COMP9315 Final Exam
COMP9315 Final Exam
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The University of Wales
COMP9315 DBMS Implementation
Final Exam
DBMS Implementation
[Instructions] [Notes] [PostgreSQL] [C]
[Q1] [Q2] [Q3] [Q4] [Q5] [Q6] [Q7] [Q8]
Question 4 (6 marks)
Consider a table R(a,b,c,d) indexed by
tuple-based superimposed codeword signatures.
The data and signature files have the following properties:
Page Size 4096 bytes
Number of records (rR) 10000
Record size (RR) 32 bytes
Signature size (m) 58 bits
Bits/attribute (k) 10 bits
False match probability (pF) 1 in 1000
You can make the following (slightly unrealistic) assumptions:
there are no headers on either data pages or signature pages
each page (except the last) is packed with as many tuples as will fit
the table has no primary key attribute
a query like R(?,b,c,d) has exactly 4 genuine matches
this query also has exactly 10 false matches (consistent with pF)
each matching tuple is on a different page
each false match is on a different page
no false match occurs on the same page as a genuine match
Based on the above, answer the following:
How many pages are there in the data file?
How many pages are there in the signature file?
How many pages are read in answering the query R(?,b,c,d)?
(include both signature pages and data pages, as needed)
How many pages are read in answering the query R(?,?,?,?)?
(include both signature pages and data pages, as needed)
What feature of the query signature would allow you to optimise
the page reads for R(?,?,?,?)?
What would be the values of m and k if we decided
to use page-level signatures, rather than tuple-level signatures?
Show all working.
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End of Question
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