hive drop table without deleting data
In the case of external tables, only the metadata is deleted. hive> DROP SCHEMA userdb; This clause was added in Hive 0.6. So, whenever you change an entity (e.g. Apache Hive is often referred to as a data warehouse infrastr u cture built on top of Apache Hadoop. Created Then we can use the “CASCADE” keyword in the drop query. Related Readings: Hive Temporary Tables and Examples; Here is the original Table form which we are going to drop first column. subject_id INT,
06-29-2018 Back up and restore Therefore, you should be very careful when using this statement. Storing data in Blob storage enables you to safely delete the HDInsight clusters that are used for computation without losing user data.". When using proc sql - drop table / proc delete / proc dataset - delete, the hive metadata is deleted i.e. If its Hive Managed table, hive will delete table structure as well as data associated with hive table. Regardless of how you drop a managed table, it can take a significant amount of time, depending on the data size. 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. Summary: in this tutorial, you will learn how to use the MySQL DROP DATABASE statement to delete an existing database in the server.. If the external table is dropped, then the table metadata is deleted but not the data. Display the content of the table Hive>select * from guruhive_internaltable; 4. IMPALA; IMPALA-1044; Drop Table in Impala does not delete the data, while Hive does. Create table on weather data. 04:14 PM. Created Related Readings: Hive Temporary Tables and Examples; Here is the original Table form which we are going to drop first column. It means dropping respective tables before dropping the database. Any insight would be greatly appreciated. Table Type. if we will delete/drop the external table. Hadoop distributed file system (HDFS) interface, the full set of components in HDInsight can operate directly on structured or unstructured data in Blob storage. 06-28-2018 I am writing this blog for, "How to Insert, Update and Delete records into a Hive table?" Further, there were cases when repeating the same select * .. > output.csv (from beeline) returned different number rows! [quickstart.cloudera:21000] > DROP database sample cascade; Query: drop database sample cascade Note − You cannot delete the “current database” in … LOCATION 'wasb://logs@myaccount.blob.core.windows.net/'; Yes, that would be correct. This blog post was published on Hortonworks.com before the merger with Cloudera. 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? By doing this, there more controlled on what we are deleting and drop the partitions rather than using hadoop rm command 08:23 AM. Select a database from the drop-down list or click New to create one. Till so far we have learned how to insert data into a table using INSERT statement, SQL Developer and from some other table so the only thing which is left now is how to delete data from a table. marks INT,
Open new terminal and fire up hive by just typing hive. Select whether the table is a managed or external table. Transactional Tables: Hive supports single-table transactions. The new table contains no rows. But drop table from Impala deletes the table metadata without deleting the files. Among several different ways of deleting data from a table the two most used ways are SQL Delete and Truncate command. HIVE: dropping the table does not remove data, Re: HIVE: dropping the table does not remove data, https://spark.apache.org/docs/1.6.1/sql-programming-guide.html#saving-to-persistent-tables, [ANNOUNCE] New Cloudera ODBC 2.6.12 Driver for Apache Impala Released, [ANNOUNCE] New Cloudera JDBC 2.6.20 Driver for Apache Impala Released, Transition to private repositories for CDH, HDP and HDF, [ANNOUNCE] New Applied ML Research from Cloudera Fast Forward: Few-Shot Text Classification, [ANNOUNCE] New JDBC 2.6.13 Driver for Apache Hive Released. Hadoop distributed file system (HDFS) interface, the full set of components in HDInsight can operate directly on structured or unstructured data in Blob storage. 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 The following shows the syntax of the DROP DATABASE statement: When a table is dropped, the data in case of managed tables gets cleaned up. 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. By default the DBCREATE_TABLE_EXTERNAL is NO, which means SAS will create a managed table i.e. Lastly, some of the tables, used in constructing the join, are made in pySpark with the following manner: I'm wondering, whether the file structure imposed by python (or something like that) may be incompatible with hive tables? "drop table mytable" to delete both the table metadata and its contents. creating the same table in the schema - the number of records ingested is incorrect. If the data is directly deleted without moving to HDFS Trash, there is no way to recover those files. Drop employee) to drop hive table data. But I think this is not the case (at least in my case), the default option is dropping the hive table … This option is feasible when you have data in the table. A managed table means the table data is managed by hive. The metadata is completely lost. First of all, In order to understand the data type in sqoop and hive