pgsql: Update: < * Use bitmaps to combine existing indexes

Log Message:
-----------
Update:

< * Use bitmaps to combine existing indexes [performance]
> * Allow the creation of bitmap indexes which can be quickly combined
> with other bitmap indexes
255,257c256,266
< 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.

Modified Files:
--------------
pgsql/doc:
TODO (r1.1376 -> r1.1377)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.1376&r2=1.1377)