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