hive drop table without deleting data
03:37 PM. IMPALA; IMPALA-1044; Drop Table in Impala does not delete the data, while Hive does. Ex: UseCase 1: 1. Alter back the table as external=True. Specifies the type of the table. Second Way: If we want to drop the hive database without dropping the current database tables. If the table is dropped, then the table metadata and the data will be deleted. To find out if a table is managed or external, look for tableType in the output of DESCRIBE EXTENDED table_name. (NOT WORKING) Note : In all the above cases, skipTrash is set in hive library. External Tables : Hive does not move the data into its warehouse directory. You need to take additional steps. Drop the partitions -- when you drop the partitions, data pertained to the partitions will also be dropped as now this table is managed table . The location is user-configurable when Hive is installed. If PURGE is specified, then data is lost completely. We saw un-partitioned and partitioned tables. 06-28-2018 The DROP TABLE statement in Hive deletes the data for a particular table and remove all metadata associated with it from Hive metastore. student_id INT,
However, managed tables are less convenient for sharing with other tools. Select a database from the drop-down list or click New to create one. However, after longer use I've found that fetching the data from these tables became broken: i.e., count(*) from that table estimates 2k rows, while export using beeline to csv returns >100k rows, most of which are NULL's at the end of the file. 2. We cannot drop the exiting database with subject to the database is empty. Delta Lake managed tables in particular contain a lot of metadata in the form of transaction logs, and they can contain duplicate data files. By running ALTER TABLE ... DROP PARTITION ... you are only deleting the data and metadata for the matching partitions, not the partitioning of the table itself. For instance, if we create a table and realize that the schema is wrong, we can safely drop the table and recreate with the new schema without worrying about the data.Other advantage is that if we are using other tools like pig on same files, we can continue using them even after we delete the table. This is the behavior in Hive. Created Steps The content you requested has been removed. First of all, In order to understand the data type in sqoop and hive let's create following scenario. By running ALTER TABLE ... DROP PARTITION ... you are only deleting the data and metadata for the matching partitions, not the partitioning of the table itself. The following shows the syntax of the DROP DATABASE statement: If we will drop the internal or manage table then the table DDL, metadata information, and table data … While running the same data step again (after deletion), i,e. Open new terminal and fire up hive by just typing hive. 1 min read. When you drop a table from Hive Metastore, it removes the table/column data and their metadata. " Hive is just a part of the big puzzle called Big Data and Hadoop " What is Hive? You’ll be auto redirected in 1 second. Hive>LOAD DATA INPATH '/user/guru99hive/data.txt' INTO table guruhive_internaltable; 3. Internal table is called Manage table as well and for External tables Hive assumes that it does not manage the data. Partitioning is defined when the table is created. So I made a research here, and saw smtg interesting (not sure if this is your case, as you're using SQLContext). Just like deleting a file, the contents can sometimes be recovered using recovery or forensic tools, but when you delete a partition, you’ll delete everything inside it. hive> ALTER TABLE
SET TBLPROPERTIES('EXTERNAL'='False'); //changing the tbl properties to to make the table as internal hive> drop table ; //now the table is internal if you drop the table data will be dropped automatically. How can we be sure that dropping the old tables also drops the data? Any insight would be greatly appreciated. Summary : In Data step - both in case 1 and 2 - I am not able to delete the underlying HDFS file. The data is actually moved to the .Trash/Current directory if Trash is configured (and PURGE is not specified). DROP TABLE removes metadata and data for this table. Before becoming a open source project of Apache Hadoop, Hive … Through a
However, the latest version of Apache Hive supports ACID transaction, but using ACID transaction on table with huge amount of data may kill the performance of Hive server. Hive manages two different types of tables. Transactional Tables: Hive supports single-table transactions. Azure Blob storage is a robust, general-purpose storage solution that integrates seamlessly with HDInsight. Options. When we drop a managed table (see Dropping Tables), Hive deletes the data in the table. The merge statement streamlines updates, deletes, and changes data capture operations by drawing on co-existing tables. Hi,Here is the script: https://github.com/Naveen3Singh/drop_db-tableThanks for Watching!Bye Through a
@dthakkar @Vinicius Higa Murakami any ideas? 08:35 AM. Sometimes, we have a requirement to remove duplicate events from the hive table … Any insight would be greatly appreciated. If PURGE is not specified then the data is actually moved to the .Trash/current directory. In HIVE-9083/HIVE-9086, I extended this to work when partitions are dropped.. Someone has dropped a table from your database and you want to track who did it. One exception to this is the default database in Hive which does not have a directory. On dropping these tables the data stored in them also gets deleted and data is lost forever. https://spark.apache.org/docs/1.6.1/sql-programming-guide.html#saving-to-persistent-tablesAnyways, hope this helps you! Am I correct in assuming that dropping an internal table will not remove the contents of the container because HDInsight uses Azure Blob Storage as its storage and not HDFS? Regardless of how you drop a managed table, it can take a significant amount of time, depending on the data size. We’re sorry. From the following screenshot, we can observe the output In above code and from screen shot we do following things, However for an external table only the metadata of the table is cleared and the data still persists as it is in its place. insert_date STRING)
