hive unlock table partition

Bucketing works based on the value of hash function of some column of a table. Hadoop Troubleshooting Guide - Eric's Blog, HIVE-3509 – Exclusive locks are not acquired when using dynamic partitions, Query to Hive RCFile table with error “LazySimpleSerDe: expects either BytesWritable or Text object”, Dynamic Partitioning “INSERT OVERWRITE” Does Not Lock Table Exclusively, How to query a multiple delimited table in Hive, How to Find Out the Query That Locked Hive Table, Load Data From File Into Compressed Hive Table, How to create a Hive multi-character delimitered table. However, with the help of CLUSTERED BY clause and optional SORTED BY clause in CREATE TABLE statement we can create bucketed tables. Both internal/managed and external table supports column partition. Let us create a table to manage “Wallet expenses”, which any digital wallet channel may have to track customers’ spend behavior, having the following columns: In order to track monthly expenses, we want to create a partitioned table with columns month and spender. unlock schema.Table-name PARTITION(country_code='KR'); Error that happens is: Return code 1 from org.apache.hadoop.hive.q1.exec.DDLTask.partion spec {country_code=KR} doesnt contain all (5) partition columns Yes, you are correct that at ‘t’ + 10 minutes, the table has shared lock status and p1 partition has an exclusive lock. When Hive runs a query, it will create a znode in ZK under /hive_zookeeper_namespace_hive/, and if in the case of partitions, it will be under /hive_zookeeper_namespace_hive//=. If so, how can we handle read and write queries in parallel (you understand that a reading process cannot wait 20 long minutes in real life!)? This little nifty ruby snippet helps you get the unlock table statements that you can paste on your Hive CLI. You don’t really have a choice, and you should not anyway for consistent. Apache Hive is the data warehouse on the top of Hadoop, which enables ad-hoc analysis over structured and semi-structured data. This blog will help you to answer what is Hive partitioning, what is the need of partitioning, how it improves the performance? Can we have one partition at different locations? irb> s = Date.new ( 2014, 03, 01) # The start date of the partitions irb> e = Date.new ( 2014, 05, 01) # The end … The partitioning in Hive means dividing the table into some parts based on the values of a particular column like date, course, city or country. Partitioning is the way to dividing the table based on the key columns and organize the records in a partitioned manner. View my verified achievement from @SnowflakeDB. First we will create a temporary table, without partitions. [email protected]_del_req_status2 SHARED Suppose a table T has been partitioned statically. When you INSERT OVERWRITE into the same partition while reading it, the EXCLUSIVE lock will be placed on the partition for this query, and the query will still READ first and then WRITE, so there is no race conditions here, the query should still work. However, if user decides for whatever reason, he/she does not want others to view or update the table, then locking can be used. Here while loading the table, the partition will be created dynamically on all partition columns if hive.exec.dynamic.partition.mode= nonstrict is set. Hive takes partition values from … A big pain in the butt. insert overwrite table order_partition partition (year,month) select order_id, order_date, order_status, substr (order_date,1,4) ye, substr (order_date,5,2) mon from orders; This will insert data to year and month partitions for the order table. If you have the table partitioned, and READING and WRITING are operating on different partitions, then that will work, as they will not interfere with each other. In this case, because the GitHub data is stored in directories of the form 2017/01/01, the crawlers use default names like partition_0, partition_1, and so on. The Hive tutorial explains about the Hive partitions. ANTLR ANother Tool for Language Recognition can generate a grammar that can be built and walked. There is a upstream Hive JIRA issue,you can have a look at HIVE-3509 – Exclusive locks are not acquired when using dynamic partitions for more information. So you are right that it should be EXCLUSIVE in this case, but due to the bug, currently it is not. Save my name, email, and site URL in my browser for next time I post a comment. I tested this under CDH5.3 and CDH5.4 and both of them have the bug present. This little nifty ruby snippet helps you get the unlock table statements that you can paste on your Hive CLI. Hive currently has ACID Transactions feature available. bin/beeline -u jdbc:hive2://127.0.0.1:10000 scott tiger -e 'show partitions zipcodes;' > partitions.txt #Use below, If you are using HiverServer1 and using Hive CLI hive -e 'show partitions zipcodes;' > partitions.txt Is there a way to fix this? Looks like there is no good way to unlock all partitions on a hive table. It is funny how we have so much information available to us but nobody teaches us how to learn. There are about 9000 partition values, I am trying to unlock a table with the below command. IF NOT EXISTS. 