B+Trees - 1 B+ Tree: Most Widely Used Index Insert/delete...

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Unformatted text preview: 1 B+ Tree: Most Widely Used Index Insert/delete at log F N cost; keep tree height-balanced . (F = fanout, N = # leaf pages) Minimum 50% occupancy (except for root). Each node contains d <= m <= 2 d entries. The parameter d is called the order of the tree. Supports equality and range-searches efficiently. Index Entries Data Entries ("Sequence set") (Direct search) 2 Example B+ Tree Search begins at root, and key comparisons direct it to a leaf. Search for 5*, 15*, all data entries >= 24* ... Based on the search for 15*, we know it is not in the tree! Root 17 24 30 2* 3* 5* 7* 14* 16* 19* 20* 22* 24* 27* 29* 33* 34* 38* 39* 13 3 B+ Trees in Practice Typical order: 100. Typical fill-factor: 67%. average fanout = 133 Typical capacities: Height 4: 133 4 = 312,900,700 records Height 3: 133 3 = 2,352,637 records Can often hold top levels in buffer pool: Level 1 = 1 page = 8 Kbytes Level 2 = 133 pages = 1 Mbyte Level 3 = 17,689 pages = 133 MBytes 4 Inserting a Data Entry into a B+ Tree Find correct leaf L. Put data entry onto L ....
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This note was uploaded on 02/13/2011 for the course 332 351 taught by Professor Staff during the Fall '08 term at Rutgers.

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B+Trees - 1 B+ Tree: Most Widely Used Index Insert/delete...

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