HW6: Sort-Merge Join
Instructors: Winston Hsu, Hao-Hua Chu
Fall 2009
Architecture of a DBMS
Query
Query Optimization and Execution
Relation Operators(Join)
File and Access Methods
Buffer Management
Disk Space Management
DB
Sort-Merge Join
Example
sid
sname
sid
sname
sname
BID
sname
BID
31
A
31
A
A
112
C
118
28
E
22
A
A
168
B
112
22
A
36
C
B
112
A
112
36
C
44
D
B
101
A
168
44
D
28
E
C
118
B
101
Sort by sname
Get the first tuples
Merge
sid
sname
BID
31
A
112
31
A
168
22
A
112
22
A
168
36
C
118
Some APIs
• Sort constructor(… outfile …)
– Outfile : Name of sorted heapfile should be distinct
• HeapFile constructor
• HeapFile->openScan()
– Followed by scan->getNext() and get the firstRecord
• tupleCmp() : compare tuples
• Scan->position()
– Position the scan cursor to the record with the given rid.
Other
• Output format:
if
recA
=
recA
,then write
recA
recA
• If there are any questions, you can post them
on ptt.cc / CSIE_DBMS.
• Deadline: 23:59 Jan 6 (Wednesday), 2010
Heapfile
“Database Management Systems, Third Edition” by Ramakrishnan and Gehrke