B+ Tree Index
B+ tree indices are considered as an alternative to indexed-sequential files. Disadvantages of indexed-sequential files are performance degrades as file grows since many overflow blocks get created and periodic reorganization of entire file is required. Advantages of B+ tree index files: Automatically reorganizes itself with small, local and changes in the face of insertions and deletions. Reorganization of entire file is not required to maintain performance. Disadvantages of B+ trees is extra insertion and deletion overhead, space overhead. Advantages of B+ trees outweigh disadvantages as B+ trees are used extensively. A B+ tree is a rooted tree satisfying the following properties: All paths from the root to leaf are of the same length. Each node which is not a root or a leaf has between (n / 2) and n children. A leaf node has between the values ((n - 1)/2) and (n-1). Special cases: If the root is not a leaf it has at least 2 children. If the root is a leaf that is, there are no other nodes in the tree then it can have between 0 and (n-1) values.
Summary
B+ tree indices are considered as an alternative to indexed-sequential files. Disadvantages of indexed-sequential files are performance degrades as file grows since many overflow blocks get created and periodic reorganization of entire file is required. Advantages of B+ tree index files: Automatically reorganizes itself with small, local and changes in the face of insertions and deletions. Reorganization of entire file is not required to maintain performance. Disadvantages of B+ trees is extra insertion and deletion overhead, space overhead. Advantages of B+ trees outweigh disadvantages as B+ trees are used extensively. A B+ tree is a rooted tree satisfying the following properties: All paths from the root to leaf are of the same length. Each node which is not a root or a leaf has between (n / 2) and n children. A leaf node has between the values ((n - 1)/2) and (n-1). Special cases: If the root is not a leaf it has at least 2 children. If the root is a leaf that is, there are no other nodes in the tree then it can have between 0 and (n-1) values.
Things to Remember
- B+ tree indices are considered as an alternative to indexed-sequential files. Disadvantages of indexed-sequential files are:
Performance degrades as file grows since many overflow blocks get created.
Periodic reorganization of entire file is required. - Advantages of B+ tree index files:
Automatically reorganizes itself with small, local and changes in the face of insertions and deletions.
Reorganization of entire file is not required to maintain performance. - Disadvantages of B+ trees is Extra insertion and deletion overhead, space overhead.
- Advantages of B+ trees outweigh disadvantages as B+ trees are used extensively.
MCQs
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Subjective Questions
Q1:
Define tooth decay.
Type: Short Difficulty: Easy
Q2:
Explain about dental caries.
Type: Long Difficulty: Easy
<p><strong>Dental Caries (Tooth Decay)</strong></p>
<p>It is an erosive process that can causes destruction of outer enamel of the tooth. The most common causes of tooth loss are dental decay. Plaque is the major cause of dental caries.</p>
<p> </p>
<p><strong><u>Pathophysiology</u></strong></p>
<p>Bacteria</p>
<p>The primary bacteria involved in the pathogenesis of caries is Streptococcus mutans, but many other bacteria have also been implicated, including S sobrinus, Actinomycessp, and Lactobacillus sp.</p>
<p> </p>
<p>High levels of cariogenic bacteria are indicative of active caries process and are associated with increased risk of new caries development</p>
<p>Plaque is composed of salivary proteins that adhere to teeth, as well as bacteria and their byproducts.</p>
<p>Plaque harbors the bacteria that initiate the demineralization process.</p>
<p>Adequate plaque control can reduce the likelihood of developing dental caries.</p>
<p><strong><u>Etiology</u></strong></p>
<p>Dental plaque</p>
<p>Diet</p>
<p><strong><u>Clinical manifestations</u></strong></p>
<p>Pain, sensitivity to cold and hot.</p>
<p><strong><u>Diagnostic investigation</u></strong></p>
<p>Examination of tooth</p>
<p>X-ray study</p>
<p> </p>
<p><strong><u>Management</u></strong></p>
<p>Prevention</p>
<p>Injection of fluoridated water</p>
<p>Application of topical fluoride</p>
<p>Regular dental check up</p>
<p>Encourage performing regular brushing and rinsing.</p>
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B+ Tree Index
B+ Tree Index:
B+ tree indices are considered as an alternative to indexed-sequential files. Disadvantages of indexed-sequential files are:
- Performance degrades as the file grows since many overflow blocks get created.
- Periodic reorganization of the entire file is required.
Advantages of B+ tree index files:
- Automatically reorganizes itself with small, local and changes in the face of insertions and deletions.
- Reorganization of the entire file is not required to maintain performance.
Disadvantages of B+ trees:
- Extra insertion and deletion overhead, space overhead.
Advantages of B+ trees outweigh disadvantages
- B+ trees are used extensively.
A B+ tree is a rooted tree satisfying the following properties:
- All paths from the root to leaf are of the same length.
- Each node which is not a root or a leaf has between (n / 2) and n children.
- A leaf node has the values ((n - 1)/2) and (n-1).
- Special cases:
If the root is not a leaf it has at least 2 children.
If the root is a leaf that is, there are no other nodes in the tree then it can have between 0 and (n-1) values.
Typical node:
- Ki is the search-key values.
- Pi is the pointers to children (for non-leaf nodes) or pointers to records or buckets of records for leaf nodes.
- The search-keys in a node are ordered in the form:
K1 < K2 < K3 < .... < Kn-1.
References:
- H.F.Korth and A. Silberschatz,"Database system concepts",McGraw Hill,2010
- A.K.Majumdar and p, Bhatt acharya,"Database Management Systems",Tata McGraw Hill,India,2004
- F.Korth, Henry. Database System Concepts. 6th edition.
Lesson
File Structure and Hashing
Subject
Computer Engineering
Grade
Engineering
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