bitmap indexの例文

• Variations on the bitmap index can effectively index this data as well.
• The Oracle implementation limits itself to using bitmap indexes.
• This is the simplest form of bitmap index.
• For example, using bitmap indexes, sorting can improve compression by an order of magnitude.
• Bitmap indexes have a significant space and performance advantage over other structures for query of such data.
• Each column in the left illustration is a " bitmap " in the bitmap index.
• For such variables, the bitmap index can have a significant performance advantage over the commonly used trees.
• Some database systems that do not offer persistent bitmap indexes use bitmaps internally to speed up query processing.
• In contrast, the bitmap index is designed for cases where the values of a variable repeat very frequently.
• Bitmap indexes use bit arrays ( commonly called bitmaps ) and answer queries by performing bitwise logical operations on these bitmaps.
• For example, PostgreSQL versions 8.1 and later implement a " bitmap index scan " optimization to speed up arbitrarily complex logical operations between available indexes on a single table.
• Efficient graph management based on bitmap indices article shows how bitmap index representation can be used to manage large dataset ( billions of data points ) and answer queries related to graph efficiently.
• 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.
• However, most compressed data formats are not so easy to access randomly; also by compressing bit arrays too aggressively we run the risk of losing the benefits due to bit-level parallelism ( Bitmap index ( compression ) ).
• Bitmap indexes have traditionally been considered to work well for " low-cardinality columns ", which have a modest number of distinct values, either absolutely, or relative to the number of records that contain the data.
• On the left, Identifier refers to the unique number assigned to each resident, HasInternet is the data to be indexed, the content of the bitmap index is shown as two columns under the heading " bitmaps ".
• For those who might be interested in experimenting with some of the ideas mentioned here, many of them are implemented in open source software such as FastBit, the Lemur Bitmap Index C + + Library, the Roaring Bitmap Java library, the Apache Hive Data Warehouse system and LucidDB.
• Some researchers argue that bitmap indexes are also useful for moderate or even high-cardinality data ( e . g ., unique-valued data ) which is accessed in a read-only manner, and queries access multiple bitmap-indexed columns using the AND, OR or XOR operators extensively.