Introduction to Apache Hive | Big Data Hadoop Spark Tutorial | CloudxLab

Hive
Hive - Introduction
● Data warehouse infrastructure tool
● Process structured data in Hadoop
● Resides on top of Hadoop
● Makes data churning easy
● Provides SQL like queries

Hive
Why Do We Need Hive?
● Developers face problem in writing MapReduce logic
● How to port existing
○ relational databases
○ SQL infrastructure with Hadoop?
● End users are familiar with SQL queries than MapReduce
and Pig
● Hive’s SQL-like query language makes data churning easy

Hive
Hive - Components
Hive
MapReduce
YARN
HiveServer2
Port - 10000

Hive
Hive - Limitations
• Does not provide row level updates (earlier
versions)
• Not suitable for OLTP
• Queries have higher latency
• Start-up overhead for MapReduce jobs
• Best when large dataset is maintained and mined

Hive
Hive - Data Types - Numeric
● TINYINT (1-byte signed integer)
● SMALLINT (2-byte signed integer)
● INT (4-byte signed integer)
● BIGINT (8-byte signed integer)
● FLOAT (4-byte single precision floating point number)
● DOUBLE (8-byte double precision floating point number)
● DECIMAL (User defined precisions)

Hive
Hive - Data Types - Date/Time
● TIMESTAMP ( Hive version > 0.8.0 )
● DATE ( Hive version > 0.12.0 ) - YYYY-MM-DD

Hive
Hive - Data Types - String
● STRING
● VARCHAR ( Hive version > 0.12.0 )
● CHAR ( Hive version > 0.13.0 )

Hive
Hive - Data Types - Misc
● BOOLEAN
● BINARY ( Hive version > 0.8.0 )

Hive
Hive - Data Types - Complex
arrays: ARRAY<data_type>
maps: MAP<primitive_type, data_type>
structs: STRUCT<col_name : data_type [COMMENT col_comment], ...>
union: UNIONTYPE<data_type, data_type, ...> ( Hive version > 0.7.0 )

Hive
Hive - Data Types - Example
CREATE TABLE employees(
name STRING,
salary FLOAT,
subordinates ARRAY<STRING>,
deductions MAP<STRING, FLOAT>,
address STRUCT<street:STRING,
city:STRING,
state:STRING,
zip:INT>,
auth UNION<fbid:INT, gid:INT, email:STRING>
)

Hive
name STRING,
salary FLOAT,
city:STRING,
state:STRING,
zip:INT>,
)
“John”

Hive
name STRING,
salary FLOAT,
city:STRING,
state:STRING,
zip:INT>,
)
40000.00

Hive
name STRING,
salary FLOAT,
city:STRING,
state:STRING,
zip:INT>,
)
[“Michael”, “Rumi”]

Hive
name STRING,
salary FLOAT,
city:STRING,
state:STRING,
zip:INT>,
)
{
“Insurance”: 500.00,
“Charity”: 600.00
}

Hive
name STRING,
salary FLOAT,
city:STRING,
state:STRING,
zip:INT>,
)
“street” : “2711”,
“city”: “Sydney”,
“state”: “Wales”,
“zip”: 560064

Hive
name STRING,
salary FLOAT,
city:STRING,
state:STRING,
zip:INT>,
)
“fbid”:168478292

Hive
• Stores the metadata of tables into a relational database
• Metadata includes
• Details of databases and tables
• Table definitions: name of table, columns, partitions etc.
Hive - Metastore

Hive
Hive - Warehouse
● Hive tables are stored in the Hive warehouse
directory
● /apps/hive/warehouse on HDFS
● At the location specified in the table definition

Hive
Hive - Getting Started - Command Line
● Login to CloudxLab Linux console
● Type “hive” to access hive shell
● By default database named “default” will be selected as current
db for the current session
● Type “SHOW DATABASES” to see list of all databases

Hive
● “SHOW TABLES” will list tables in current selected database
which is “default” database.
● Create your own database with your login name
● CREATE DATABASE abhinav9884;
● DESCRIBE DATABASE abhinav9884;
● DROP DATABASE abhinav9884;

Hive
● CREATE DATABASE abhinav9884;
● USE abhinav9884;
● CREATE TABLE x (a INT);

Hive
Hive - Getting Started - Hue
● Login to Hue
● Click on “Query Editors” and select “Hive”
● Select your database (abhinav9984) from the list
● SELECT * FROM x;
● DESCRIBE x;
● DESCRIBE FORMATTED x;

Hive
Hive - Tables
● Managed tables
● External tables

Hive
Hive - Managed Tables
● Aka Internal
● Lifecycle managed by Hive
● Data is stored in the warehouse directory
● Dropping the table deletes data from warehouse

Hive
● The lifecycle is not managed by Hive
● Hive assumes that it does not own the data
● Dropping the table does not delete the underlying data
● Metadata will be deleted
Hive - External Tables

