Hi,
I was reading through the new features of PG13 (beta), and noticed
that deduplication is disabled for float(4, 8) and numeric (and jsonb,
...) due to that the datums of those types could be not binary equal,
but equal according for the opclass used.
But, if the ordering of operator-class equal tuples is already
system-defined, could the physical ordering of index tuples in a btree
(with deduplication enabled for "unsafe" opclasses) be updated from
[index_columns, tid] to [index_columns,
image_compare(non_datum_equal_columns), tid], giving a stable sorting
of opclass-equal and image-equal values and enabling safe consistent
deduplication?
This need not be a default-on feature (opt-in would be fine, as I
guess it could have a performance penalty), but having the ability to
use btree index tuple deduplication for numeric, float and other data
types would count as a win in my book.
-Matthias