how do developers document database usages in source code?boyang/ase15slides.pdf · how do...

How Do Developers Document Database Usages in Source Code?

Mario Linares-Vasquez, Boyang Li, Christopher Vendome, and Denys Poshyvanyk

ASE 2015

Database-centric application (DCA)

DCAs are software systems that rely on databases to persist records using database objects.

Database-centric application (DCA)

DCAs are software systems that rely on databases to persist records using database objects.

Challenges

Challenges

DBManager.getAllInfoByStudentID ()

ID Num PWD Gender Address Year …

… … … … … …

… … … … … …

STUDENT

Challenges

DBManager.getAllInfoByStudentID ()

ID Num PWD Gender Address Year …

… … … … … …

… … … … … …

STUDENT

ID Num PWD …

… … …

… … …

ST_LOGIN

ID Gender Address Year …

… … … … …

… … … … …

ST_DETAILS

Challenges

DBManager.getAllInfoByStudentID ()

ID Num PWD Gender Address Year …

… … … … … …

… … … … … …

STUDENT

ID Num PWD …

… … …

… … …

ST_LOGIN

ID Gender Address Year …

… … … … …

… … … … …

ST_DETAILS

getSTLogin() getSTDetails()

Challenges

UI.student.buttonClickShowAllInfo()

UI.student.quaryAllInfoByID ()

DBManager.getAllInfoByStudentID ()

ID Num PWD Gender Address Year …

… … … … … …

… … … … … …

STUDENT

ID Num PWD …

… … …

… … …

ST_LOGIN

ID Gender Address Year …

… … … … …

… … … … …

ST_DETAILS

getSTLogin() getSTDetails()

Challenges

• How the model is described by a schema • How the database is used in the source code

Related works

Related works

Related works

Related works

No previous work has been done to understand database documentation practices at source code level.

Goal

How Do Developers Document Database Usages in Source Code?

381,161 projects

Methodology

381,161 projects

Identified the projects using SQL 18,828 projects

Methodology

381,161 projects

Identified the projects using SQL 18,828 projects

≥ 1 3,113 projects ≥ 1

Methodology

A survey

A mining-based analysis

3,113 projects

Methodology

A survey

A mining-based analysis

with

147 developers

on

33,045 methods

3,113 projects

Methodology

A survey

A mining-based analysis

with

147 developers

on

33,045 methods

Results

Results

3,113 projects

Methodology

RQ1. Do developers document database-related methods

RQ2. Do developers update comments for database-related methods

RQ3. How difficult is to understand the database schema constraints along call-chains

Research Questions

RQ1. Do developers comment methods in source code that locally execute SQL queries and statements?

SQ1. Do you add/write documentation comments to methods in the source code?

SQ2. Do you write source code comments detailing database schema constraints?

Yes No

122(82.99%)

25(17.01%)

Yes No

32(21.77%)

115(78.23%) Yes No Yes No

32(21.77%)

115(78.23%)

Yes No

32(21.77%)

115(78.23%)

RQ1. Do developers comment methods in source code that locally execute SQL queries and statements?

“The database schema and documentation takes care of that. I can always look at the table definition very easily.”

“Comments related to the database schema and its constraints I consider to be irrelevant to the code using it. The schema, its details, and any quirks about it should be outlined in a separate document.” Yes No

32(21.77%)

115(78.23%)

RQ1. Do developers comment methods in source code that locally execute SQL queries and statements?

23%

7,595 (23%)

In the 3,113 projects, we identified a total of 33,045 methods invoking SQL ueries/statements.

Yes No

32(21.77%)

115(78.23%)

RQ1. Do developers comment methods in source code that locally execute SQL queries and statements?

SQ3. How often do you find outdated comments in source code?

SQ4. When you make changes to database related methods, how often do you update comments?

Never Rarely SometimesFairly Often Always

29(19.73%)

118(80.27%)

RQ2. Do developers update comments of database-related methods during the evolution of a system?

SQ3. How often do you find outdated comments in source code?

SQ4. When you make changes to database related methods, how often do you update comments?

Never Rarely SometimesFairly Often Always

31(21.08%)

116(78.92%)

Never Rarely SometimesFairly Often Always

29(19.73%)

118(80.27%)

RQ2. Do developers update comments of database-related methods during the evolution of a system?

3,113 projects

264 projects

8.5% Had explicit releases

RQ2. Do developers update comments of database-related methods during the evolution of a system?

3,113 projects

264 projects

8.5% Had explicit releases

2,662 methods (Invoke SQL)

RQ2. Do developers update comments of database-related methods during the evolution of a system?

3,113 projects

264 projects

8.5% Had explicit releases

2,662 methods (Invoke SQL)

618 methods

23.2% were updated

RQ2. Do developers update comments of database-related methods during the evolution of a system?

3,113 projects

264 projects

8.5% Had explicit releases

2,662 methods (Invoke SQL)

618 methods

23.2% were updated

512 methods

82.8% didn’t updated comments

RQ2. Do developers update comments of database-related methods during the evolution of a system?

3,113 projects

264 projects

8.5% Had explicit releases

2,662 methods (Invoke SQL)

618 methods

23.2% were updated

512 methods 106 methods

82.8% didn’t updated comments

17.2% updated comments

RQ2. Do developers update comments of database-related methods during the evolution of a system?

106 methods

1 1

3 14

21 4

0 4

2 56

0 10 20 30 40 50 60

（0%,10%]

（10%,20%]

（20%,30%]

（30%,40%]

（40%,50%]

（50%,60%]

（60%,70%]

（70%,80%]

（80%,90%]

（90%,100%]

frequency that the comments were updated when the method was modified

RQ2. Do developers update comments of database-related methods during the evolution of a system?

106 methods

1 1

3 14

21 4

0 4

2 56

0 10 20 30 40 50 60

（0%,10%]

（10%,20%]

（20%,30%]

（30%,40%]

（40%,50%]

（50%,60%]

（60%,70%]

（70%,80%]

（80%,90%]

（90%,100%]

frequency that the comments were updated when the method was modified

40(37.73%)

RQ2. Do developers update comments of database-related methods during the evolution of a system?

SQ5. How difficult is it to trace the schema constraints (e.g., foreign key violations) from the methods with SQL statements to top-level method callers

Very Easy Easy ModerateHard Very Hard

50(34.01%)

97(65.99%)

RQ3. How difficult is it for developers to understand propagated schema constraints along call-chains?

Lessons learnt

(i) Documenting database usages and constraints is not a common practice in source code methods

(ii) Developers do not update comments when changes are done to database-related methods

(iii) Tracing schema constraints through call-chains in the call graph is not an easy task in most of the cases

Lessons learnt

(i) Documenting database usages and constraints is not a common practice in source code methods

(ii) Developers do not update comments when changes are done to database-related methods

(iii) Tracing schema constraints through call-chains in the call graph is not an easy task in most of the cases

Documentation

Automation

Calling context

Summary

Summary

Summary

Summary