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14 lines
893 B
TeX
14 lines
893 B
TeX
\subsubsection{Access methods}
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\inlinedefinition[Access Methods] typically refers to the operations and data structures used for reading data from the buffer cache into the private space of the worker thread
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The basic access method is \bi{sequential scan}, where all pages of the table are read from beginning to end.
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Indexing is used to avoid having to scan the whole table.
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There are many indexing techniques, but we will focus on three indexing techniques in this section, hashing, B+ trees and bitmaps.
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Hashing is primarily used to randomize access to the data, finding data based on a key (hash and access concept)
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and both as an index for tables and used to implement operators.
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B+ trees on the other hand are used to order data along the values of one attribute, but require traversal, unless we are looking for consecutive values.
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They are thus only used as an indexing mechanism.
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