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Home -> Community -> Usenet -> c.d.o.server -> Re: Strange CBO Behaviour with a Bitmap Index
Okay, I was wondering if it might be an architectural issue. Bitmap
indexes are not something I've got a lot of experience with. I was
concerned about the impact of DML on the index (which is why I'm
benchmarking this very carefully), but thought I might be able to get
away with it as there will be no DML of the OLTP variety on the table
concerned. Obviously, I cannot use this index in the way I originally
intended, which is a shame but hey-ho.
Unfortunately, I still need to find a way to retrieve the desired columns without having to resort to a Full Table Scan. I think what I'm going to do is create a global binary tree index on the REPORT_POPULATED column. I know the CBO won't elect to use this, which suits me fine because I need the query to descending scan the index anyway, so will have to use a hint to force this behaviour.
The most recent entries in this table will be at the end of it, as it only takes inserts in ascending date order, and the REPORT_POPULATED = 'Y' rows will be the most recent. A descending binary tree index scan might work. Only one way to find out............... Received on Wed Feb 01 2006 - 07:48:08 CST