Peter Geoghegan <pg@bowt.ie> writes:
> The heapallindexed enhancement that made it into Postgres 11 assumes
> that the representation of index tuples produced by index_form_tuple()
> (or all relevant index_form_tuple() callers) is deterministic: for
> every possible heap tuple input there must be a single possible
> (bitwise) output.
That assumption seems unbelievably fragile. How badly do things
break when it's violated?
Also, is the assumption just that a fixed source tuple will generate
identical index entries across repeated index_form_tuple attempts?
Or is it assuming that logically equal index entries will be bitwise
equal? The latter is broken on its face, because index_form_tuple()
doesn't try to hide differences in the toasting state of source
datums.
regards, tom lane