When use managed table and external table in hive?

Asked By: Raja Dollt | Last Updated: 5th February, 2020
Category: hobbies and interests beekeeping
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Managed table is also called as Internal table. This is the default table in Hive. When we create a table in Hive without specifying it as external, by default we will get a Managed table. If we create a table as a managed table, the table will be created in a specific location in HDFS.

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Furthermore, what is difference between external table and managed table in hive?

when we create a table in HIVE, HIVE by default manages the data and saves it in its own warehouse, where as we can also create an external table, which is at an existing location outside the HIVE warehouse directory. The main difference between these two types of tables is seen during LOAD and DROP statements.

Also, can we convert external table to managed table in hive? It depends on use case basis. Typically external tools push data in hdfs and external tables are created on the same. For further transformation, processing , new data set created from external table can be moved to managed table.

Also, what are managed and external tables in hive?

There are two types of tables in Hive ,one is Managed table and second is external table. the difference is , when you drop a table, if it is managed table hive deletes both data and meta data,if it is external table Hive only deletes metadata. by default It is Managed table .

When would you choose to create an external Hive table?

We create an external table for external use as when we want to use the data outside the Hive. External tables are stored outside the warehouse directory. They can access data stored in sources such as remote HDFS locations or Azure Storage Volumes.

39 Related Question Answers Found

What is a managed table?

A managed table is also called an Internal table. This is the default table in Hive. When we create a table in Hive without specifying it as external, by default we will get a Managed table. If we create a table as a managed table, the table will be created in a specific location in HDFS.

Can we insert data into Hive external table?

Hive can insert data into multiple tables by scanning the input data just once. SELECT firstname,lastname WHERE country='US'; Create an external table that points to a HDFS directory containing the data file.

How do you know if a hive table is external?

For external tables Hive assumes that it does not manage the data. Managed or external tables can be identified using the DESCRIBE FORMATTED table_name command, which will display either MANAGED_TABLE or EXTERNAL_TABLE depending on table type.

Why do we need external table in hive?

It is called EXTERNAL because the data in the external table is specified in the LOCATION properties instead of the default warehouse directory. When keeping data in the internal tables, Hive fully manages the life cycle of the table and data. This means the data is removed once the internal table is dropped.

What is an external table?

An external table is a table whose data come from flat files stored outside of the database. Oracle can parse any file format supported by the SQL*Loader.

How do I update hive external table?

There are many approaches that you can follow to update Hive tables, such as:
  1. Use Temporary Hive Table to Update Table.
  2. Set TBLPROPERTIES to enable ACID transactions on Hive Tables.
  3. Use HBase to update records and create Hive External table to display HBase Table data.

How do I create a hive table from a CSV file?

Solution
  1. Step 1: Sample CSV File. Create a sample CSV file named as sample_1.
  2. Step 2: Copy CSV to HDFS. Run Below commands in the shell for initial setup.
  3. Step 3: Create temporary Hive Table and Load data.
  4. Step 4: Verify data.
  5. Step 5: Create an ORC table.
  6. Step 6: Copy data from a temporary table.
  7. Step 6: Output.

How do I delete data from hive external table?

For external table, the simple way is to change the table from external to internal and then Drop table, data will be deleted as well:
  1. ALTER TABLE $tablename SET TBLPROPERTIES('EXTERNAL'='False');
  2. Drop table $table.

Where is data stored in hive?

2 Answers. Hive data are stored in one of Hadoop compatible filesystem: S3, HDFS or other compatible filesystem. Hive metadata are stored in RDBMS like MySQL. The location of Hive tables data in S3 or HDFS can be specified for both managed and external tables.

What is hive used as?

Hive is an ETL and data warehouse tool on top of Hadoop ecosystem and used for processing structured and semi structured data. Hive is a database present in Hadoop ecosystem performs DDL and DML operations, and it provides flexible query language such as HQL for better querying and processing of data.

What is ORC table in hive?

ORC stands for Optimized Row Columnar which means it can store data in an optimized way than the other file formats. An ORC file contains rows data in groups called as Stripes along with a file footer. ORC format improves the performance when Hive is processing the data.

What is create external table in hive?

Hive Create External Tables and Examples. A Hive external table allows you to access external HDFS file as a regular managed tables. You can join the external table with other external table or managed table in the Hive to get required information or perform the complex transformations involving various tables.

What happens when an external table is dropped in hive?

Drop Hive external table WITHOUT removing data. The goal is to destroy a Hive schema but keep the data underneath. This deletes the data (removes the folder /user/me/data/ ). This folder has to remain for use in other projects.

What is Metastore?

Metastore is the central repository of Hive Metadata. It stores the meta data for Hive tables and relations. For example, Schema and Locations etc.

What is the difference between static and dynamic partitioning in hive?

Partitions are created when data is inserted into table. Usually when loading files (big files) into Hive tables static partitions are preferred. That saves your time in loading data compared to dynamic partition. You "statically" add a partition in table and move the file into the partition of the table.

What is MSCK repair table hive?

MSCK REPAIR TABLE. Use this statement on Hadoop partitioned tables to identify partitions that were manually added to the distributed file system (DFS). This statement (a Hive command) adds metadata about the partitions to the Hive catalogs.