let's create following scenario. While running the same data step again (after deletion), i,e. Log In. Delta Lake managed tables in particular contain a lot of metadata in the form of transaction logs, and they can contain duplicate data files. Deleting the table should drop both metadata and deletes the hdfs data. If we will drop the internal or manage table then the table DDL, metadata information, and table data … However for an external table only the metadata of the table is cleared and the data still persists as it is in its place. You mentioned that you're using pyspark right? Description. UseCase 2: 1. If PURGE is not specified then the data is actually moved to the .Trash/current directory. When we drop those tables, hive removes directory and data files both. You’ll be auto redirected in 1 second. So my question: is there a fix for this? Managed and External tables can be identified using the DESCRIBE FORMATTED table_name command, which will display either Manage table or External table depending on table type. 07-04-2018 If the database is empty, then only we can drop the database. When you drop a table from Hive Metastore, it removes the table/column data and their metadata. On dropping these tables the data stored in them also gets deleted and data is lost forever. Attachments. The merge statement streamlines updates, deletes, and changes data capture operations by drawing on co-existing tables. Follow below steps to remove columns from Hive table using intermediate or temporary tables. 07-04-2018 However, dropping the Hive table doesn't appear to delete the contents of the container. 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> 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… If you do though it violates invariants and expectations of Hive and you might see undefined behavior. How can we be sure that dropping the old tables also drops the data? If you want the DROP TABLE command to also remove the actual data in the external table, as DROP TABLE does on a managed table, you need to configure the table properties accordingly. The below table is created in the location specified and it comes handy when we already have data. One of the advantages of using an external table is that we can drop the table without deleting the data. We cannot drop the exiting database with subject to the database is empty. Someone has dropped a table from your database and you want to track who did it. Write a script which can execute below statement for all the tables that are in warehouse directory. Load data local inpath ‘aru.txt’ into table tablename and then we check employee1 table by using Select * from table name command In this blog I will explain how to configure the hive to perform the ACID operation. However, dropping the Hive table doesn't
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. For External Tables - Created When we drop those tables, hive removes directory and data files both. Find answers, ask questions, and share your expertise. 06-29-2018 We loaded data into it and realized that hive will create appropriate directory and copy files into those directories. Sorry for the long delay, so regarding your issue. Or external? By default, Hive creates an Internal table also known as the Managed table, In the managed table, Hive owns the data/files on the table meaning any data you insert or load files to the table are managed by the Hive process when you drop the table the underlying data or files are also get deleted. Lets delete all the table from hive database. Because that's what a managed table is, as compared to an external one. Hadoop Flags: Reviewed. When dropping an EXTERNAL table, data in the table will NOT be deleted from the file system. Second Way: If we want to drop the hive database without dropping the current database tables. 4. It can be a normal table (stored in Metastore) or an external table (stored in local file system); Hive treats both in the same manner, irrespective of their types. The JDBC program to drop a database is given below. You can easily remove the metadata and convert it back into a Hive table, so there is minimal risk. The TBLPROPERTIES clause allows you to tag the table definition with your own metadata key/value pairs. So I made a research here, and saw smtg interesting (not sure if this is your case, as you're using SQLContext). However, managed tables are less convenient for sharing with other tools. 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. External ... An external table describes the metadata / schema on external files. The ‘Drop Table’ statement deletes the data and metadata for a table. Afterward, you must rebuild any global indexes (whether partitioned or not) because the index (or index partitions) has been marked UNUSABLE.The following statements provide an example of dropping partition dec98 from the sales table, then rebuilding its global nonpartitioned index. 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. Hive>DROP TABLE guruhive_internaltable; If you dropped the guruhive_internaltable, including its metadata and its data will be deleted from Hive. A table created without the EXTERNAL clause is called a managed table because Hive manages its data. ROW FORMAT DELIMITED FIELDS TERMINATED BY ','
