On Oracle 10g
I'm running some benchmark tests regarding the differences between the two types of indexes: Btree and Bitmap.
I have created a table with 15,000,000 rows that occupies around 2 Gigabyte.
I have create 5 different indexes with the following number of distinct keys:
15,000,000 distinct keys.
1. I have created these indexes once in Btree mode and once in Bitmap mode.
2. I executed around 5,000 queries, 1000 updates and delete against each index in each mode.
3. I have execute a 20 end users concurrent updates against the 100,000 keys index
There are very minor changes in performance.
The only main difference is the size of the index. The Btree is much smaller: between 4 to 40 times smaller than the Btree index.
Now, my question is, Have I forgot any tests here? Did you ever get different results? Is there a hidden problem with the Bitmap indexes that would make them unsuitable for OLTP environment?