Best way to keep track of a sliced TOAST

Hi,

I've been reading about TOASTing and would like to modify how the slicing works by taking into consideration the type of the varlena field. These changes would support future implementations of type specific optimized TOAST'ing functions. The first step would be to add information to the TOAST so we know if it is sliced or not and by which function it was sliced and TOASTed. This information should not break the current on disk format of TOASTs. I had the idea of putting this information on the varattrib struct va_header, perhaps adding more bit layouts to represent sliced TOASTs. This idea, however, was pointed to me to be a rather naive approach. What would be the best way to do this?

Bruno Hass