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代做CSI 410留学生程序、代写Database Systems程序

来源:珠穆朗玛网 发布时间:2020-02-18

代做CSI 410留学生作业、代写Database Systems作业、代做Java程序语言作业
CSI 410. Database Systems – Spring 2020
Programming Assignment I
The total grade for this assignment is 100 points. The deadline for this assignment is 11:59
PM, February 20, 2020. Submissions after this deadline will not be accepted. Students are
required to enter the UAlbany Blackboard system and then upload a .zip file (in the form of [first
name] [last name].zip) that contains the Eclipse project directory and a short document describing:
• any missing or incomplete elements of the code
• any changes made to the original API
• the amount of time spent for this assignment
• suggestions or comments if any
In this programming assignment, you need to implement a storage manager that maintains a
series of data objects in each data file. You first need to install and run Eclipse on your machine
and import the “storage manager” project (see Appendix A). Please generate an API document
(see Appendix B) and then take a look at that document as well as the source code to familiarize
yourself with this assignment. This assignment provides you with a set of incomplete classes (in
particular, see SlottedPage, FileManager, and BufferedFileManager which contain methods
currently throwing an UnsupportedOperationException). You will need to write code for these
classes. Your code will be graded by running a set of unit tests and then examining your code (see
SlottedPageTest and FileManagerTest which use JUnit1
, as well as BufferedFileManagerTest
which produces output messages). For details of running these tests, refer to Appendix A. Note
that passing unit tests does NOT necessarily guarantee that your implementation is correct and
efficient. Please make sure that your code is correct and efficient so that it will not cause any
problem in many other cases not covered by the unit tests. If you have questions, please contact
the TA(s) or the instructor. The remainder of this document describes the components that you
need to implement.
Part 1. The Slotted Page Structure (50 points)
The slotted page structure allows a storage manager to store variable-length records (data
objects) within a fixed size page (an in-memory copy of a disk block). Each page is essentially a
byte array that stores a header (at the beginning) and a number of data objects (at the end). The
header of a page consists of (1) a 4-byte integer representing the number of entries in the page for
storing data objects, and (2) a series of 4-byte integers (one for each data object) each of which
represents where the corresponding data object is stored within the page (i.e., the location of the
corresponding data object within the page). Each page has, between its header and data objects,
a free space where more data objects and header entries can be added. For further details of the
slotted page structure, refer to Section 13.2.2 of the textbook. Upon a request to delete a data
object from a page, the corresponding header entry (for storing the location of the data object)
is simply set to -1 to indicate that there is no associated data object (the actual object is NOT
necessarily removed from the page).
1
http://junit.org
1
In this part, you need to implement the following methods (your code needs to pass all of the
5 tests in SlottedPageTest):
• add(Object o): adds the specified object o in the SlottedPage on which this method is
invoked. This method must first save the object o in the free space of the SlottedPage by
calling the save(Object o) method. This save(Object o) method returns an int value
indicating the location at which the object o is saved in the SlottedPage. That int value
must be stored at the right header entry of the SlottedPage so that the saved object o can
be accessed in the future. For example, assume that object “123” is saved at location 2038 in
the byte array of an empty SlottedPage. Then, the first 4 bytes of the byte array (i.e., the
beginning of the header) must store an int value 1 to indicate that there is only one entry in
the header (in response to the addition of object “123”). The next 4 bytes of the byte array
(i.e., the 0th entry in the header) must store 2038 (i.e., the location at which “123” is saved).
When an additional object “456” is saved at location 2028 in the byte array, the first 4 bytes
of the header must store 2 (to indicate that there are two entries in the header) and the 1st
entry (i.e., the entry after the 0th entry) in the header must store 2028 (i.e., the location at
which “456” is saved). To find the number of entries that the SlottedPage currently has, use
the entryCount() method. To set the number of entries in the header to an int value, use
the setEntryCount(int count) method. To save location l at the ith entry in the header,
call saveLocation(i, l).
• get(int index): returns the object at the specified index in the SlottedPage on which this
method is invoked. For example, get(0) returns the object at index 0 (i.e., the object whose
location is stored at the 0th entry in the header) and get(1) returns the object at index
1. This method must first find the location of the object at the specified index by calling
the getLocation(int index) method. This getLocation(int index) method returns the
int value stored at the header entry specified by index (i.e., the index-th header entry).
If that location is -1, meaning that the object was removed from the SlottedPage, the
get(int index) method needs to return null. Otherwise, get(int index) needs to obtain
the object by calling the toObject(byte[] b, int offset) method (with offset set to
the return value of getLocation(int index)) and then return that obtained object. If the
given index cannot match any of the entries in the SlottedPage (e.g., get(-1)), the method
needs to throw an IndexOutOfBoundsException.
• remove(int index): removes the object at the specified index from the SlottedPage on
which this method is invoked. This method must save -1 at the appropriate entry in the
header. This method must also return the object removed (i.e., the object previously stored
at the specified index).
• iterator(): returns an iterator over the objects (excluding those removed) stored in the
SlottedPage on which this method is invoked. To find the number of entries in the current
SlottedPage, use entryCount(). To get the object at each index, call get(int index).
Note that get(int index) returns null if there is currently no object at the specified index
due to the deletion of the previous object. Feel free to add an auxiliary class or data structure
for this iterator() method.
