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Chapter 14: Indexing Structures for Files
CHAPTER 14: INDEXING STRUCTURES FOR FILES
Answers to Selected Exercises
14.14 Consider a disk with block size B=512 bytes. A block pointer is P=6 bytes long,
and a record pointer is P R =7 bytes long. A file has r=30,000 EMPLOYEE records
of fixedlength. Each record has the following fields: NAME (30 bytes), SSN (9
bytes), DEPARTMENTCODE (9 bytes), ADDRESS (40 bytes), PHONE (9 bytes),
BIRTHDATE (8 bytes), SEX (1 byte), JOBCODE (4 bytes), SALARY (4 bytes, real
number). An additional byte is used as a deletion marker.
Answers:
(a) Calculate the record size R in bytes.
(b) Calculate the blocking factor bfr and the number of file blocks b assuming an
unspanned organization.
(c) Suppose the file is ordered by the key field SSN and we want to construct a primary
index on SSN. Calculate (i) the index blocking factor bfr i (which is also the index
fanout fo); (ii) the number of firstlevel index entries and the number of firstlevel
index blocks; (iii) the number of levels needed if we make it into a multilevel
index; (iv) the total number of blocks required by the multilevel index; and
(v) the number of block accesses needed to search for and retrieve a record from
the filegiven its SSN valueusing the primary index.
(d) Suppose the file is not ordered by the key field SSN and we want to construct a
secondary index on SSN. Repeat the previous exercise (part c) for the secondary
index and compare with the primary index.
(e) Suppose the file is not ordered by the nonkey field DEPARTMENTCODE and we want
to construct a secondary index on SSN using Option 3 of Section 5.1.3, with an extra
level of indirection that stores record pointers. Assume there are 1000 distinct
values of DEPARTMENTCODE, and that the EMPLOYEE records are evenly distributed
among these values. Calculate (i) the index blocking factor bfr i (which is also the
index fanout fo); (ii) the number of blocks needed by the level of indirection that
stores record pointers; (iii) the number of firstlevel index entries and the
number of firstlevel index blocks; (iv) the number of levels needed if we make it a
multilevel index; (v) the total number of blocks required by the multilevel index
and the blocks used in the extra level of indirection; and (vi) the approximate
number of block accesses needed to search for and retrieve all records in the file
having a specific DEPARTMENTCODE value using the index.
(f) Suppose the file is ordered by the nonkey field DEPARTMENTCODE and we want to
construct a clustering index on DEPARTMENTCODE that uses block anchors (every
new value of DEPARTMENTCODE starts at the beginning of a new block). Assume
there are 1000 distinct values of DEPARTMENTCODE, and that the EMPLOYEE
records are evenly distributed among these values. Calculate (i) the index blocking
factor bfr i (which is also the index fanout fo); (ii) the number of firstlevel
index entries and the number of firstlevel index blocks; (iii) the number of levels
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 Fall '09
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