Hi, When we drop a managed table , Hive deletes the data in the table is my understanding. Those extra rows were made of NULL's, that's why I'm guessing that it doesn't manage leftover files well. XML Word Printable JSON. Azure Blob storage is a robust, general-purpose storage solution that integrates seamlessly with HDInsight. how to drop partition metadata from hive, when partition is drop by using alter drop command. Specifies the type of the table. Partitioning is defined when the table is created. Now about the issue, it's kinda strange to me. To drop the internal table Hive>DROP TABLE guruhive_internaltable; If you dropped the guruhive_internaltable, including its metadata and its data will be deleted from Hive. You need to take additional steps. hive> DROP DATABASE IF EXISTS userdb CASCADE; The following query drops the database using SCHEMA. Options. table structure is dropped from the schema but the underlying HDFS file is not. In the hive, we can drop or delete the database form from the hive system. That’s why the answer to your question is “no” — you can’t just delete a partition and keep its data. "The original HDFS uses of many local disks on the cluster. DROP TABLE removes metadata and data for this table. 08:35 AM. Write a script which can execute below statement for all the tables that are in warehouse directory. "The original HDFS uses of many local disks on the cluster. It is used to querying and managing large datasets residing in distributed storage. You could refer the following article:
Could you share the describe formatted output from your table? Hi,Here is the script: https://github.com/Naveen3Singh/drop_db-tableThanks for Watching!Bye The container contains a bunch of text files. Now table will be droped and files from HDFS path will be removed. Hive; HIVE-86; drop table should not delete data for external tables. So one should be careful while using internal tables as one drop command can destroy the whole data. 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. Created That’s why they are called hive managed table and hive owns data. 06-29-2018 table structure is dropped from the schema but the underlying HDFS file is not. (NOT WORKING) Note : In all the above cases, skipTrash is set in hive library. Using cascade, you can delete this database directly (without deleting its contents manually) as shown below. Update and delete statements modify and delete values already written to Hive. HDInsight uses Azure Blob storage instead for data storage. This tells you a DROP TABLE spark_hive_test_yarn_cluster_table command was executed at 2016-03-01 around UTC time 23:47:14. The data will be located in a folder named after the table within the Hive data warehouse, which is essentially just a file location in HDFS. Apache Hive is a Data warehouse system which is built to work on Hadoop. If you really need to clean up your data plus structure then to guarantee, I'd drop the table and truncate it. From the following screenshot, we can observe the output In above code and from screen shot we do following things, Usually, the problem does not repeat itself when trying to recreate the same tables under different names, but I don't think it's a good solution to create hundreds of tables ala table1, ..., table506 to be able to work with the file.. Ex: UseCase 1: 1. The data is actually moved to the .Trash/Current directory if Trash is configured (and PURGE is not specified). 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. Click Delete in the UI. Drop the table tab1. That’s why they are called hive managed table and hive owns data. Could you please confirm if you are using managed or external table? An external table can be created when data is not present in any existing table (i.e., using the SELECT clause). Follow below steps to remove columns from Hive table using intermediate or temporary tables. hadoop,apache-hive. Then we can drop the current hive database. Created While running the same data step again (after deletion), i,e. hive> drop table ; //now the table is internal if you drop the table data will be dropped automatically. An external table means the data is managed separately from the metadata associated with it. This is part 1 of a 2 part series for how to update Hive Tables the easy way Historically, keeping data up-to-date in Apache Hive required custom application development that is complex, non-performant […] We loaded data into it and realized that hive will create appropriate directory and copy files into those directories. The following query drops the database using CASCADE. See Also-Different Ways to Configure Hive Metastore The location is user-configurable when Hive is installed. student_id INT,
As far as I know, the table is not external, it is created by joining multiple other tables. By default, SAS data step option DBCREATE_EXTERNAL is set to NO which means SAS data step using hive libraries like below creates a “managed table”. We saw un-partitioned and partitioned tables. External Tables : Hive does not move the data into its warehouse directory. Hive>LOAD DATA INPATH '/user/guru99hive/data.txt' INTO table guruhive_internaltable; 3. Steps Sort By Name; Sort By Date; Ascending; Descending; Attachments. I can suceessfully drop hive table in hive cli / beeline so no permission issue.