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What is HIVE

Hive is a data ware house system for Hadoop. It runs SQL like queries called HQL (Hive query language) which gets internally converted to map reduce jobs. Hive was developed by Facebook. Hive supports Data definition Language(DDL), Data Manipulation Language(DML) and user defined functions.

DDL: create table, create index, create views.

DML: Select, Where, group by, Join, Order By

Pluggable Functions:

UDF: User Defined Function
UDAF: User Defined Aggregate Function
UDTF: User Defined Table Function

What HIVE is not

  • Hive is not RDBMS.
  • Hive is not used for OLTP(Online Transaction Processing).
  • Even with small amount of data time to return the response can?t be compared to RDBMS.

Points to remember

  • Hive’s metastore is used to persist schema i.e. table definition(table name, columns, types), location of table files, row format of table files, storage format of files.
  • Hive Query Language is similar to SQL and gets reduced to map reduce jobs in backend.
  • Hive’s default database is derby.