The Hive metastore is a central repository that stores metadata information about Hive tables, including the table schema, column names, column types, storage format, and location of the data. The Hive metastore plays a crucial role in enabling Hive to interact with data stored in various storage systems, such as HDFS, S3, and others.
When a user creates a table in Hive, the metastore stores the metadata about the table, such as its schema and storage format. When a user queries the table, Hive retrieves this metadata from the metastore to determine how to read the table’s data. The metastore also tracks the location of the table data and manages the mapping of the table schema to the physical storage format.
In addition to table metadata, the Hive metastore also stores information about other objects in Hive, such as databases, views, and partitions.
The Hive metastore can be implemented using various databases, such as MySQL, PostgreSQL, or Oracle. By default, Hive uses an embedded Derby database to store the metastore. However, for production use cases, it is recommended to use an external database to store the metastore for better performance, scalability, and reliability.
In summary, the Hive metastore plays a critical role in enabling Hive to manage and query data stored in various storage systems by storing and managing metadata about the Hive tables and other objects.