HIVE

Introduction

• Data ware housing tool on top of Hadoop
• SQL like interface
• Provides SQL like language to analyze the data stored on HDFS
• Can be used by people who know SQL
• Not all traditional SQL capabilities are supported
• Under the hood hive queries are executed as MapReduce jobs
• No extra work is required

Hive Components

• MetaStore
• Its a database consisting of table definitions and other metadata
• By default stored on the local machine on derby database
• It can be kept on some shared machine like relational data base if multiple users are using

Query Engine

• Hive-QL which gives SQL like query
• Internally Hive queries are run as map reduce job

Hive Data Models

• Hive forns or layers table definitions on top of data residing on HDFS

Databases

• Name space that separates tables from other units from naming confliction

Table

• Homogenous unit of data having same schema

MetaStore

Its a data base consisting of table definations and other metadata. By default stored on the local  machine on derby database. It can be kept on some shared machine like relational data base if multiple users are using.

Before you start installing hive, you should have already installed hadoop.

See Hadoop Installation

Step 1: Download Hive from apache website (check with comparability with hadoop version)

Step 2: Go to downloads and extract hive.tar.gz

Step 3: Copy the extracted jar into /home/hduser/hive.

Step 4: Edit /etc/bash.bashrc

                $gedit bash.bashrc

                $sudo gedit  /etc/bash.bashrc

                $sudo leafpad /etc/bash.bashrc

Step 5: Set Home Path

                export HADOOP_HOME=/home/hduser/hadoop

                export HIVE_HOME=/home/hduser/hive

                export PATH=$PATH:$HADOOP_HOME/bin

                export PATH=$PATH:$HIVE_HOME/bin

Step 6: Save and Close

Step 7: Open terminal and enter hive 

Now you can enter hive shell.