Bitmap vs BTree

[Former Member]

SAP suggests that a bitmap index on a column can outperform a B-tree index when:

1. The Cardinality, which can be represented as the number of distinct values is small compared to the number of rows in the table. I can determine this via transaction DB02

2. Bitmap indexes are also ideal when values in a column are repeated more than 100. Can check this i.e. SE11

3. Where cardinality is high, bitmap indexes should be used if there are complex conditions in the WHERE clauses of queries. How can I determine this?

Thanks

[Former Member · Accepted solution]

Harpal,

The where clause of a query is dependent on what the user executes. So to make life a little easier, the decision point for using B-Tree ot Bitmap index is based on the number of values you expect in the dimension.

Non-line item dimensions - these should anyway be less than 10% of the fact table and hence B-TREE indexes don't make sense.

Line item dimensions with high number of unique values like document number should be marked as high cardinality. Line item dimensions with low number of repeat values should not be marked as high cardinality.

Cheers

Aneesh

[Former Member · Accepted solution]

Thanks Aneesh,

Have awarded points