It is empty #292 Enabled with following properties in place. Hive has supported concurrency access and locking mechanisms since v0.7.0 and updated to a new lock manager in v0.13.0. There are about 9000 partition values, I am trying to unlock a table with the below command. Call getChildren( ) on the lock node without setting the watch flag. For all other operations, an 'X' lock is taken on the partition. Hive Version: Hive 1.2.1000. The following types can be detected: STRING, INTEGER, DATE, and TIMESTAMP. Concurrency support (http://issues.apache.org/jira/browse/HIVE-1293) is a must in databases and their use cases are well understood. Two new configurable parameters will be added to decide the number of retries for the lock and the wait time between each retry. To confirm the problem, I created a simple table: If it is WAITING the user should wait and call this method again before proceeding. As we can see from above, the SELECT on another partition(one=c/two=d) will wait for SHARED lock on the parent table which is blocked by the EXCLUSIVE lock on partition(one=a/two=b). This is acquired when a table/partition is read. Hive across Multiple Data Centers (Physical Clusters), {"serverDuration": 93, "requestCorrelationId": "e6827123bb2aa8eb"}, http://issues.apache.org/jira/browse/HIVE-1293, http://hadoop.apache.org/zookeeper/docs/r3.1.2/recipes.html#sc_recipes_Locks. If there is a child with a pathname starting with "write-" and a lower sequence number than the one obtained, the lock cannot be acquired. hive> LOCK TABLE test_partitioned PARTITION (p='p1') EXCLUSIVE; OK Time taken: 0.31 seconds hive> SHOW LOCKS test_partitioned PARTITION (p='p1'); OK [email protected] [email protected]=p1 EXCLUSIVE Time taken: 0.189 seconds, Fetched: 1 row(s) hive> SHOW LOCKS test_partitioned; OK Time taken: 0.105 seconds hive> UNLOCK TABLE test_partitioned PARTITION (p='p1'); OK Time taken: 0.136 seconds hive> SHOW LOCKS test_partitioned PARTITION (p='p1'); OK Time taken: 0.123 seconds hive… Based on this, the lock acquired for an operation is as follows: insert into T2(partition P2) select .. T1 partition P1, insert into T2(partition P.Q) select .. T1 partition P1. Note that in some cases, the list of objects may not be known -- for example in case of dynamic partitions, the list of partitions being modified is not known at compile time -- so, the list is generated conservatively. The recipe listed above will not work as specified, because of the hierarchical nature of locks. Note that instead of waiting, the lock request will be denied. Table create statement. These will be cleaned up by a background process running from a standalone Hive metastore process. Data in each partition may be furthermore divided into Buckets. Goal: This article explains what is the difference between Spark HiveContext and SQLContext. Simple illustration of locking in Hive when ACID is enabled. Exclusive lock: Also called X lock. Define a object with main function -- Helloworld. View transaction locks. Specifically, when MSSQL server is used as metastore, since it only allows 2100 parameters in a request, it causes failure in enqueueLockWithRetry. hive.support.concurrency=true. There is no immediate requirement to add an API to explicitly acquire any locks, so all locks would be acquired implicitly. Moreover, to identify a particular partition each table can have one or more partition keys. Using the default metastore, which is embedded in the HiveServer process and installed by Ambari, you cannot manage a partition automatically. " hive.metastore.limit.partition.request ", -1, " This limits the number of partitions (whole partition objects) that can be requested " + " from the metastore for a give table. DbLockManager stores and manages all transaction lock information in the Hive Metastore. Env: Hive metastore 0.13 on MySQL Root ... Goal: How to control the number of Mappers and Reducers in Hive on Tez. The existing locks will be released, and all of them will be retried after the retry interval. Goal: This article provides the SQL to list table or partition locations from Hive Metastore. For more information, see: Powered by a free Atlassian Confluence Open Source Project License granted to Apache Software Foundation. hive.compactor.worker.threads=1. For example, DML queries take a write-lock on partitions they are modifying while read queries take a read-lock on partitions they are reading. Key Takeaways 1. If the state is ACQUIRED then the user can proceed. Throws: We got a lot of exception as below when doing a drop table partition, which made hive query every every slow. SHOW LOCKS displays the locks on a table or partition. This article shows a sample code to load data into Hbase or MapRDB(M7) using Scala on Spark. Below tips can help you hands on this feature. Hive ACID tables manage data in base and delta files which increase the performance of the… The main goal of creating INDEX on Hive table is to improve the data retrieval speed and optimize query performance. For a partitioned table, the idea is as follows: A 'S' lock on table and relevant partition is acquired when a read is being performed. Component/s:Metastore. The query will scan through about 20,000 partition 4. Look at ZooKeeper recipes (http://hadoop.apache.org/zookeeper/docs/r3.1.2/recipes.html#sc_recipes_Locks) to see how read/write locks can be implemented using the zookeeper apis. hive.support.concurrency property enables locking. At a minimum, we want to support concurrent readers and writers whenever possible. A separate data directory is created for each distinct value combination in the partition columns. Since hive.support.concurrency=true, when the query is running, Hive will try to create one ZNode per partition in ZooKeeper to indicate that those partitions are locked 5. How to control the file numbers of hive table after inserting data on MapR-FS. Evaluate Confluence today. When dies abruptly it may leave locks behind. Since the number of partitions may not be known, an exclusive lock is supposed to be taken (but currently not due to HIVE-3509 bug) on the table, or the prefix that is known. What are the differences? hive.support.concurrency = true hive.enforce.bucketing = true hive.exec.dynamic.partition.mode = nonstrict hive.txn.manager =org.apache.hadoop.hive.ql.lockmgr.DbTxnManager hive.compactor.initiator.on = true hive.compactor.worker.threads = 1 Currently only orc file is format supported. Download and Install maven. Ans. Hive transactions, enabled by default, disables Zookeeper locking. The rational behind the lock mode to acquire is as follows: For a non-partitioned table, the lock modes are pretty intuitive. Understanding Hive joins in explain plan output. However, if the change is only applicable to the newer partitions, a 'S' lock is acquired on the table, whereas if the change is applicable to all partitions, a 'X' lock is acquired on the table. 1. a lock response, which will provide two things, the id of the lock (to be used in all further calls regarding this lock) as well as a state of the lock. Each partition has its own file directory. When querying a large partitioned table, acquiring lock on partitions fails due to limitation of the RDBMS used as metastore in total number of parameters it can accept. Call create( ) to create a node with pathname "/warehouse/T/read-". Hive partitioning is implemented by reorganizing the raw data into new directories. This Hive query runs against a table with millions of partitions 3. Thus, older partitions can be read and written into, while the newer partitions are being converted to RCFile. As a Hive administrator, you can get troubleshooting information about locks on a table, partition, or schema. e.g. Since the number of partitions may not be known, an exclusive lock is supposed to be taken (but currently not due to HIVE-3509 bug) on the table, or the prefix that is known. The 'S' lock for table T is specified as follows: The 'X' lock for table T is specified as follows: The proposed scheme starves the writers for readers. Dropping data files in respective table/partition folders from external tools for ex: spark. This is the lock node used later in the protocol. SHOW LOCKS PARTITION (); SHOW LOCKS PARTITION () EXTENDED. As the name suggests, multiple shared locks can be acquired at the same time, whereas X lock blocks all other locks. Hive uses shared locks to control what operations can run in parallel on partition/table. Hive 0.13.0 adds transactions with row-level ACID semantics, using a new lock manager. There are two types of lock provided as follows: Shared lock: Also called S lock, it allows being shared concurrently. Delete the node created in the first step and return. To enable the locking feature, hive.zookeeper.quorum and hive.support.concurrency need to be set. If the number of retries are really high, it can lead to a live lock. I will introduce 2 ways, one is normal load us... Goal: How to build and use parquet-tools to read parquet files. Fix Version/s:None. – Supports partitioned and non-partitioned tables, WHERE clause can specify partition but not required Restrictions – Table must have format that extends AcidInputFormat • currently ORC • work started on Parquet (HIVE-8123) – Table must be bucketed and not sorted • can use 1 bucket but this will restrict write parallelism – Table must be marked transactional • create table T(...) clustered by (a) into … Dynamic Partitioning “INSERT OVERWRITE” Does Not Lock Table Exclusively Today I have discovered a bug in Hive, that when user submits an “INSERT OVERWRITE” query with dynamic partitioning, Hive does not lock the underlining table “exclusively”, rather it only applies “shared” lock. It would be useful to add a mechanism to discover the current locks which have been acquired. You can turn off concurrency by setting the following variable to false: hive.support.concurrency. This is the lock node used later in the protocol. Two new configurable parameters will be added to decide the number of retries for … Labels: None. Solution: 1. Articles Related Column Directory Hierarchy The partition columns determine how the data is stored. The partitioning is defined by the user. Currently only "Share" and "Exclusive" locks are introduced. The following lock modes will be defined in hive (Note that Intent lock is not needed). Updates can only be performed at the level of a partition. hive.exec.dynamic.partition.mode=nonstrict. Remove Hive partition Locks. When a queries is shutdown its locks should be released immediately. INSERT OVERWRITE