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This implementation is a hybrid between the basic bitmap index (without compression) and the list of Row Identifiers (RID-list). Overall, the index is organized as a B+tree. When the column cardinality is low, each leaf node of the B-tree would contain long list of RIDs. In this case, it requires less space to represent the RID-lists as bitmaps.
B-trees were invented by Rudolf Bayer and Edward M. McCreight while working at Boeing Research Labs to efficiently manage index pages for large random-access files. The basic assumption was that indices would be so voluminous that only small chunks of the tree could fit in main memory.
Bagwell [1] presented a time and space efficient solution for tries named Array Mapped Tree (AMT). The Hash array mapped trie (HAMT) is based on AMT. The compact trie node representation uses a bitmap to mark every valid branch – a bitwise trie with bitmap.
A bitmap index is a special kind of indexing that stores the bulk of its data as bit arrays (bitmaps) and answers most queries by performing bitwise logical operations on these bitmaps. The most commonly used indexes, such as B+ trees, are most efficient if the values they index do not repeat or repeat a small number of times. In contrast, the ...
The structure at the top is a b-tree data structure and indexes the Employee ID column of the database table. The arrows point from the index value to the rows that contains the value in the "Employee ID" column. Btrieve uses a b-tree format to store record indexes on particular table columns.
Note (11): R-Tree indexing available in base edition with Locator but some functionality requires Personal Edition or Enterprise Edition with Spatial option. Note (12): FOT or Forest of Trees indexes is a type of B-tree index consisting of multiple B-trees which reduces contention in multi-user environments. [126]
The B+ tree is a structure for indexing single-dimensional data. In order to adopt the B+ tree as a moving object index, the B x-tree uses a linearization technique which helps to integrate objects' location at time t into single dimensional value. Specifically, objects are first partitioned according to their update time.
The simplest form of free-space bitmap is a bit array, i.e. a block of bits. In this example, a zero would indicate a free sector, while a one indicates a sector in use. Each sector would be of fixed size. For explanatory purposes, we will use a 4 GiB hard drive with 4096-byte sectors and