`find()` with no sort now returns documents in insertion order
Summary: find() with no sort now returns documents in insertion order (v0.5.3b13).
An unsorted find() now returns documents in insertion order, matching
mongod's natural (storage) order. Previously SecantusDB returned them in _id
order — which coincides with insertion order for the default monotonic
ObjectId _ids, but diverged whenever a collection mixed _id types or used
non-monotonic _ids (an int 1, a string "foo", a sub-document — BSON sorts
those very differently from the order you inserted them). Code and drivers that
read back rows in the order they were written — a common, reasonable assumption
that mongod honours — now see the same order here.
Internally this adds a small natural-order index (a monotonic insertion sequence
→ document map) that an unsorted scan and the $natural hint walk; the document
store itself is unchanged, so every _id lookup, secondary index, and
uniqueness check is untouched. Capped-collection eviction and equal-key sort
tie-breaks also follow insertion order now. (Multi=false updateOne/deleteOne
without a sort still pick the _id-order-first match rather than the
insertion-first one — a smaller remaining divergence, tracked in the backlog.)