1. Instructors: Winston Hsu, Hao-Hua Chu Fall 2009
HW4: Buffer Manager
Instructors: Winston Hsu, Hao-Hua Chu
Fall 2009

2. Architecture of a DBMS Query Query Optimization and Execution
Relation Operators
File and Access Methods
Buffer Management
Disk Space Management DB

3. Buffer Manager Simple Buffer Manager Structure Operations
Pages in the buffer pool is not ordered in any way
Hash table to figure out what frame a given disk page occupies
Love/Hate buffer replace algorithm
Operations
bring a disk page into the buffer pool and pin it
unpin a page in the buffer pool
allocate/de-allocate pages on disk
flush/flush all buffer page(s) into the disk page

4. Buffer Manager Memory Structure
Buffer Page Description
FrameDesc
pageNo dirtyFlag pin_count
numbuf
Buffer Pool
Page
Buffer Hash Table
pageNo
frameNo
*next ……
HTSIZE ……

5. Love/Hate Replacement
upper level user hints the buffer manager that the page is loved or hated.
Replace hated pages first, then loved pages.
MRU list for the hated pages, LRU list for the loved pages
“ Love conquers hate “

6. Functions (in buf.h and buf.C)
BufMgr
Initializes buffer manager: create buffer pool, buffer pool description, hash table….etc.
Malloc, calloc…..
pinPage, unpinPage, newPage, freePage, flushPage, flushAllPages
Use Minibase API
Your own functions (if needed)
For hash table and replacement policy

7. Minibase APIs Page Errors handling
Status MINIBASE_DB->read_page(PageId pageno, Page* pageptr)
Status MINIBASE_DB->write_page(PageId pageno, Page* pageptr)
Status MINIBASE_DB->allocate_page(PageId& start_page_num, int run_size=1)
Status MINIBASE_DB->deallocate_page(PageId start_page_num, int run_size=1)
Errors handling
status = MINIBASE_DB->write_page(pageid, &bufPool[i]);
if (status != OK) { // status: OK or FAIL
// your own error message }

8. Get Started Read the PDF for detail description.
Group assignment (at most 2 people/group)
Download BufMgr for source code.
Read README.first before you strat.
Post your questions on ptt.cc / CSIE_DBMS.
Minibase homepage and Google