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Inverted Files, Linked Lists - Database Management - Lecture Slides, Slides of Introduction to Database Management Systems

Inverted Files, DBMS searches, Linked Lists, Circular pointers, Tree Index, Three Alternatives, AKA Pointer Chain are the main points of this lecture.

Typology: Slides

2011/2012

Uploaded on 11/03/2012

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Lecture - 38
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Download Inverted Files, Linked Lists - Database Management - Lecture Slides and more Slides Introduction to Database Management Systems in PDF only on Docsity!

Database

Management

System

Lecture - 38

Inverted Files

The attribute on which we want

direct access, inverted file is created

on that field

File is said to be inverted on that

field

More than one inversions can be

created, even on all attributes

Inverted Files

Inverted file contains the values of

attribute in sorted order and the

relative address of the record

DBMS searches appropriate record

no and hands over to access method

to retrieve the desired record

Linked Lists

AKA Pointer Chain Needs an extra field in the physical record to store the link Relative addresses are used

Linked Lists

Head pointer needs to be stored Pointers for multiple fields can be created Circular pointers Double linked lists

Tree Index

Index is maintained in a hierarchical arrangements of nodes Each node stores key values and pointers; nodes are connected through links

B+ Trees

Number of pointers in a node is

one more than the number of keys

Number of pointers called order of

tree

Distance of all leaf nodes from the

root is same

Example Tree Index

 Index entries :<search key value,

page id> they direct search for

data entries in leaves.

Example where each node can

hold 2 entries.

Example Tree Index 10* 15* 20* 25* 33* 37* 40^ 46^ 51^ 55^ 63* 97*

Root 27*

Example Tree Index 10* 15* 20* 23* 33* 34* 40^ 46^ 51^ 55^ 63* 97*

Root 27*

Insert 22

10* 15* 20* 22* 33* 34* 40^ 46^ 51^ 55^ 63* 97*

Root 27*

Alternatives for Data

Entry k* in Index

What is actually stored in the leaves of the index for key value “k”?

Alternative 1 Actual data record (with key value k )

 If this is used, index structure is a

file organization for data records

(like Heap files or sorted files).

Alternative 1 At most one index on a given collection of data records can use Alternative 1.