Hive
Hive - Managed Tables - Example
CREATE TABLE nyse(
exchange1 STRING,
symbol1 STRING,
ymd STRING,
price_open FLOAT,
price_high FLOAT,
price_low FLOAT,
price_close FLOAT,
volume INT,
price_adj_close FLOAT
)
ROW FORMAT DELIMITED FIELDS TERMINATED BY 't';
DESCRIBE nyse;
DESCRIBE FORMATTED nyse;

Hive
Hive - Loading Data - From Local Directory
● hadoop fs -copyToLocal /data/NYSE_daily
● Launch Hive
● use yourdatabase;
● load data local inpath 'NYSE_daily' overwrite into table nyse;
● Copies the data from local file system to warehouse

Hive
CREATE TABLE nyse_hdfs(
exchange1 STRING,
symbol1 STRING,
ymd STRING,
price_open FLOAT,
price_high FLOAT,
price_low FLOAT,
price_close FLOAT,
volume INT,
)
ROW FORMAT DELIMITED FIELDS TERMINATED BY 't';
Hive - Loading Data - From HDFS

Hive
Hive - Loading Data - From HDFS
● Copy /data/NYSE_daily to your home directory in HDFS
● load data inpath 'hdfs:///user/abhinav9884/NYSE_daily' overwrite into table
nyse_hdfs;
● Moves the data from specified location to warehouse
● Check if NYSE_daily is in your home directory in HDFS

Hive
Hive - External Tables
CREATE EXTERNAL TABLE nyse_external (
exchange1 STRING,
symbol1 STRING,
ymd STRING,
price_open FLOAT,
price_high FLOAT,
price_low FLOAT,
price_close FLOAT,
volume INT,
)
ROW FORMAT DELIMITED FIELDS TERMINATED BY 't'
LOCATION '/user/abhinav9884/NYSE_daily';
describe formatted nyse_external;

Hive
Hive - S3 Based External Table
create external table miniwikistats (
projcode string,
pagename string,
pageviews int,
bytes int)
partitioned by(dt string)
row format delimited fields terminated by ' '
lines terminated by 'n'
location 's3n://paid/default-datasets/miniwikistats/';

Hive
Hive - Select Statements
● Select all columns
SELECT * FROM nyse;
● Select only required columns
SELECT exchange1, symbol1 FROM nyse;

Hive
● Find average opening price for each stock
SELECT symbol1, AVG(price_open) AS avg_price FROM nyse
GROUP BY symbol1;
● To improve performance set top-level aggregation in map phase
SET hive.map.aggr=true;
Hive - Aggregations

Hive
Hive - Saving Data
● In local file system
insert overwrite local directory '/home/abhinav9884/onlycmc'
select * from nyse where symbol1 = 'CMC';
● In HDFS
insert overwrite directory 'onlycmc' select * from nyse where
symbol1 = 'CMC';

Hive
Hive - Tables - DDL - ALTER
● Rename a table
ALTER TABLE x RENAME TO x1;
● Change datatype of column
ALTER TABLE x1 CHANGE a a FLOAT;
● Add columns in existing table
ALTER TABLE x1 ADD COLUMNS (b FLOAT, c INT);

Hive
#First name, Department, Year of joining
Mark, Engineering, 2012
Jon, HR, 2012
Monica, Finance, 2015
Steve, Engineering, 2012
Michael, Marketing, 2015
Hive - Partitions

Hive
● Data is located at /data/bdhs/employees/ on HDFS
● Copy data to your home directory in HDFS
hadoop fs -cp /data/bdhs/employees .
● Create table
name STRING,
department STRING,
somedate DATE
)
PARTITIONED BY(year STRING)
ROW FORMAT DELIMITED FIELDS TERMINATED BY ',';
Hive - Partitions - Hands-on

Hive
● Load dataset 2012.csv
load data inpath 'hdfs:///user/sandeepgiri9034/employees/2012.csv' into table
employees partition (year=2012);
● Load dataset 2015.csv
load data inpath 'hdfs:///user/sandeepgiri9034/employees/2015.csv' into table
employees partition (year=2015);
● SHOW PARTITIONS employees;
● Check warehouse and metastore
Hive - Partitions - Hands-on

Hive
• To avoid the full table scan
• The data is stored in different files in warehouse defined by the
partitions
• Define the partitions using “partition by” in “create table”
• We can also add a partition later
• Partition can happen on multiple columns (year=2012, month=10,
day=12)
Hive - Partitions - Summary

Hive
● SELECT * FROM employees where department='Engineering';
● Create a view
CREATE VIEW employees_engineering AS
SELECT * FROM employees where department='Engineering';
● Now query from the view
SELECT * FROM employees_engineering;
Hive - Views

Hive
• Allows a query to be saved and treated like a table
• Logical construct - does not store data
• Hides the query complexity
• Divide long and complicated query into smaller and manageable
pieces
• Similar to writing a function in a programming language
Hive - Views - Summary

