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Date: Mon, 25 Feb 2013 18:52:59 +0900
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Subject: [PROPOSAL] Tajo (A Data Warehouse System for Hadoop) to join Apache
 Incubator
From: Hyunsik Choi <hyunsik@apache.org>
To: general@incubator.apache.org
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Hi folks,

I would like to propose Tajo to the Apache incubator.

http://wiki.apache.org/incubator/TajoProposal

Tajo is a distributed data warehouse system for Hadoop. Tajo is designed
for low-latency and scalable ad-hoc queries, online aggregation and ETL on
large-data sets by leveraging advanced database techniques. It supports SQL
standards. Tajo uses HDFS as a primary storage layer, uses Apache Hadoop
Yarn as a resource management platform, and has its own query engine which
enables direct control of distributed execution and data flow. Tajo is in
the alpha stage, and its initial code contains about 100,000 lines.

I are looking forward to your feedback and suggestions.

Thanks,
Hyunsik Choi

------------------------------------------------------------------------

= Abstract =

Tajo is a distributed data warehouse system for Hadoop.

= Proposal =
Tajo is a relational and distributed data warehouse system for Hadoop. Tajo
is designed for low-latency and scalable ad-hoc queries, online aggregation
and ETL on large-data sets by leveraging advanced database techniques. It
supports SQL standards. Tajo is inspired by Dryad, MapReduce, Dremel,
Scope, and parallel databases. Tajo uses HDFS as a primary storage layer,
and it has its own query engine which allows direct control of distributed
execution and data flow. As a result, Tajo has a variety of query
evaluation strategies and more optimization opportunities. In addition,
Tajo will have a native columnar execution and and its optimizer. Tajo will
be an alternative choice to Hive/Pig on the top of MapReduce.

= Background =
Big data analysis has gained much attention in the industrial. Open source
communities have proposed scalable and distributed solutions for ad-hoc
queries on big data. However, there is still room for improvement. Markets
need more faster and efficient solutions. Recently, some alternatives
(e.g., Cloudera's Impala and Amazon Redshift) have come out.

= Rationale =
There are a variety of open source distributed execution engines (e.g.,
hive, and pig) running on the top of MapReduce. They are limited by MR
framework. They cannot directly control distributed execution and data
flow, and they just use MR framework. So, they have limited query
evaluation strategies and optimization opportunities. It is hard for them
to be optimized for a certain type of data processing.

= Initial Goals =

The initial goal is to write more documents to describe Tajo's internal. It
will be helpful to recruit more committers and to build a solid community.
Then, we will make milestones for short/long term plans.

= Current Status =

Tajo is in the alpha stage. Users can execute usual SQL queries (e.g.,
selection, projection, group-by, join, union and sort) except for nested
queries. Tajo provides various row/column storage formats, such as CSV,
RowFile (a row-store file we have implemented), RCFile, and Trevni, and it
also has a rudimentary ETL feature to transform one data format to another
data format. In addition, Tajo provides hash and range repartitions. By
using both repartition methods, Tajo processes aggregation, join, and sort
queries over a number of cluster nodes. To evaluate the performance, we
have carried out benchmark test using TPC-H 1TB on 32 cluster nodes.

== Meritocracy ==

We will discuss the milestone and the future plan in an open forum. We plan
to encourage an environment that supports a meritocracy. The contributors
will have different privileges according to their contributions.

== Community ==
Big data analysis has gained attention from open source communities,
industrial and academic areas. Some projects related to Hadoop already have
very large and active communities. We expect that Tajo also will establish
an active community. Since Tajo already works for some features and is in
the alpha stage, it will attract a large community soon.

== Core Developers ==
Core developers are very experienced in the Apache Hadoop ecosystem. To
achieve more diversity of developers, we will be eager to recruit
developers from diverse companies.
* Eli Reisman <ereisman AT apache DOT org>
* Hyunsik Choi <hyunsik AT apache DOT org>
* Jihoon Son <ghoonson AT gmail DOT com>
* Jin Ho Kim <jhkim AT gruter DOT com>
* Sangwook Kim <swkim AT inervit DOT com>

== Alignment ==
Tajo employs Apache Hadoop Yarn as a resource management platform for large
clusters. It uses HDFS as a primary storage layer. It already supports
Hadoop-related data formats (RCFile, Trevni) and will support ORC file. In
addition, we have a plan to integrate Tajo with other products of Hadoop
ecosystem. Tajo's modules are well organized, and these modules can also be
used for other projects.

= Known Risks =

== Orphaned Products ==
Most of codes have been developed by only two core developers, who are
Hyunsik Choi and Jihoon Son. It may be a risk of being orphaned. However,
they are guaranteed to have enough time to develop Tajo for years. As you
can see the commit history, they have participated in this project for
about two years. Recently, Tajo has been supported by two IT companies in
Korea. So, the risk of being orphaned is relatively low. In addition, we
will be eager to recruit additional committers in order to eliminate this
risk.

