Big Data and PostgreSQL

© 2ndQuadrant 2016

Big Data & PostgreSQLUsing TABLESAMPLE to Analyze

Very Large Datasets

By Umair Shahid

© 2ndQuadrant 2016

Who am I?● Got “pushed” into PostgreSQL in 2004, ended

up falling in love with it● Not a hardcore techie, yet passionate about

open source software● Heading the productization efforts at

2ndQuadrant● Interested in Big Data, specifically the newer

PostgreSQL features supporting it

© 2ndQuadrant 2016

What is the problem?Number of Rows Size on Disk (MB) Time Taken (ms)

1k 0.23 219.706

100k 24 1,302.135

1M 195 7,696.386

5M 951 40,691.603

10M 1,923 60,012.457

100M 19,456 801,493.319

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Why is this significant?

● Data mining has typically been a painful process● Major contributor to the pain has been the time it

takes for queries to return● Many false steps before the required data is

identified● Waiting time is wasted time● Sampling, count based or time based, reduces

the wasted time significantly

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What is TABLESAMPLE?

● Ability to read a random sample of data in a table

● Defined in SQL:2003 (5th revision of SQL)

● Implemented in PostgreSQL 9.5

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Syntax

SELECT select_expression

FROM table_name

TABLESAMPLE sampling_method ( argument [, ...] )

[ REPEATABLE ( seed ) ]

...

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sampling_method

● argument is percentage of rows● SYSTEM

○ Block level sampling○ Very fast○ Non-independent rows

● BERNOULLI○ Row level sampling○ Slower than SYSTEM○ Independent rows (uniformly random)

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Demo sampling methods

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REPEATABLE results● (Reminder: [ REPEATABLE ( seed ) ])● Optional argument● Used if random, yet repeatable results are

required● seed and argument need to be the same to

produce repeatable results● Any changes made to the table will result in a

different data set

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Now it gets interesting … ● TABLESAMPLE allows for additional sampling methods

via extensions● tsm_system_time specifies max number of

milliseconds to spend reading a table● Implements the syntax:

SELECT select_expression

FROM table_name

TABLESAMPLE SYSTEM_TIME (argument)

© 2ndQuadrant 2016

Enter Orange ...● Funded by AXLE (http:

//axleproject.eu)● Same project funded

TABLESAMPLE● Available integrated

with PostgreSQL in 2UDA (http://2ndquadrant.com/2uda)

● Uses TABLESAMPLE to very quickly create visualizations for data

● Can quickly create predictive models

http://axleproject.eu



http://2ndquadrant.com/2uda




© 2ndQuadrant 2016

Other Big Data features in PostgreSQL

● JSON & JSONB● HSTORE● XML● Scale-out by partitioning

○ Check out Postgres-XL (http://www.postgres-xl.org/)

● etc ...

http://www.postgres-xl.org/



© 2ndQuadrant 2016

Umair ShahidEmail: [email protected]

Twitter: @pg_umair

2ndQuadrant is hiring - All geographies!

Thank you for your time!

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Big Data and PostgreSQL

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