Tomas Vondra <> writes:
> It would be really great if you could explain why BitmapScans are 
> dubious, instead of just labeling them as dubious. (I guess you mean 
> Bitmap Heap Scans, right?)

The two things I'm aware of are (a) the assumption you noted, that
fetching tuples in TID sort order is a reasonably efficient thing,
and (b) the "offset" part of a TID can't exceed MaxHeapTuplesPerPage
--- see data structure in tidbitmap.c.  The latter issue means that
you don't really have a full six bytes to play with in a TID, only
about five.

I don't think (b) would be terribly hard to fix if we had a motivation to,
but I wonder whether there aren't other places that also know this about

                        regards, tom lane

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