2. you do not have ZooKeeper enabled, which is required for locking to work in Hive. set hive.exec.reducers.bytes.per.reducer= Other queries against this partition will have to wait, regardless of whether reading or writing. Time taken: 0.076 seconds A table can be partitioned … why it is so ?? https://t.co/9lmsA6lhRJ, Proud to see @SnowflakeDB on the #FCMostInnovative Companies list for 2021! The job did not succeed and I killed the workflow. The EXCLUSIVE lock will only apply to certain partitions that the query will run over. Dynamic partition is a single insert to the partition table. Required fields are marked *. CREATE TABLE expenses (Month String, Spender String, Merchant String, Mode String, Amount Float ) PARTITIONED BY (Month STRING, Spender STRING) Row format delimited fields terminated by ","; We get to know the partition keys using the belo… Hive organizes tables into partitions. That’s all I have to say about locks in Hive, if I missed anything, please let me know in the comments. OK Create a temporary table Partitioning allows Hive to run queries on a specific set of data in the table based on the value of partition column used in the query. In my case, we are still using CDH5.13 (and yes it does exist) with Hive1.1 (so no ACID). They can be run at the same time and whoever finishes the last will overwrite the results from the previous one. In order to limit the maximum number of reducers: The hive partition is similar to table partitioning available in SQL server or any other RDBMS database tables. Looks like there is no good way to unlock all partitions on a hive table. Query ID = idscah_20200602170505_c627bf20-52cf-439d-808c-6cdd3b289071 For instance, it is reasonable to partition the log data of a web site by dates. FAILED: Execution Error, return code 1 from org.apache.hadoop.hive.ql.exec.DDLTask. If the data is large, partitioning the table is beneficial for queries that only need to scan a few partitions of the table. In Hive, the table is stored as files in HDFS. thanks! This current session where I have done the EXCLUSIVE LOCK. hive> lock table gdpr_del_req_status2 shared; In order to set a constant number of reducers: It is nothing but a directory that contains the chunk of data. However, beginning with Spark 2.1, Alter Table Partitions is also supported for tables defined using the datasource API. Partition eliminates creating smaller physical tables, accessing, and … CREATE TABLE hive_partitioned_table (id BIGINT, name STRING) COMMENT 'Demo: Hive Partitioned Parquet Table and Partition Pruning' PARTITIONED BY (city STRING COMMENT 'City') STORED AS PARQUET; INSERT INTO hive_partitioned_table PARTITION (city="Warsaw") VALUES (0, 'Jacek'); INSERT INTO hive_partitioned_table PARTITION (city="Paris") VALUES (1, 'Agata'); Using partition, it is easy to query a portion of the data. now above query is stuck. In order to change the average load for a reducer (in bytes): In order to post comments, please make sure JavaScript and Cookies are enabled, and reload the page. 2)EXCLUSIVE LOCK Total jobs = 3 Number of reduce tasks determined at compile time: 1 In that case the READ operation really has to wait. Thank you for an explanation, so I was going through your blog to full fill my requirement, so let me summarize you about my use case, I have to read the data from x table while reading the table I want to make sure that other writers should until current read completes because I have to truncate the table after that read operation. If a table is EXCLUSIVELY locked, then no other queries will be able to proceed until the table is unlocked. Hive will wait for the lock to be released before dropping the table. What do you suggest in above scenario? To do this, I have created two simple tables in my small cluster called “test” and “test_partitioned”. We can make Hive to run query only on a specific partition by partitioning the table and running queries on specific partitions. The REFRESH statement is typically used with partitioned tables when new data files are loaded into a partition by some non-Impala mechanism, such as a Hive or Spark job. Hive uses the statistics such as