Why Hive uses Metastore?

Why Hive uses Metastore?

Metastore is the central repository of Apache Hive metadata. It stores metadata for Hive tables (like their schema and location) and partitions in a relational database. It provides client access to this information by using metastore service API.

How will you decide the cluster size when setting up a Hadoop cluster?

1 Answer

  1. Bare minimum, depending on replication factor of 3, you need about 50TB (10×3=30TB 80\% rule: 40TB usable, this give you 8TB to work with ) – So 5 Nodes at 10TB a piece for HDFS.
  2. HDFS can only use a maximum of 80\% of total cluster space.
  3. More nodes = faster YARN jobs.

What does hive Metastore contain?

Hive metastore (HMS) is a service that stores metadata related to Apache Hive and other services, in a backend RDBMS, such as MySQL or PostgreSQL. Impala, Spark, Hive, and other services share the metastore. The connections to and from HMS include HiveServer, Ranger, and the NameNode that represents HDFS.

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Why is Hive metadata not stored in HDFS?

Q) Why does Hive not store metadata information in HDFS? Hive stores metadata information in the metastore using RDBMS instead of HDFS. The reason for choosing RDBMS is to achieve low latency as HDFS read/write operations are time consuming processes. Q) Whenever we run a Hive query, a new metastore_db is created.

What is hive Metastore in EMR?

A Hive metastore contains a description of the table and the underlying data making up its foundation, including the partition names and data types. Hive is one of the applications that can run on EMR.

What is hive Metastore tables?

Big SQL and Hive Metastore Introduction The Hive metastore stores the metadata for Hive tables, this metadata includes table definitions, location, storage format, encoding of input files, which files are associated with which table, how many files there are, types of files, column names, data types etc.

How can the size of a Hadoop cluster be increased Mcq?

Explanation: Adding more CPU/RAM/Disk capacity to Hadoop DataNode that is already part of a cluster does not require additional network switches.

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Where is hive Metastore stored?

By default, the location of the warehouse is file:///user/hive/warehouse and we can also use the hive-site. xml file for the local or remote metastore.

Why is Hdfs not used by Metastore for storage?

A file system like HDFS is not suited since it is optimized for sequential scans and not for random access. So, the metastore uses either a traditional relational database (like MySQL, Oracle) or file system (like local, NFS, AFS) and not HDFS.

What is Metastore DB in Hive?

All Hive implementations need a metastore service, where it stores metadata. It is implemented using tables in a relational database. By default, Hive uses a built-in Derby SQL server. It provides single process storage, so when we use Derby, we cannot run instances of Hive CLI.

What is a shared metastore in hive?

A shared metastore is a single repository that stores Hive information for all connected clusters. The information can be accessed from any of the clusters. Actual data may or may not be accessible depending on the permissions/availability of the data in that particular cluster.

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Why is my hive metastore not working in Databricks?

This is a bug that was fixed in Hive Metastore version 2.3.0 ( HIVE-12274 ). Databricks uses an earlier version of Hive Metastore (version 0.13), so this bug occurs when there is too much metadata for a column, such as an imported JSON schema. As a workaround, set up an external Hive metastore that uses version 2.3.0 or above.

How does Hadoop HDFS store HIVE data?

Hive data (not metadata) is spread across Hadoop HDFS DataNode servers. Typically, each block of data is stored on 3 different DataNodes. The NameNode keeps track of which DataNodes have which blocks of actual data. For a Hive production environment, the metastore service should run in an isolated JVM.

How to use AWS glue data catalog for hive metastore management?

Using Glue Data Catalog for Hive metastore management is very easy in EMR. Unlike on-prem setups where you need to change the value of a property in hive-site.xml, in EMR it is just a matter of a single click. Once you land on the EMR creation page, you will see a checkbox to Use AWS Glue Data Catalog for table metadata.