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The Chinese version of my summary can be seen here : 中文版 ReadMe

SimpleDB

Database Homework of Berkeley University: Implement A Simple Database Management System，which is the same labs as MIT6.830.

You can get more details in BerkelyCS186 , MIT6.830 .

And here are two new LABS that are not in the first two sites, in which you can implement Recovery and B+Tree.

API Changes

• In Pro1, I change parameters of several methods
• In Pro3, I change the method computeCostAndCardOfSubplan() in JoinOptimizer.java in order to get a left-deep-tree(I might have found some bugs in the code provided by the course). Besides, I change the method physicalPlan() in LogicalPlan.java. Specifically, the code I added will check if the Query contains a Join, and if not, the JoinOptimizer won't be invoked.

English version of my Blog

I finished the Database Homework of Berkeley University, i.e. implementing SimpleDB, in my spare time. This blog is simply intended to share my experience and recommend the course to more friends.

Outline of the Course

The course consists of four projects that implement four core parts in the database:

Project 1: Implementing data management. This part is mainly to realize the management of data. Of course, it is necessary to set up the development environment and understand the overall framework of SimpleDB under the guidance. More specifically, it is necessary to implement storage, access and management of physical level data (binary files) and map it to logical level data (relational tables). At the end of this project, the most basic operation in SimpleDB, SeqScan, is also required. So after completing this project, you can scan the entire table.

Project 2: Implementing the operators. In this project, you will implements a series of database operators, including insert, delete, select, join, group by, order by, and so on. It is worth noting that implementing a highly efficienct version of join is the main and difficult question (but don't worry, you just need to learn some common algorithms, there are recommended articles at the end of this article). Plus, the group by and order by functions in SimpleDB have been simplified, so some work is actually saved. At the end of the project, we need to implement the cache management, a function that is not completed in project 1. You will learn and implement the caching mechanism, including the cache replacement algorithms (LRU, etc.).

Project 3: Implementing query optimization. In this project, you need to implement the cost-based optimizer. What is most difficult is to use the left-deep-tree and the idea of dynamic programming to implement the Join operation optimizer. Once completed, the performance of Filter,i.e. the SQL where clause, and Join operations will be greatly optimized.

project 4: Implementing transaction management. In this project, you need to implement transaction management of SimpleDB, including using 2PL protocol and NO STEAL/FORCE cache management strategy to enable ACID properties of transaction with page-level locking, and deadlock detection and abortion based on a simple timeout policy or cycle-detection in a dependency graph data structure (I implemented the latter one). Due to the use of NO STEAL/FORCE strategy, the log-based recovery, i.e. undo and redo functions, are omitted.

Requirement of the Course

1. The projects require few knowledge of database, but in project 4, you might have to learn some concepts of transaction management through google or relevant books. Also, the references I recommend at the end of this article might help.

2. You need to know the basic grammar of Java, and it would be better if you have learned concurrency in Java (needed in Project 4). Additionally, I change Ant (which is recommended by the course) to Maven, so if you would like to run my code, you will also need to learn some basic concept in Maven (e.g. the use of POM file).

3. It takes about one month to complete the whole four projects.

Recommended websites and books

1. https://sites.google.com/site/cs186fall2013/homeworks

This is the home page of the course, which is extremely helpful.

2. http://coding-geek.com/how-databases-work/

It is recommended to read this article before writing your code.

https://dev.mysql.com/doc/refman/5.5/en/nested-loop-joins.html

https://blog.csdn.net/ghsau/article/details/43762027 (Chinese version)

You can learn common join algorithms from this article when implementing join operator in project 2.

http://www.mathcs.emory.edu/~cheung/Courses/554/Syllabus/5-query-opt/left-deep-trees.html

http://www.mathcs.emory.edu/~cheung/Courses/554/Syllabus/5-query-opt/best-left-deep-tree.html

http://www.mathcs.emory.edu/~cheung/Courses/554/Syllabus/5-query-opt/dyn-prog-join3.html

Introduction about left-deep-tree and explanation on why dynamic programming based optimizer works. Read them in project 3.

https://courses.cs.washington.edu/courses/cse444/98au/optimization.ppt

https://dl.acm.org/citation.cfm?doid=275487.275492

http://blog.itpub.net/30206145/viewspace-1651583/ (Chinese version)

Something about how to optimize the Join operator, you can learn cost-based optimization(CBO) and left-deep-tree here. Read them in project 3.

What is more, when implementing the project 4, it is recommended to learn the concepts about transaction management systematically, especially ACID properties, the priority of read/write lock, 2PL protocol, etc.