RE: BITMAP Versus B-TREE

Do you mean the column has only one value, including nulls? I wouldn't put an index on that.
Yes, bitmaps are great for queries but a pain for loading. They can also really favour certain access paths and I find a little "buggier". They can also grow like crazy.
I would say, if you heavily use bitmaps, it increases your administration. Like all things oracle, it's the details that kill you.

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