> The fundamental problem is that you can't do it without adding at least
> 16 bytes, probably 20, to the size of an index tuple header. That would
> double the physical size of an index on a simple column (eg an integer
> or timestamp). The extra I/O costs and extra maintenance costs are
> unattractive to say the least. And it takes away some of the
> justification for the whole thing, which is that reading an index is
> much cheaper than reading the main table. That's only true if the index
> is much smaller than the main table ...
Well, the trick would be to have it specified per-index, then it's up to
the user whether it's faster or not...