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/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hive.ql.lockmgr;
import org.apache.hadoop.hive.common.ValidTxnList;
import org.apache.hadoop.hive.ql.Context;
import org.apache.hadoop.hive.ql.QueryPlan;
import org.apache.hadoop.hive.ql.metadata.Hive;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.ql.plan.LockDatabaseDesc;
import org.apache.hadoop.hive.ql.plan.LockTableDesc;
import org.apache.hadoop.hive.ql.plan.UnlockDatabaseDesc;
import org.apache.hadoop.hive.ql.plan.UnlockTableDesc;
import java.util.List;
/**
* An interface that allows Hive to manage transactions. All classes
* implementing this should extend {@link HiveTxnManagerImpl} rather than
* implementing this directly.
*/
public interface HiveTxnManager {
/**
* Open a new transaction.
* @param ctx Context for this query
* @param user Hive user who is opening this transaction.
* @return The new transaction id
* @throws LockException if a transaction is already open.
*/
long openTxn(Context ctx, String user) throws LockException;
/**
* Get the lock manager. This must be used rather than instantiating an
* instance of the lock manager directly as the transaction manager will
* choose which lock manager to instantiate.
* @return the instance of the lock manager
* @throws LockException if there is an issue obtaining the lock manager.
*/
HiveLockManager getLockManager() throws LockException;
/**
* Acquire all of the locks needed by a query. If used with a query that
* requires transactions, this should be called after {@link #openTxn(Context, String)}.
* A list of acquired locks will be stored in the
* {@link org.apache.hadoop.hive.ql.Context} object and can be retrieved
* via {@link org.apache.hadoop.hive.ql.Context#getHiveLocks}.
*
* @param plan query plan
* @param ctx Context for this query
* @param username name of the user for this query
* @throws LockException if there is an error getting the locks. Use {@link LockException#getCanonicalErrorMsg()}
* to get more info on how to handle the exception.
*/
void acquireLocks(QueryPlan plan, Context ctx, String username) throws LockException;
/**
* Release specified locks.
* Transaction aware TxnManagers, which has {@code supportsAcid() == true},
* will track locks internally and ignore this parameter
* @param hiveLocks The list of locks to be released.
*/
void releaseLocks(List hiveLocks) throws LockException;
/**
* Commit the current transaction. This will release all locks obtained in
* {@link #acquireLocks(org.apache.hadoop.hive.ql.QueryPlan,
* org.apache.hadoop.hive.ql.Context, java.lang.String)}.
* @throws LockException if there is no current transaction or the
* transaction has already been committed or aborted.
*/
void commitTxn() throws LockException;
/**
* Abort the current transaction. This will release all locks obtained in
* {@link #acquireLocks(org.apache.hadoop.hive.ql.QueryPlan,
* org.apache.hadoop.hive.ql.Context, java.lang.String)}.
* @throws LockException if there is no current transaction or the
* transaction has already been committed or aborted.
*/
void rollbackTxn() throws LockException;
/**
* Send a heartbeat to the transaction management storage so other Hive
* clients know that the transaction and locks held by this client are
* still valid. For implementations that do not require heartbeats this
* can be a no-op.
* @throws LockException If current transaction exists or the transaction
* has already been committed or aborted.
*/
void heartbeat() throws LockException;
/**
* Get the transactions that are currently valid. The resulting
* {@link ValidTxnList} object is a thrift object and can
* be passed to the processing
* tasks for use in the reading the data. This call should be made once up
* front by the planner and should never be called on the backend,
* as this will violate the isolation level semantics.
* @return list of valid transactions.
* @throws LockException
*/
ValidTxnList getValidTxns() throws LockException;
/**
* Get the name for currently installed transaction manager.
* @return transaction manager name
*/
String getTxnManagerName();
/**
* This call closes down the transaction manager. All open transactions
* are aborted. If no transactions are open but locks are held those locks
* are released. This method should be called if processing of a session
* is being halted in an abnormal way. It avoids locks and transactions
* timing out.
*/
void closeTxnManager();
/**
* Indicate whether this lock manager supports the use of lock
* database or lock table.
* @return
*/
boolean supportsExplicitLock();
/**
* This function is called to lock the table when explicit lock command is
* issued on a table.
* @param hiveDB an object to communicate with the metastore
* @param lockTbl table locking info, such as table name, locking mode
* @return 0 if the locking succeeds, 1 otherwise.
* @throws HiveException
*/
int lockTable(Hive hiveDB, LockTableDesc lockTbl) throws HiveException;
/**
* This function is called to unlock the table when explicit unlock command is
* issued on a table.
* @param hiveDB an object to communicate with the metastore
* @param unlockTbl table unlocking info, such as table name
* @return 0 if the locking succeeds, 1 otherwise.
* @throws HiveException
*/
int unlockTable(Hive hiveDB, UnlockTableDesc unlockTbl) throws HiveException;
/**
* This function is called to lock the database when explicit lock command is
* issued on a database.
* @param hiveDB an object to communicate with the metastore
* @param lockDb database locking info, such as database name, locking mode
* @return 0 if the locking succeeds, 1 otherwise.
* @throws HiveException
*/
int lockDatabase(Hive hiveDB, LockDatabaseDesc lockDb) throws HiveException;
/**
* This function is called to unlock the database when explicit unlock command
* is issued on a database.
* @param hiveDB an object to communicate with the metastore
* @param unlockDb database unlocking info, such as database name
* @return 0 if the locking succeeds, 1 otherwise.
* @throws HiveException
*/
int unlockDatabase(Hive hiveDB, UnlockDatabaseDesc unlockDb) throws HiveException;
/**
* Indicate whether this transaction manager returns information about locks in the new format
* for show locks or the old one.
* @return true if the new format should be used.
*/
boolean useNewShowLocksFormat();
/**
* Indicate whether this transaction manager supports ACID operations
* @return true if this transaction manager does ACID
*/
boolean supportsAcid();
/**
* This behaves exactly as
* https://docs.oracle.com/javase/6/docs/api/java/sql/Connection.html#setAutoCommit(boolean)
*/
void setAutoCommit(boolean autoCommit) throws LockException;
/**
* This behaves exactly as
* https://docs.oracle.com/javase/6/docs/api/java/sql/Connection.html#getAutoCommit()
*/
boolean getAutoCommit();
boolean isTxnOpen();
/**
* if {@code isTxnOpen()}, returns the currently active transaction ID
*/
long getCurrentTxnId();
/**
* Should be though of more as a unique write operation ID in a given txn (at QueryPlan level).
* Each statement writing data within a multi statement txn should have a unique WriteId.
* Even a single statement, (e.g. Merge, multi-insert may generates several writes).
*/
int getWriteIdAndIncrement();
}