number of rows in tables or table partition to generate an optimal query plan. OK (2) Q_r a query which will simply read the whole table T (Select * from T) and which is launched at ‘t’ + 10minutes (ie Q_r is launched 10 minutes after Q_w). Configuration properties for Hive locking are described in Locking. Hive Partitions is a way to organizes tables into partitions by dividing tables into different parts based on partition keys. create [external ]table tbl_nm (col1 datatyape , col2 datatype ..) Partitioned By (coln datatype); create partition on hive managed table hive> lock table gdpr_del_req_status2 EXCLUSIVE; show Locks LockManager not specified. In addition to partitioning Hive tables, it is also beneficial to store the Hive data in … If you force READING while WRITING, then the READ operation will return unexpected results. Your email address will not be published. I think this is a common scenario. Based on the error message “LockManager not specified”, I suspect that you are either missing one or both of below: 1. hive.support.concurrency is not set to “true” So for the same query I ran above, I am able to run the following same query twice in two different Hive sessions and they will race with each other: Of course, you will have to enable dynamic partitioning for the above query to run. I suggest you to perform a simple test to confirm, but I believe that it is the case. Hope above answers your question. Time taken: 0.043 seconds This is one of the easiest methods to insert into a Hive partitioned table. SHOW PARTITIONS table_name [PARTITION (partition_spec)] [WHERE where_condition] ; --check if country partition has USA Normally currently users do not use manual locking on Hive tables, because Hive queries themselves will take care of that automatically. The columns can be partitioned on an existing table or while creating a new Hive table. Adding Partition To Table. My new Snowflake Blog is now live. set hive.exec.reducers.max= Moreover, we can create a bucketed_user table with above-given requirement with the help of the below HiveQL.CREATE TABLE bucketed_user( firstname VARCHAR(64), lastname VARCHAR(64), address STRING, city VARCHAR(64),state VARCHAR(64), post STRING, p… Launching Job 1 out of 3 I will not be updating this blog anymore but will continue with new contents in the Snowflake world! This can vastly improve query times on the table because it collects the row count, file count, and file size (bytes) that make up the data in the table and gives that to the query planner before execution. Initially, when no query is running against the “test” table, the table should have no locks: you will see that the table will be “SHARED” locked: “SHARED” lock is also called a “READ” lock, meaning, other people can still read from the table, but any writes will have to wait for it to finish. Unless I am mistaken, at the moment ‘t’ + 10minute: CREATE DATABASE HIVE_PARTITION; USE HIVE_PARTITION; 2. hive> lock table gdpr_del_req_status2 EXCLUSIVE; And consider two queries: (1) Q_w a query which writes to a partition ‘p1’ of T at time ‘t’ and which will take 30 minutes to complete. In college, I struggled with processing vast amounts of information. Then load the data into this temporary non-partitioned table. We can make Hive to run query only on a specific partition by partitioning the table and running queries on specific partitions. Hi Eric, Will there be a race condition between read and write if in the same query, I am reading a partition modifying it and performing INSERT OVERWRITE on that partition. We can run below query to add partition to table. let me start the explaining use cases. 1) SHARED LOCK Thank Eric for useful info!!! Thanks for visiting my blog and posting questions. To list table partition location: select TBLS.TBL_NAME,PARTITIONS.PART_NAME,SDS.LOCATION from SDS,TBLS,PARTITIONS where PARTITIONS.SD_ID = SDS.SD_ID and TBLS.TBL_ID=PARTITIONS.TBL_ID order by 1,2; Sample output: When I check the lock available for the current table and now I see that only ‘SHARED LOCK ‘ has been acquired by the latest write operation why is it so, it should be ‘EXCLUSIVE LOCK ‘ because of write op. For example, below example demonstrates Insert into Hive partitioned Table using values clause. I have INSERT OVERWRITE queries in HQL file which sometimes do not get the required locks because an end user could be querying data in the same table. First we had to discover that Spark uses ANTLR to generate its SQL parser. The uses of SCHEMA and DATABASE are interchangeable – they mean the same thing. Without partitioning, any query on the table in Hive will read the entire data in the table. If not