Assignment 4 “Database Management System”

NWEN 241 Assignment 4
“Database Management System”

In the previous assignment, you implemented a database table using a dynamically allocated array (of structures) for holding records in memory. In
this assignment, you will use vector and linked list to implement the same
database table. You will also use File input/output operations to retrieve
the table from a comma-separated value (CSV) file.
Sample code showing an example on how you can test your code are
provided under the files directory in the archive that contains this file.
Full marks is 100.
Instructions and Submission Guidelines:
• You should provide appropriate comments to make your source code
readable. If your code does not work and there are no comments,
you may lose all the marks. See the marking criteria at the end of this
document for details about the marks for commenting.
• You should follow a consistent coding style when writing your source
code. See the marking criteria at the end of this document for details
about the marks for coding style.
• Submit the required files to the Assessment System (https://apps.
ecs.vuw.ac.nz/submit/NWEN241/Programming_Assignment_
4) on or before the submission deadline.
• Late submissions (up to 48 hours from the submission deadline) will
be accepted but will be penalized. No submissions will be accepted
48 hours after the submission deadline.
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NWEN 241 2019-T1 “Database Management System” Assignment 4
Program Design
(This is already partly discussed in Assignment #3.)
A fundamental concept in DBMS is the table. A table consists of zero or
more records or entries, and each record can have one or more fields or
columns. An example of a table for storing information about movies is
shown below:
id title year director
13 The Shawshank Redemption 1994 Frank Darabont
25 The Godfather 1972 Francis Ford Coppola
31 The Dark Knight 2008 Christopher Nolan
40 The Godfather: Part II 1974 Francis Ford Coppola
55 The Lord of the Rings: The Return of the King 2003 Peter Jackson
72 Pulp Fiction 1994 Quentin Tarantino
This table contains 6 rows or records. Each record has 4 fields, namely, id,
title, year, and director.
In this assignment, you will focus on implementing a single database
table with 4 fields (id, title, year, and director). A C structure with tag
movie will be used for holding a table record. The structure declaration is
given below and is defined within dbms2 namespace in dbms2.hh:
namespace dbms2 {
struct movie {
unsigned long id;
char title[50];
unsigned short year;
char director[50];
};
}
Task 1.
Basics [30 Marks]
In this task, you will declare a C++ abstract class for representing a database
table. The class should be named AbstractDbTable and should have the
following public members:
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NWEN 241 2019-T1 “Database Management System” Assignment 4
• A function named rows() which returns an integer, and should not
modify any member variables. This should be declared as a pure
virtual function. In the implementation, the function should return the
number of rows in the table.
• A function named show() which accepts an integer parameter, and
should not modify any member variables. This should be declared as
a pure virtual function. In the implementation, the function should display the information stored in a row. You are free to format the print
out, but all fields of the row should be shown. The input parameter
indicates the row number of the record to be displayed. If the record
exists, the function should return true, otherwise, it should return
false.
• A function named add() which accepts a reference to a movie structure. This should be declared as a pure virtual function. In the implementation, the function should insert a record into the table. The input
parameter contains the record details to be stored in the table. The
function should return true if the record was successfully inserted
into the table, otherwise, it should return false.
• A function named remove() which accepts an unsigned long integer. This should be declared as a pure virtual function. In the implementation, the function should remove a record from the table. The input parameter contains the id of the record to be removed. The function should return true if the removal was successful, otherwise, it
should return false.
• A function named get() which accepts an integer parameter and
should not modify any member variables. This should be declared
as a pure virtual function. In the implementation, the function should
return a pointer to a movie structure. The input parameter indicates
the row number of the record to be returned.
• bool loadCSV(const char *infn): This should be declared as
a normal (non-virtual) function. See Task 5 for more details.
• bool saveCSV(const char *outfn): This should be declared
as a normal (non-virtual) function. See Task 6 for more details.
Note that you have implemented the first four functions in Assignment #3
for a database table implemented as an array of structures. In this assign3
NWEN 241 2019-T1 “Database Management System” Assignment 4
ment, you will implement them for a database table that uses a vector (Task
4) and a linked list (Task 7).
The class should be defined within dbms2 namespace.
Save the class in a header file named dbms2.hh.
Task 2.
Basics [10 Marks]
Declare a C++ class named VectorDbTable that is a subclass of AbstractDbTable.
You will use this class to implement a database table using a vector. You
may declare constructors, destructors, additional member variables and
functions. Provide sufficient comments to justify the declaration of these
additional members.
The class should be defined within dbms2 namespace.
Save the class in a header file named vdb.hh.
Task 3.
Basics [10 Marks]
Declare a C++ class named LinkedListDbTable that is a subclass of
AbstractDbTable. You will use this class to implement a database table using a linked list data structure. You may declare constructors, destructors, additional member variables and functions. Provide sufficient
comments to justify the declaration of these additional members.
The class should be defined within dbms2 namespace.
Save the class in a header file named lldb.hh.
Task 4.
