Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A bitmap index is a special kind of database index that uses bitmaps. Bitmap indexes have traditionally been considered to work well for data such as gender, which has a small number of distinct values, for example male and female, but many occurrences of those values. This would happen if, for example, you had gender data for each resident in a city. Bitmap indexes have a significant space and performance advantage over other structures for such data. However, some researchers argue that Bitmap indexes are also useful for unique valued data which is not updated frequently. Bitmap indexes use bit arrays (commonly called bitmaps) and answer queries by performing bitwise logical operations on these bitmaps.

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