[IMP] api, models: _write performances on import

Followup from the previous commit: before this, _write takes 32% of
total runtime, of which 13.7% is ultimately assignable to add_todo.

Turns out for the test case we mostly keep adding records to recorsets
where they're already present, so the 13.7% of runtime in add_todo are
mostly spent creating orderedsets (11.17) then converting those back
into recordsets (1.75%) with some time spent creating lists and
appending records (already present) in them.

Checking if the records are already present before merging them in
decreases add_todo's runtime cost to 0.5%, and ultimately _write to
20%.

As many of the ignorable calls were merging a singleton or an empty
recorset into the parent recordset, optimising for these cases was
added to BaseModel's <= and >=.

0 files changed, 0 insertions, 0 deletions