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Detecting Problems in Database Access Code of Large Scale Systems

Mohamed Nasser, Parminder Flora

Tse-Hsun(Peter) Chen Ahmed E. HassanWeiyi Shang

Existing static analysis tools focus on general anti-patterns in the code

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Coverity PMD Google error-prone

Facebook InferFindBugs

However, these tools do not detect problems related to how developers use frameworks.

Over 67% of Java developers use Object-Relational Mapping (Hibernate) to access databases

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22%67%

There is a huge need for framework-specific tools

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Developers leverage MANY frameworks, but existing tools only support detecting general anti-patterns in the code.

An example class with Java ORM code

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@Entity@Table(name = “user”)public class User{

@Column(name=“id”)private int id;

@Column(name=“name”)String userName;

@OneToMany(fetch=FetchType.EAGER)List<Team> teams;

… other getter and setter methods

User.javaUser class is mapped to “user”

table in DB.

id is mapped to the column “id” in the

user table.

A user can belong to multiple teams.

Eagerly retrieve associated teams when retrieving a

user object.

Accessing the database using ORM

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User u = findUserByID(1);

ORMdatabase

select u from user where u.id = 1;

u.setName(“Peter”);

update user set name=“Peter” where user.id = 1;

Objects SQLs

@Transaction

Developers are often not aware of database access

Wow! I don’t need to worry

about DB code!

ORM code with performance anti-patterns

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Bad systemperformance

We found that performance problems are common in ORM code (MSR

2016).

Implementing DBChecker

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Source code

• Static anti-pattern detection tools.

• DBChecker looks for both functional and performance anti-patterns.

• DBChecker is integrated in industrial practice.

Overview of the presentation

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Anti-patterns Lessons learned when adopting the tool in practice

Overview of the presentation

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Lessons learned when adopting the tool in practice

Anti-patterns

ORM excessive data anti-patternClass User{ @OneToMany (fetch=FetchType.EAGER)

List<Team> teams;}

User u = findUserById(1);u.getName();EOF

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Objects

SQL

Eagerly retrieve teams from DB

User Table Team Table

join Team data is never used!

The performance impact of under-optimal ORM code can be significant (ICSE2014, TSE2016).

Nested transaction anti-pattern

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@Transaction(Propogation.REQUIRED)getUser(){ updateUserGroup(u) …}

Create a DB transaction

@Transaction(Propogation.REQUIRES_NEW)

Conflicting configurations may cause transaction timeout

Misconfigurations can cause both functional and performance problems (ICSE 2016, FSE 2016).

Limitation of current static analysis tools

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Annotations are lost when converting source code to byte code.

Do not consider how developers configure frameworks.

@Transaction(Propogation.REQUIRED)@EAGER

Many problems are related to

framework configurations.

Many configurations are

set through annotations.

Overview of the presentation

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Lessons learned when adopting the tool in practice

Most discussed anti-patterns are related to

incorrect usage of frameworks.

Anti-patterns

Overview of the presentation

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Lessons learned when adopting the tool in practice

Most discussed anti-patterns are related to

incorrect usage of frameworks.

Anti-patterns

Handling a large number of detection results

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• Developers have limited time to fix detected problems.

• Need to help developers prioritize their efforts.

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Prioritizing based on DB tablesUser

Time zone

• Problems related to large or frequently-accessed tables are ranked higher (more likely to be performance bottlenecks).

• Problems related to highly dependable tables are ranked higher.

Developers have different backgrounds

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• Not all developers are familiar with these frameworks and databases.

• Developers may not take the problems seriously if they don’t understand the impact.

Educating developers about the detected problems

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• We hosted several workshops to educate developers about the impact and cause of the problems.

• Walk developers through examples of detected problems.

• May learn new anti-patterns from developers.

Overview of the presentation

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Lessons learned when adopting the tool in practice

Most discussed anti-patterns are related to

incorrect usage of frameworks.

We prioritize problems based on DB tables, and

educate developers about the problems.

Anti-patterns

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Tse-Hsun (Peter) Chen http://petertsehsun.github.io