Completion [10 Marks]
Provide an implementation of the class VectorDbTable as declared in
vdb.hh.
Save the implementation in vdb.cc.
(Hint: Implementing a class means implementing all unimplemented member functions, constructors and destructors declared in the class declaration.)
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NWEN 241 2019-T1 “Database Management System” Assignment 4
Task 5.
Completion [10 Marks]
Provide an implementation of the member function
bool loadCSV(const char *infn)
in the AbstractDbTable class. The input parameter infn denotes the
file name of a comma-separated value (CSV) file to be loaded. In a valid
CSV file, a line represents a record. An example of a line in a valid CSV file
is shown below:
13,The Shawshank Redemption,1994,Frank Darabont
which has 4 fields (id, title, year, and director) separated by commas. For
simplicity, assume that the 2nd (title) and 4th (director) fields would not
contain commas.
This function should perform the following:
• Open the file infn for reading. You may use either C or C++ File
I/O.
• Read in all lines from infn. Add every line (which corresponds to
a record) from the file into the table. When a line not following the
expected format is encountered, the reading of the rest of the lines is
terminated.
• Close the file.
The function should return false if:
• The file infn does not exist or cannot be opened for reading.
• The file infn is not a valid CSV file (at least one of the lines does not
follow the expected format.)
Otherwise, it should return true.
Save the implementation in dbms2.cc.
(Hint: You can use the add() member function to add a line of record.)
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NWEN 241 2019-T1 “Database Management System” Assignment 4
Task 6.
Completion [10 Marks]
Provide an implementation of the member function
bool saveCSV(const char *outfn)
in the AbstractDbTable class. The input parameter outfn denotes the
file name to write to.
This function should perform the following:
• Open the file outfn for writing. The file must be emptied. You may
use either C or C++ File I/O.
• Write every record from the table into the file. A record must be written as a comma-separated value (see Task 5 for the specifications of a
line of record.)
• Close the file.
The function should return false if:
• The file outfn cannot be opened for writing.
• Errors were encountered while writing to the file.
Otherwise, it should return true.
Save the implementation in dbms2.cc.
(Hint: You can use the get() member function to get a line of record.)
Task 7.
Challenge [10 Marks]
Provide an implementation of LinkedListDbTable as declared in lldb.hh.
Your implementation should not use the C++ standard template library.
This means that you should implement the link list data structure in your
code (which involves the use of C structure, pointers, and dynamic memory allocation).
Save the implementation in lldb.cc.
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NWEN 241 2019-T1 “Database Management System” Assignment 4
(Hint: Implementing a class means implementing all unimplemented member functions, constructors and destructors declared in the class declaration.)
Task 8.
Challenge [10 Marks]
Write a main() function that accepts command line arguments. Save the
implementation in dbcmd.cc.
The program should perform the following:
1. Create an instance of a database table. You may use either VectorDbTable
or LinkedListDbTable.
2. Load a CSV database table file named default.csv (provided).
3. If the first command line argument is showall, it will display all
rows in the table.
4. If the first command line argument is show, then it must be followed
by a second command line argument. The second argument is the
row number of the record to be displayed.
5. Destroy instance of database table.
If there are more command line arguments than required, the excess arguments are simply ignored.
To illustrate, suppose that the program is compiled as dbcmd. Suppose
further that the file default.csv contains the following lines:
13,The Shawshank Redemption,1994,Frank Darabont
25,The Godfather,1972,Francis Ford Coppola
31,The Dark Knight,2008,Christopher Nolan
Then if we execute
dbcmd showall
The output should be something like (depending on how you implemented
the show() member function)
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NWEN 241 2019-T1 “Database Management System” Assignment 4
13 The Shawshank Redemption 1994 Frank Darabont
25 The Godfather 1972 Francis Ford Coppola
31 The Dark Knight 2008 Christopher Nolan
If we execute
dbcmd showall 100
The third argument 100 is simply ignored. Hence, the output should be the
same as above.
If we execute
dbcmd show 0
The output should be something like
13 The Shawshank Redemption 1994 Frank Darabont
which is the first row of the table. Note that row index starts from 0.
If we execute
dbcmd show 100
The output should be something like
Error: Row 100 does not exist.
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NWEN 241 2019-T1 “Database Management System” Assignment 4
Marking Criteria for Tasks 1 – 3:
Criteria Weight Expectations for Full Marks
Commenting 10% Source code contains sufficient and appropriate
comments
Coding Style 10% Source code is formatted, readable and uses a
coding style consistently
Correctness 40% Addresses all specifications and correctly uses
syntax in the declarations and/or definitions
Completeness 40% Declaration and/or definition of all required
members
100%
Marking Criteria for Tasks 4–8:
Criteria Weight Expectations for Full Marks
“Compilability” 10% Source code compiles without warnings
Commenting 10% Source code contains sufficient and appropriate
comments
Coding Style 10% Source code is formatted, readable and uses a
coding style consistently
Correctness 70% Implements all specifications correctly and
handles all possible cases correctly
100%
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