Simon Riggs wrote:
I don't believe that read only is required. The update/insert performance impact of bimap indexes is however very high (in Oracle's implementation anyway) - to the point where many sites drop them before adding in new data, and recreated 'em afterwards!
I believe that the benefit of on-disk bitmap indexes is supposed to be reduced storage size (compared to btree).
The main problem is the need for the table to be read-only. Until we have partitioning, we wouldn't be able to easily guarantee parts of a table as being (effectively) read-only.
In the advent that there is a benefit for the small on-disk footprint, the insert/update throughput implications will need to be taken into account.
cheers
Mark
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TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match