• compact(): reorganizes the SlottedPage on which the method is invoked (in order to maximize
the free space of that SlottedPage). This method is used by the save(Object o)
method when the object to save cannot fit into the current free space of the SlottedPage.
This method needs to move objects at the end of the SlottedPage in a manner that eliminates
the space previously wasted by the objects removed from the SlottedPage.
2
Please make sure that your code passes all of the tests in SlottedPageTest.
Part 2. The Basic Storage Manager Implementation (40 points)
In this part, you need to implement, in FileManager.java, a basic storage manager that maintains
a series of data objects in each data file without buffering (i.e., reading/writing SlottedPages
directly from/to data files). The methods to complete are as follows (your code needs to pass all
of the 4 tests in FileManagerTest):
• put(int fileID, Long location, Object o): puts object o at location location in the
file specified by fileID. Here, location has a long-type value, whose first half (4 bytes
corresponding to an integer) represents the ID of the page (e.g., page 0, page 1, etc.) and the
second half represents the index within the page. For example, put(10, 0x00000001L, o)
stores object o in page 0 of the file specified by ID 10 (i.e., the first disk block in the file) at
index 1 within the page. On the other hand, put(10, 0x00010000L, o) stores object o in
page 1 of the file specified by ID 10 (i.e., the second disk block in the file) at index 0 within
the page. Given a long-type argument location, use first(location) to get the ID of the
page and second(location) to get the index within the page. After finding an appropriate
page p, call put(int index, Object o) on p to put the object in that page and then call
the updated(p, fileID) method of FileManager to indicate that the page p is updated
(then the updated(p, fileID) method of FileManager automatically writes the page to
the appropriate data file). If the location argument has an inappropriate value (e.g., its first
half refers to page -1), then put(int fileID, Long location, Object o) needs to throw
an InvalidLocationException.
• get(int fileID, Long location): returns the object at location location in the file specified
by fileID.
• remove(int fileID, Long location): removes the object at location location from the
file specified by fileID.
• iterator(int fileID): returns an iterator over all objects stored in the the file specified
by fileID. This method needs to use page(int fileID, int pageID) of FileManager and
iterator() of SlottedPage. Make sure this method efficiently uses the memory (e.g., does
NOT put all of the objects in the memory first thereby incurring high space overhead and
then return an iterator over these objects).
Please verify your code using the tests in FileManagerTest.
3
Part 3. Buffer Management (10 points)
The FileManager class implemented in Part 2 directly accesses data files (i.e., no buffering),
causing disk seeks frequently. In this part, you need to implement the BufferedFileManager class
so that it extends the functionalities of FileManager in a manner that benefits from buffering
(i.e., frequently used pages are kept in memory, thereby enabling fast read and write operations).
Furthermore, you need to implement a page eviction policy for the cases where there are too many
pages to keep in the main memory. The choice of eviction policy is up to you. It is not necessary
to do something sophisticated. Describe your policy in the document that you submit.
When BufferedFileManager is implemented correctly, BufferedFileManagerTest will produce
some output as follows (the exact number of reads and writes may vary depending on the
buffering strategy; however, there should in general be less reads and writes as the buffer size
increases):
buffer size : 4 pages
1000 additions % [ { name : table0 . dat , reads : 0 , writes : 3 8 } ]
10 removals % [ { name : table0 . dat , reads : 1 0 , writes : 4 8 } ]
iteration over 990 elements % [ { name : table0 . dat , reads : 5 2 , writes : 5 2 } ]
shut down % [ { name : table0 . dat , reads : 5 2 , writes : 5 2 } ]
buffer size : 16 pages
1000 additions % [ { name : table0 . dat , reads : 0 , writes : 2 6 } ]
10 removals % [ { name : table0 . dat , reads : 9 , writes : 3 5 } ]
iteration over 990 elements % [ { name : table0 . dat , reads : 4 8 , writes : 5 1 } ]
shut down % [ { name : table0 . dat , reads : 4 8 , writes : 5 1 } ]
buffer size : 64 pages
1000 additions % [ { name : table0 . dat , reads : 0 , writes : 0 } ]
10 removals % [ { name : table0 . dat , reads : 0 , writes : 0 } ]
iteration over 990 elements % [ { name : table0 . dat , reads : 0 , writes : 0 } ]
shut down % [ { name : table0 . dat , reads : 0 , writes : 4 2 } ]
Appendix A. Installing Eclipse and Importing a Java Project
1. Visit:
http://www.eclipse.org/downloads/
2. From the web site, download the eclipse installer (those for Linux, Windows, and Mac OS X
are available) and then choose “Eclipse IDE for Java Developers” and install it.
3. After finishing installation, start Eclipse.
4. When Eclipse runs for the first time, it asks the user to choose the workspace location. You
may use the default location.
5. In the menu bar, choose “File” and then “Import”. Next, select “General” and “Existing
Projects into Workspace”. Then, click the “Browse” button and select the “storage manager.zip”
file contained in this assignment package.
6. Once the project is imported, you can choose one among SlottedPageTest.java, FileManagerTest.java,
and BufferedFileManagerTest.java in the storage.test package and then run it by clicking
the icon highlighted in Figure 1.
4
Figure 1: Eclipse
Appendix B. Creating API documents using javadoc
One nice feature of Java is its support for “documentation comments”, or “javadoc” comments,
which you can use to automatically produce documentation for your code. Javadoc comments start
with “/**”. Inside a javadoc comment, there are some special symbols, like @param and @return.
You can create HTML-based API documents from the source as follows:
1. Click the “storage manager” project icon in the Navigator or Project Explorer window.
2. Select “Generate Javadoc” from the “Project” menu.
3. In the “Generate Javadoc” dialog box, press the “Finish” button.
As it runs, it tells you that it’s generating various things. When it is finished, a few new folders
should appear in your project: doc, doc.javadoc, and doc.resources. See what got generated (to
open the newly created HTML documentation files in a web browser window, just double-click
them; you can start with “index.html”).

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