possible, what’s the use of manual lock here? – partition ‘p1’ of T has an “Exclusive” status (because Q_w has locked this partition). OK The advantage of partitioning is that since the data is stored in slices, the query response time becomes faster. Thanks for visiting my blog and post questions. If not, please let me know. I have a usecase where I want the whole table to be locked as I want to overwrite it but there are many read queries which are coming all this time. hive> show locks gdpr_del_req_status2; If we have a large table then queries may take long time to execute on the whole table. Configuration. When I tried using the following hive command it gives me error. Now, what if we want to drop some partition or add a new partition to the table? Currently you have JavaScript disabled. Now if you want to write data to the table using query: “EXCLUSIVE” lock is also called a “WRITE” lock, meaning no one else is able to read or write to the table while the lock is present, all other queries will have to wait for the current query to finish before they can start. insert into table gdpr.gdpr_del_req_status2 PARTITION(req_dts) select req_id,tbl_guid,req_status,update_user ,current_date() as req_dts from gdpr.gdpr_del_req_status1 limit 2; Thanks for visiting and your question on my blog. If we have a large table then queries may take long time to execute on the whole table. correct me if I am wrong One user is locking one table as he is running some operations, If other user runs unlock table command manually, then what will happens ? You need to specify the partition column with values and the remaining records in the VALUES clause. Other than optimizer, hive uses mentioned statistics in many other ways. hive> desc gdpr_del_req_status2; 2. Create a database for this exercise. I would read an article/paper/concept and comprehend only some part of... Continue →. hive> select * from gdpr.gdpr_del_req_status2; Is there a way to alter the table Let’s discuss Apache Hive partiti… Your email address will not be published. Partition is helpful when the table has one or more Partition keys. [email protected]_del_req_status2 SHARED Support setting the format for a partition in a Hive table with Spark. EXCLUSIVE lock will prevent both READ and WRITE, while SHARED lock will only prevent WRITE. The basic syntax to partition is as below . Using where clause you can fetch specific partition information from the Hive table. Next, we create the actual table with partitions and load data from temporary table into partitioned table. Thanks for visiting my blog. do you know what happens if I try to obtain an exclusive lock on a table and someone is reading from it at that very moment (so shared lock is present)? I actually checked it myself after I posted a question it and you are absolotely right, i am getting the below error while executing “show locks tablename” If the lock is there for a long time, then the drop query might eventually fail. OK To be absolutely safe, Hive should have applied an EXCLUSIVE lock to the table to prevent any further update to the table and all partitions, but it does not. This is by design, otherwise why would we need the lock? Currently Hive has a bug that does not acquire EXCLUSIVE lock when dynamic partition is used, please refer to below JIRA in the upstream: https://issues.apache.org/jira/browse/HIVE-3509. Solved: I am using hdp 2.4.2 (hive - 1.2.1.2.4). I believe in that case the attempt to obtain the exclusive lock will have to wait until the shared lock is released (that’s the purpose of shared lock to prevent others from writing it). Hi Eric, Partition keys are basic elements for determining how the data is stored in the table. This article explains how table locking works in Hive by running a series hive commands and their outputs. It is a way of dividing a table into related parts based on the values of partitioned columns such as date, city, and department. If we consider that we are at ‘t’ + 10 minutes, there are 20 minutes left before Q_w finishes writing in ‘p1’, do I understand that ‘Q_r’ cannot return the result before writing in ‘ P1 ‘? let me explain my problem to you and try to simplify it. We have created partitioned tables, inserted data into them. now in another session, I am trying to write. Any command you run on Beeline or Hive CLI, it returns limited results, If you have more partitions and if you wanted to get all partitions of the table, use the below commands. The REFRESH statement makes Impala aware of the new data files so that they can be used in Impala queries. – table T has a “Shared” status and Partitioning is the optimization technique in Hive which