Hive
Hive - Load JSON Data
• Download JSON-SERDE BINARIES
• ADD JAR
hdfs:///data/serde/json-serde-1.3.6-SNAPSHOT-jar-with-dependencies.jar;
• Create Table
CREATE EXTERNAL TABLE tweets_raw (
)
ROW FORMAT SERDE 'org.apache.hive.hcatalog.data.JsonSerDe'
LOCATION '/user/abhinav9884/senti/upload/data/tweets_raw';

Hive
ORDER BY x
● Guarantees global ordering
● Data goes through just one reducer
● This is unacceptable for large datasets as it will overload the
reducer
● You end up one sorted file as output
Hive - Sorting & Distributing - Order By

Hive
SORT BY x
● Orders data at each of N reducers
● Number of reducers are 1 per 1GB
● You end up with N or more sorted files with overlapping ranges
Hive - Sorting & Distributing - Sort By

Hive
Hive - Sorting & Distributing - Sort By
Aaron
Bain
Adam
Barbara
Reducer 1 Reducer 2
Aaron
Bain
Adam
Barbara
Concatenated File

Hive
DISTRIBUTE BY x
● Ensures each of N reducers gets non-overlapping ranges of x
● But doesn't sort the output of each reducer
● You end up with N or unsorted files with non-overlapping ranges
Hive - Sorting & Distributing - Distribute By

Hive
Hive - Sorting & Distributing - Distribute By
Adam
Aaron
Barbara
Bain
Reducer 1 Reducer 2

Hive
CLUSTER BY x
● Gives global ordering
● Is the same as (DISTRIBUTE BY x and SORT BY x)
● CLUSTER BY is basically the more scalable version of ORDER BY
Hive - Sorting & Distributing - Cluster By

Hive
Hive - Bucketing
CREATE TABLE page_view(viewTime INT, userid BIGINT,
page_url STRING, referrer_url STRING,
ip STRING COMMENT 'IP Address of the User'
)
COMMENT 'This is the page view table'
PARTITIONED BY(dt STRING, country STRING)
CLUSTERED BY(userid) INTO 32 BUCKETS
ROW FORMAT DELIMITED FIELDS TERMINATED BY '001'
COLLECTION ITEMS TERMINATED BY '002'
MAP KEYS TERMINATED BY '003'
STORED AS SEQUENCEFILE;

Hive
● Optimized Row Columnar file format
● Provides a highly efficient way to store Hive data
● Improves performance when
○ Reading
○ Writing
○ Processing
● Has a built-in index, min/max values, and other aggregations
● Proven in large-scale deployments
○ Facebook uses the ORC file format for a 300+ PB deployment
Hive - ORC Files

Hive
Hive - ORC Files - Example
CREATE TABLE orc_table (
first_name STRING,
last_name STRING
) STORED AS ORC;
INSERT INTO orc_table VALUES('John', 'Gill');
SELECT * from orc_table;
To Know more, please visit https://orc.apache.org

Hive
Hive - Quick Recap
• Each table has got a location
• By default the table is in a directory under the location
/apps/hive/warehouse
• We can override that location by mentioning 'location' in create table
clause
• Load data copies the data if it is local
• Load moves the data if it is on hdfs for both external and managed
tables
• Dropping managed table deletes the data at the 'location'
• Dropping external table does not delete the data at the 'location'
• The metadata is stored in the relational database - hive metastore

Hive
Hive - Connecting to Tableau
• Tableau is a visualization tool
• Tableau allows for instantaneous insight by transforming data into
visually appealing, interactive visualizations called dashboards

Hive
Hive - Connecting to Tableau - Steps
• Download and install Tableau desktop from
https://www.tableau.com/products/desktop
• Download and install Hortonworks ODBC driver for Apache Hive for
your OS
https://hortonworks.com/downloads/

Hive
Hive - Connecting to Tableau - Hands-on
Visualize top 10 stocks with highest opening price on Dec 31, 2009

Hive
1. Copy data from /data/ml100k/u.data into our hdfs home
2. Open Hive in Hue and run following:
CREATE TABLE u_data( userid INT, movieid INT, rating INT, unixtime STRING)
ROW FORMAT DELIMITED
FIELDS TERMINATED BY 't'
STORED AS TEXTFILE;
LOAD DATA INPATH '/user/sandeepgiri9034/u.data' overwrite into table u_data;
select * from u_data limit 5;
select movieid, avg(rating) ar from u_data group by movieid order by ar desc
Hive - Quick Demo

Hive
Hive - Quick Demo
Join with Movie Names
create view top100m as
select movieid, avg(rating) ar from u_data group by movieid order by ar desc
CREATE TABLE m_data( movieid INT, name STRING)
ROW FORMAT DELIMITED
FIELDS TERMINATED BY '|'
STORED AS TEXTFILE;
load data inpath '/user/sandeepgiri9034/u.item' into table m_data;
select * from m_data limit 100
select * from m_data, top100m where top100m.movieid = m_data.movieid

Hive
1. For each movie how many users rated it
2. For movies having more than 30 ratings, what is
the average rating
Hive - Assignment

Introduction to Apache Hive | Big Data Hadoop Spark Tutorial | CloudxLab

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