Pre: export AttributeBuilder from mentat_db.
Pre: fix module-level comment for tx/src/entities.rs.
Pre: rename some `to_` conversions to `into_`.
Pre: make AttributeBuilder::unique less verbose.
Pre: split out a HasSchema trait to abstract over Schema.
Pre: rename SchemaMap/schema_map to AttributeMap/attribute_map.
Pre: TypedValue/NamespacedKeyword conversions.
Pre: turn Unique and ValueType into TypedValue::Keyword.
Pre: export IntoResult.
Pre: export NamespacedKeyword from mentat_core.
Pre: use intern_set in tx.
Pre: add InternSet::len.
Pre: comment gardening.
Pre: remove inaccurate TODO from TxReport comment.
This version removes nalexander's lovely matrix code. It turned out
that scalar and tuple bindings are sufficiently different from coll
and rel -- they can directly apply as values in the query -- that
there was no point in jumping through hoops to turn those single
values into a matrix.
Furthermore, I've standardized us on a Vec<TypedValue>
representation for rectangular matrices, which should be much
more efficient, but would have required rewriting that code.
Finally, coll and rel are sufficiently different from each other
-- coll doesn't require processing nested collections -- that
my attempts to share code between them fell somewhat flat. I had
lots of nice ideas about zipping together cycles and such, but
ultimately I ended up with relatively straightforward, if a bit
repetitive, code.
The next commit will demonstrate the value of this work -- tests
that exercised scalar and tuple grounding now collapse down to
the simplest possible SQL.