Write a script which can execute below statement for all the tables that are in warehouse directory. The container contains a bunch of text files. Follow below steps to remove columns from Hive table using intermediate or temporary tables. if we will delete/drop the external table. 3. Type ... Labels: None. If its Hive Managed table, hive will delete table structure as well as data associated with hive table. In HIVE-9083/HIVE-9086, I extended this to work when partitions are dropped.. creating the same table in the schema - the number of records ingested is incorrect. Internal table and External table. HDInsight uses Azure Blob storage instead for data storage. The data format in the files is assumed to be field-delimited by ctrl-A and row-delimited by newline. LOCAL – Use LOCAL if you have a file in the server where the beeline is running.. OVERWRITE – It deletes the existing contents of the table and replaces with the new content.. PARTITION – Loads data into specified partition.. INPUTFORMAT – Specify Hive input format to load a specific file format into table, it takes text, ORC, CSV etc.. SERDE – can be the associated Hive SERDE. "The original HDFS uses of many local disks on the cluster. For example, suppose we have data that is created and used primarily by Pig or other tools, but we want to run some queries against it, but not give Hive ownership of the data. When dropping an EXTERNAL table, data in the table will NOT be deleted from the file system. 06-29-2018 If a Delta table has been in use for a long time, it can accumulate a very large amount of data. Even when we replace columns in hive text table the data will not be changed i.e wikipedia_link data will be still presented in HDFS file.. Deleting the table should drop both metadata and deletes the hdfs data. One of the advantages of using an external table is that we can drop the table without deleting the data. We saw un-partitioned and partitioned tables. Then we can use the “CASCADE” keyword in the drop query. It means dropping respective tables before dropping the database. We do not need to create this database. These statements support auto-commit that treats each statement as a separate transaction and commits it after the SQL statement is executed. The DROP DATABASE statement drops all tables in the database and deletes the database permanently. By default the DBCREATE_TABLE_EXTERNAL is NO, which means SAS will create a managed table i.e. The JDBC program to drop a database is given below. But drop table from Impala deletes the table metadata without deleting the files. creating the same table in the schema - the number of records ingested is incorrect. Load data local inpath ‘aru.txt’ into table tablename and then we check employee1 table by using Select * from table name command Originally developed by Facebook to query their incoming ~20TB of data each day, currently, programmers use it for ad-hoc querying and analysis over large data sets stored in file systems like HDFS (Hadoop Distributed Framework System) without having to know specifics of map-reduce. 08:47 AM. hive> dfs -ls /user/hive/warehouse ; Found 2 items drwxr-xr-x - hduser supergroup 0 2017-03-31 18:37 /user/hive/warehouse/hive.db drwxr-xr-x - hduser supergroup 0 2017-03-29 18:44… Export. The metadata is completely lost. Note that a table cannot be dropped without removing the referencing constraint or the table first; Types of data to script – select Schema and data, if there is a need to recover the lost records, too: Once the script has been generated, it can be opened, reviewed and modified. This blog post was published on Hortonworks.com before the merger with Cloudera. One of the advantages of using an external table is that we can drop the table without deleting the data. In this tip, we will look at how you can use the transaction log to track down some of this info If an user created a table and loaded data into it and another user drop the table then only table will be droped but underlined data will exists . hive> DROP DATABASE IF EXISTS userdb CASCADE; The following query drops the database using SCHEMA. The below table is created in the location specified and it comes handy when we already have data. If the database is empty, then only we can drop the database. https://azure.microsoft.com/en-in/documentation/articles/hdinsight-provision-clusters/, Specifically the following extract:
We often drop and recreate Hive tables with new/recalculated data under same table names. Hi, When we drop a managed table , Hive deletes the data in the table is my understanding. https://azure.microsoft.com/en-in/documentation/articles/hdinsight-provision-clusters/. The default database in hive is default. "The original HDFS uses of many local disks on the cluster. We loaded data into it and realized that hive will create appropriate directory and copy files into those directories. If its external table, hive will drop table structure but not data as it is not managed by Hive but stored in specified location in HDFS. Hive Indexes - Learn Hive in simple and easy steps from basic to advanced concepts with clear examples including Introduction, Architecture, Installation, Data Types, Create Database, Use Database, Alter Database, Drop Database, Tables, Create Table, Alter Table, Load Data to Table, Insert Table, Drop Table, Views, Indexes, Partitioning, Show, Describe, Built-In Operators, Built-In Functions