rewrites an entire partition, which forces more frequent partition creation and therefore increases load on the NameNode. Cluster Version: HDP -2.5.6.0. hive.compactor.initiator.on=true. The default Hive behavior will not be changed, and concurrency will not be supported. All the objects to be locked are sorted lexicographically, and the required mode lock is acquired. OpenKB is just my personal technical memo to record and share knowledge. Call create( ) to create a node with pathname "/warehouse/T/write-". Make sure to set the sequence and ephemeral flag. SHARED lock on parent table -- … Share lock is for read , and anything else requires Exclusive lock. Basically, for the purpose of grouping similar type of data together on the basis of column or partition key, Hive organizes tables into partitions. If there is a child with a pathname starting with "read-" or "write-" and a lower sequence number than the one obtained, the lock cannot be acquired. Que 13. SCHEMA and DATABASE are interchangeable – they mean the same thing. You can see the locks on a table by issuing the following command: Configuration properties for Hive locking are described in Locking. In case of long readers, it may lead to starvation for writers. When the table is being read, a S lock is acquired, whereas an X lock is acquired for all other operations (insert into the table, alter table of any kind etc.). Hive partitioning allows Hive queries to access only the necessary amount of data in Hive tables. Make sure to set the sequence and ephemeral flag. For example, it will cost 250s while executing use db_test; Log:2014-10-17 04:04:46,873 ERROR Datastore.Persist (Log4JLogger.java:error(115)) - Update of object "org. Clairvoyant utilizes the Hive ACID transaction property to manage transactional data (Insert/Update/Delete). Functions: … Hive supports concurrency and table/partition level locks. Sometime... Hive is trying to embrace CBO(cost based optimizer) in latest versions, and Join is one major part of it. Hive partition keys appear as normal columns when querying data from Cloud Storage. lock in hive Management Show SHOW LOCKS ; SHOW LOCKS EXTENDED; SHOW LOCKS PARTITION (); SHOW LOCKS PARTITION () EXTENDED; Conf Hive - Configuration (Variable) turn off the hive.support.concurrency conf parameters. In order to avoid deadlocks, a very simple scheme is proposed here. Description. SHOW LOCKS (DATABASE|SCHEMA) is supported from Hive 0.13 for DATABASE (see HIVE-2093) and Hive 0.14 for SCHEMA (see HIVE-6601). /opt/mapr/zookeeper/zookeeper-3.4.5/bin/zkCli.sh -server :, ls /hive_zookeeper_namespace/default/passwords, get /hive_zookeeper_namespace/default/passwords. For example, let us say you are executing Hive query with filter condition WHERE col1 = 100, without index hive will load entire table or partition to process records and with index on col1 would load part of HDFS file to process records. How to use Scala on Spark to load data into Hbase/MapRDB -- normal load or bulk load. Follow below link: http://... Goal: This article explains the configuration parameters for Oozie Launcher job. Delete the node created in the first step and return. Data Partitions (Clustering of data) in Hive Each Table can have one or more partition. On defining Hive Partition, in other words, it is a sub-directory in the table directory. Return code 1 from org.apache.hadoop.hive.q1.exec.DDLTask.partion spec {country_code=KR} doesnt contain all (5) partition columns. BigQuery supports three modes of hive partition schema detection: AUTO: Key names and types are automatically detected. Whenever a partition is being locked in any mode, all its parents are locked in 'S' mode. The Hive metastore acquires an exclusive lock on a table that enables partition discovery that can slow down other queries. Many commands can check the memory utilization of JAVA processes, for example, pmap, ps, jmap, jstat. When the table is partitioned, acquiring an exclusive lock on a partition causes shared lock to be acquired on the table itself to prevent incompatible concurrent changes from occurring, such as attempting to drop the table while a partition is being modified. There is no isolation of readers from changes made to Hive tables through insert overwrite, so readers may see partial files. All components of the lock will have the same state. See Hive Concurrency Model for information about locks. This is a cookbook for scala programming. For some operations, locks are hierarchical in nature -- for example for some partition operations, the table is also locked (to make sure that the table cannot be dropped while a new partition is being created). The delta table of the partition, mapped to hive, cannot be retrieved by presto. Before we ... Hive table contains files in HDFS, if one table or one partition has too many small files, the HiveQL performance may be impacted. 1. How to build and use parquet-tools to read parquet files, Difference between Spark HiveContext and SQLContext, How to list table or partition location from Hive Metastore, Hive on Tez : How to control the number of Mappers and Reducers. Considerations for illustration. Partition schema detection modes. DummyTxnManager + Dynamic Partition Insert.
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