExists = directoryNoLongerExists;
            this.notDeletedEligibleItems = notDeletedEligibleItems;
        }

        public boolean isDirectoryNoLongerExists()
        {
            return directoryNoLongerExists;
        }

        public List<String> getNotDeletedEligibleItems()
        {
            return notDeletedEligibleItems;
        }
    }

    private interface ExclusiveOperation
    {
        void execute(ExtendedHiveMetastore delegate, HdfsEnvironment hdfsEnvironment);
    }
}