== Inexperience with Open Source ==
Most of the initial committers have experience working on open source
projects. Eli Reisman and Hyunsik Choi have experience as committers and
PMC members on other Apache projects.

== Homogeneous Developers ==
Although they have four affiliations, what most of core developers are in
South Korea is a risk. This is because their offline activities are limited
due to their location. Since we surely recognize this risk, we will write
more complete documents and presentation materials in order to disseminate
Tajo's internal and users guide. In addition, to mitigate this risk we will
be eager to recruit additional committers around the world.

== Reliance on Salaried Developers ==
It is expected that Tajo development will occur on both salaried time and
on volunteer time. Hyunsik Choi and Jihoon Son belong to Database lab.,
Korea Univ. They will be paid by the lab to contribute Tajo for years. Jin
Ho Kim and Sangwook Kim are paid by their employer to contribute to this
project. Eli Reisman will contribute to this project on volunteer time. In
addition, we will be eager to recruit additional committers including
salaried and non-salaried developers.

== Relationships with Other Apache Products ==
Tajo has some overlapping function with Apache Incubator Drill. However,
Tajo is more mature than Drill. In addition, there are some significant
differences. Drill is a distributed system specialized for low-latency
query processing by using column operations and intermediate data
streaming. Drill has very simple query optimizer. However, some queries
including big-big table join and sort are not available in that manner.
Drill will support some of query types.

In contrast, Tajo has advanced query optimization system. Tajo mainly aims
at scalable and efficient processing on all query types. By using the query
optimizer, Tajo will only chase low latency query processing for some query
types that can be executed in online aggregation manner.

Besides, Tez has some overlapping functions with Tajo. However, Tez is in
the pre-alpha stage and may be a prototype. When Tez becomes feasible, Tajo
could use Tez as an underlying framework according to the applicability.
However, Tajo will still use its row/native columnar execution engine and
its optimizer. Tajo may be potentially the first application of Tez.

== A Excessive Fascination with the Apache Brand ==
We believe that the Apache brand will help us to find contributors and to
grow the community. The community and development process will make this
project more stable and help establish ubiquitous APIs. In addition, Tajo
depends other project in Apache Hadoop ecosystem. We expect that
cooperative work occurs with other projects in the same place.

= Documentation =
Tajo's demonstration paper was accepted to IEEE ICDE 2013. Since this
conference will be held in April 2013, we cannot publicly show the paper.
Instead, we attached some presentation material. Checkout this slide (
http://www.slideshare.net/hyunsikchoi/tajo-intro)

In addition, some documents (e.g., getting started) are available at
http://tajo-project.github.com/tajo/

= Initial Source =
The initial source code has been developed in the Database Lab. Korea Univ.
This has been implemented in Java and has almost 100,000 lines except for
parser and protobuf generated codes. Currently, initial source code is
already available on GitHub at https://github.com/tajo-project/tajo.

= Source and Intellectual Property Submission Plan =

We intend the entire code base to be licensed under the Apache License,
Version 2.0.

= External Dependencies =
The required dependencies are all Apache compatible licenses. The following
components with non-Apache licenses are enumerated:

* Google Guava
* Google Protocol Buffer
* Antlr
* Mockito
* JLine2

= Cryptography =

Tajo will depend on secure Hadoop that can optionally use Kerberos.

= Required Resources =
== Mailling List ==
* tajo-private (with moderated subscriptions)
* tajo-dev
* tajo-commits
* tajo-user

== Subversion Directory ==
https://git-wip-us.apache.org/repos/asf/tajo.git

== Issue Tracking ==
Jira Tajo (TAJO)

== Other Resources ==
* Continuous Integration
* Jenkins
* Wiki
* http://wiki.apache.org/tajo

= Initial Committers =
* Eli Reisman <ereisman AT apache DOT org>
* Hyunsik Choi <hyunsik AT apache DOT org>
* Jihoon Son <ghoonson AT gmail DOT com>
* Jin Ho Kim <jhkim AT gruter DOT com>
* Sangwook Kim <swkim AT inervit DOT com>

= Affiliations =
* Eli Reisman (Hortonworks)
* Hyunsik Choi (Database Lab., Korea University)
* Jihoon Son (Database Lab., Korea University)
* Jin Ho Kim (Gruter)
* Sangwook Kim (Inervit)

The nominated mentors are employees of Hortonworks and NASA JPL.

* Chris Mattman - NASA JPL
* Jakob Homan - LinkedIn
* Owen O'Malley - Hortonworks

= Sponsors =

== Champion ==

* Jakob Homan <ghoman AT apache DOT org>

== Nominated Mentors ==

* Chris Mattman <chris DOT a DOT mattmann AT jpl DOT nasa DOT gov>
* Jakob Homan <jghoman AT apache DOT org>
* Owen O'Malley <omalley AT apache DOT org>

== Sponsoring Entity ==
Apache Incubator

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