January 2012
Intermediate to advanced
296 pages
5h 4m
English
Content preview from Joe Celko's Trees and Hierarchies in SQL for Smarties, 2nd EditionBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Chapter 5. Frequent Insertion Trees
The problem in a nested sets tree with frequent insertions is that the (lft, rgt) pairs have to be adjusted so often that locking the table, changing the rows, and unlocking the table again become a major overhead. The nested sets model does not require that the union of rgt and lft numbers be an unbroken sequence to show nesting. All you need is the condition that (lft < rgt), uniqueness of lft and rgt numbers, and that subordination is represented by containment of one (lft, rgt) pair within the ranges of the other (lft, rgt) pairs.
Keywords: floating point numbers, spread, data type, reorganization, rational numbers, nested intervals model, depth-first convergence point, breadth-first convergence point, depth-first ...
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