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Time to search a sorted database
In computer science using the ordinary binary search to find a certain record in a sorted database, how long will it take? Answer: The binary search will do comparison operation in roughly Log 2 N . It means if the table has N = 1,000,000 record, then to find a certain record it will take 20 comparison operations. How many millisecond each comparison? ( assuming it is 10 millisecond to read a record on a disk ) then 20 x 10 millisecond = 200 ms or 0.2 second to find and display the query record. Log 2 1,000,000 = 19.9 or 20 comparison to find the record. 1,000,000 is also equal to 1e6 when written in exponential notation.
In 1972 B-Tree was invented by Rudolf Bayer and Edward M. McCreight while working at Boeing Research Lab. In computer science, B-Tree is a self balancing tree data structure. Compare to self-balancing binary search trees, the B-Tree is optimized for systems that read and write large blocks of data. B-Trees are a good example of a data structure for external memory. B-Tree data structure is commonly used in databases and filesystems. --source : Wikipedia
Log b N is the optimize way of doing binary search using B-Tree.
Where b is the blocking factor, meaning if you divide your sorted 1,000,000 records by 100 blocks, you can optimize your binary search capability . Log 100 1,000,000 = 3 reads . Then 3 reads x 10 milliseconds = 30 milliseconds.--source : Wikipedia
IBM Cloudant NoSQL document database , MapReduce views are indexes into the dataset with key value pairs and stored in a B-Tree for efficient retrieval by key or range of keys.
Any base Logarithm Log 2 (32) = 5 for example
For base 100 , change 2 to 100
Log
( )
=
Common logarithm is base 10. Base 10 here is shown as a reminder.
Log 10 (1000) is commonly written as Log (1000 ) = 3
Log 10
=
Natural Logarithm (e = 2.718)
Ln e
=
Reviewer: Manual Calculation
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