CH8 - 1. Access Types-- types of access that are supported...

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Basic Concepts 1. An index for a file works like a catalogue in a library. Cards in alphabetic order tell us where to find books by a particular author. 2. In real-world databases, indices like this might be too large to be efficient. We'll look at more sophisticated indexing techniques. 3. There are two kinds of indices. o Ordered indices: indices are based on a sorted ordering of the values. o Hash indices: indices are based on the values being distributed uniformly across a range of buckets. The buckets to which a value is assigned is determined by a function, called a hash function . 4. We will consider several indexing techniques. No one technique is the best. Each technique is best suited for a particular database application. 5. Methods will be evaluated on:
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Unformatted text preview: 1. Access Types-- types of access that are supported efficiently, e.g., value-based search or range search. 2. Access Time-- time to find a particular data item or set of items. 3. Insertion Time-- time taken to insert a new data item (includes time to find the right place to insert). 4. Deletion Time-- time to delete an item (includes time taken to find item, as well as to update the index structure). 5. Space Overhead-- additional space occupied by an index structure. 2. We may have more than one index or hash function for a file. (The library may have card catalogues by author, subject or title.) 3. The attribute or set of attributes used to look up records in a file is called the search key (not to be confused with primary key, etc.)....
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