thiru

• Jun 25th, 2014

 

Using for low cardinality purpose

meera

• Apr 27th, 2015

 

Indexes in general speeds up the data retreival from database. Generally the index we use in OLTP or the operational database is B-Tree index.

But, Bitmap index is very much important in case of datawarehouse.

1) This type of index works for the columns having Low cardinality.
2) This works way faster than B-tree index.
3) This type of index works efficiently only when very update and delete operations or done,as it is very tedious work to update all the indexes accordingly every time update or delete is done.
4) The DWH environments typically have large amounts of data and ad hoc queries, but a low level of concurrent DML transactions.
Hence Bitmap indexes are widely used in data warehousing environments