< * Use bitmaps to combine existing indexes [performance]
> * Allow the creation of bitmap indexes which can be quickly combined
>   with other bitmap indexes
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<   Bitmap indexes allow single indexed columns to be combined to
<   dynamically create a composite index to match a specific query. Each
<   index is a bitmap, and the bitmaps are AND'ed or OR'ed to be combined.
>   Bitmap indexes index single columns that can be combined with other bitmap
>   indexes to dynamically create a composite index to match a specific query.
>   Each index is a bitmap, and the bitmaps are bitwise AND'ed or OR'ed to be
>   combined.  Such indexes could be more compact if there are few unique
>   value.  Also, perhaps they can be lossy requiring a scan of the heap page
>   to find matching rows.
>
> * Allow non-bitmap indexes to be combined
>
>   Do lookups on non-bitmap indexes and create bitmaps in memory that can be
>   combined with other indexes.