improves the performance significantly. Currently Hive will enforce EXCLUSIVE lock while writing, which will cause any subsequent read on the same table will have to wait. set mapreduce.job.reduces=. Without partitioning, any query on the table in Hive will read the entire data in the table. Add partitions to the table, optionally with a custom location for each partition added. You can also manually lock tables whenever you want: The locking can also be applied to table partitions: When you write to a partition of a table using static partitioning, an EXCLUSIVE lock will be applied to the partition that will be written to, and SHARED lock will be applied to the table itself: However, there is a bug in Hive that when you try to run an “INSERT OVERWRITE” using dynamic partitioning, because Hive is unable to figure out which partitions need to be locked, it currently only applies “SHARED” lock to the table being updated. I have hive tables which are queried through queries in a file. However, since the table only has SHARED lock while Q_w is running against P1, Q_r should be permitted to start without waiting for Q_w to finish first, so you should not face any delay. Hortonworks supports it, however, Cloudera still considers this feature is experimental and currently does not support ACID in CDH. very helpful post, Eric! My question is the following : Time taken: 0.043 seconds 1. Let us try to answer these questions in this blog post. Click here for instructions on how to enable JavaScript in your browser. Thank you very much for your analysis and your sharing. To answer your question, no, you can’t drop a table if there is a shared lock. @FastCompany recognizes how… https://t.co/KFiE79SGBT, Snowflake Guide New Post: TIMESTAMP Function Returns Different Results When Sorted By Different Direction https://t.co/c37Jq0qESo. But the tables are still shown as locked on Hive CLI. I want to know how I can do a transaction after locking the table manually in terminal line. hive> now on another session i am not able to read/write How to manually lock and unlock table or partitions in hive session. Analyzing a table (also known as computing statistics) is a built-in Hive operation that you can execute to collect metadata on your table. Insert into Hive partitioned Table using Values Clause. Please correct my understanding if I am doing anything wrong. The scheduled query just fails in such cases breaking the workflow. The grammar for … hive> Again like limit this is applicable on entire table or on specific partitions. CREATE DATABASE was added in Hive 0.6 ().. Partitioning in Hive. which I already mentioned in my post. Let me answer them below: 1. I had invoked an oozie workflow which invoked a hive action for mentioned file. That means you have to manually unlock each partition. The query stuck good works, wait for another surprise on the current session I am not able to read/write ?? Can I drop table if shared lock is applied on the table. The locking can also be applied to table partitions: 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 … The WITH DBPROPERTIES clause was added in Hive 0.7 ().MANAGEDLOCATION was added to database in Hive 4.0.0 ().LOCATION now refers to the default directory for external tables and MANAGEDLOCATION refers to the default directory for managed tables. That means you have to manually unlock each partition. Click here for instructions on how to enable JavaScript in your browser. ©2021 Hadoop Troubleshooting Guide - Eric's Blog, How to Use JsonSerDe to Read JSON data in Hive, Hive Shows NULL Value to New Column Added to a Partitioned Table With Existing Data. You can see the locks on a table by issuing the following command: SHOW LOCKS ; SHOW LOCKS EXTENDED; SHOW LOCKS PARTITION (); SHOW LOCKS PARTITION () EXTENDED; See also EXPLAIN LOCKS. If the specified partitions already exist, nothing happens. A big pain in the butt. This is supported only for tables created using the Hive format. Partitioning is an important concept in Hive that partitions the table based on data by rules and patterns. We don’t need explicitly to create the partition over the table for which we need to do the dynamic partition. Tables or partitions are sub-divided into buckets, to provide extra structure to the data that may be used for more efficient querying. In this post, we will check Apache Hive table statistics – Hive ANALYZE TABLE command and some examples. For partitioned paths in Hive-style of the form key=val, crawlers automatically populate the column name. Hive Unlock All Partitions. so the fresh entries should be present. I am looking for a command/process that will release locks from Hive tables.