:db/tx (and Datomic's version, :datomic/tx) suffer from the same
ambiguities that [a v] lookup references do -- determining the type of
the result is context sensitive. (In this case, is :db/tx a reference
to the current transaction ID, or is it a valid keyword?) This commit
addresses the ambiguity by introducing a notion of a transaction
functions, and provides a little scaffolding for adding more (should
the need arise). I left the scaffolding in place rather than handling
just (transaction-tx) because I started trying to
implement (transaction-instant) as well, which is more difficult --
see the comments.
It's worth noting that this approach generalizes more or less directly
to ?input variables, since those can be eagerly bound like the
implemented transaction function (transaction-tx).
Also move `now` into core, implement microsecond truncation.
This is so we don't return a more granular -- and thus subtly different --
timestamp in a `TxReport` than we put into the store.
This is an optimization that trades rejecting inputs earlier at the
cost of expressive error messages. It should be possible to recover
the error messages, however.
This will reject input like `[:db/{add,retract} v :attribute/_reversed NOT-AN-ENTITY]`.
This is a big commit, but it breaks into two conceptual pieces. The
first is to "parse without copying". We replace a stream of an owned
collection of edn::ValueAndSpan and instead have a stream of a
borrowed collection of &edn::ValueAndSpan references. (Generally,
this is represented as an iterator over a slice, but it can be over
other things too.) Cloning such iterators is constant time, which
improves on cloning an owned collection of edn::ValueAndSpan, which is
linear time in the length of the collection and additional time
depending on the complexity of the EDN values.
The second conceptual piece is to parse keyword maps using a special
parser and a macro to build the parser implementations. Before, we
created a new edn::ValueAndSpan::Map to represent a keyword map in
vector form; since we're working with &edn::ValueAndSpan references
now, we can't create an &edn::ValueAndSpan reference with an
appropriate lifetime. Therefore we generalize the concept of
iteration slightly and turn keyword maps in map form into linear
iterators by flattening the value maps. This is a potentially
obscuring transformation, so we have to take care to protect against
some failure cases. (See the comments and the tests in the code.)
After these changes, parsing using `combine` is linear time (and
reasonably fast).
* Pre: Expose more in edn.
* Pre: Make it easier to work with ValueAndSpan.
with_spans() is a temporary hack, needed only because I don't care to
parse the bootstrap assertions from text right now.
* Part 1a: Add `value_and_span` for parsing nested `edn::ValueAndSpan` instances.
I wasn't able to abstract over `edn::Value` and `edn::ValueAndSpan`;
there are multiple obstacles. I chose to roll with
`edn::ValueAndSpan` since it exposes the additional span information
that we will want to form good error messages in the future.
* Part 1b: Add keyword_map() parsing an `edn::Value::Vector` into an `edn::Value::map`.
* Part 1c: Add `Log`/`.log(...)` for logging parser progress.
This is a terrible hack, but it sure helps to debug complicated nested
parsers. I don't even know what a principled approach would look
like; since our parser combinators are so frequently expressed in
code, it's hard to imagine a data-driven interpreter that can help
debug things.
* Part 2: Use `value_and_span` apparatus in tx-parser/.
I break an abstraction boundary by returning a value column
`edn::ValueAndSpan` rather than just an `edn::Value`. That is, the
transaction processor shouldn't care where the `edn::Value` it is
processing arose -- even we care to track that information we should
bake it into the `Entity` type. We do this because we need to
dynamically parse the value column to support nested maps, and parsing
requires a full `edn::ValueAndSpan`. Alternately, we could cheat and
fake the spans when parsing nested maps, but that's potentially
expensive.
* Part 3: Use `value_and_span` apparatus in query-parser/.
* Part 4: Use `value_and_span` apparatus in root crate.
* Review comment: Make Span and SpanPosition Copy.
* Review comment: nits.
* Review comment: Make `or` be `or_exactly`.
I baked the eof checking directly into the parser, rather than using
the skip and eof parsers. I also took the time to restore some tests
that were mistakenly commented out.
* Review comment: Extract and use def_matches_* macros.
* Review comment: .map() as late as possible.
* Pre: Fix error in parser macros.
* Pre: Make test unwrapping more verbose.
* Pre: Make lookup refs be (lookup-ref a v) in the entity position.
This has the advantage of being explicit in all situations and
unambiguous at parse-time. This choice agrees with the Clojure
implementation but not with Datomic. Datomic treats [a v] as a lookup
ref, is ambiguous at parse-time, and is disambiguated in ways I do not
understand at transaction time. We mooted making lookup refs [[a v]]
and outlawing nested value vectors in transactions, but after
implementing that approach I decided it was better to handle lookup
refs at parse time and therefore outlawing nested value vectors is not
necessary.
* Handle lookup refs in the entity and value columns. Fixes#183.
* Pre 0a: Use a stack instead of into_iter.
* Pre 0b: Dedent.
* Pre 0c: Handle `e` after `v`.
This allows to use the original `e` while handling `v`.
* Explode value lists for :db.cardinality/many attributes. Fixes#284.
* Parse and accept map notation. Fixes#180.
* Pre: Modernize add() and retract() into one add_or_retract().
* Pre: Add is_collection and is_atom to edn::Value.
* Pre: Differentiate atoms from lookup-refs in value position.
Initially, I expected to accept arbitrary edn::Value instances in the
value position, and to differentiate in the transactor. However, the
implementation quickly became a two-stage parser, since we always
wanted to parse the resulting value position into some other known
thing using the tx-parser. To save calls into the parser and to allow
the parser to move forward with a smaller API surface, I push as much
of this parsing as possible into the initial parse.
* Pre: Modernize entities().
* Pre: Quote edn::Value::Text in Display.
* Review comment: Add and use edn::Value::into_atom.
* Review comment: Use skip(eof()) throughout.
* Review comment: VecDeque instead of Vec.
* Review comment: Part 0: Rename TempId to TempIdHandle.
* Review comment: Part 1: Differentiate internal and external tempids.
This breaks an abstraction boundary by pushing the Internal/External
split up to the Entity level in tx/ and tx-parser/. This just makes
it easier to explode Entity map notation instances into Entity
instances, taking an existing External tempid :db/id or generating a
new Internal tempid as appropriate. To do this without breaking the
abstraction boundary would require adding flexibility to the
transaction processor: we'd need to be able to turn Entity instances
into some internal enum and handle the two cases independently. It
wouldn't be too hard, but this reduces the combinatorial type
explosion.
* Pre: Drop unneeded tx0 from search results.
* Pre: Don't require a schema in some of the DB code.
The idea is to separate the transaction applying code, which is
schema-aware, from the concrete storage code, which is just concerned
with getting bits onto disk.
* Pre: Only reference Schema, not DB, in debug module.
This is part of a larger separation of the volatile PartitionMap,
which is modified every transaction, from the stable Schema, which is
infrequently modified.
* Pre: Fix indentation.
* Extract part of DB to new SchemaTypeChecking trait.
* Extract part of DB to new PartitionMapping trait.
* Pre: Don't expect :db.part/tx partition to advance when tx fails.
This fails right now, because we allocate tx IDs even when we shouldn't.
* Sketch a db interface without DB.
* Add ValueParseError; use error-chain in tx-parser.
This can be simplified when
https://github.com/Marwes/combine/issues/86 makes it to a published
release, but this unblocks us for now. This converts the `combine`
error type `ParseError<&'a [edn::Value]>` to a type with owned
`Vec<edn::Value>` collections, re-using `edn::Value::Vector` for
making them `Display`.
* Pre: Accept Borrow<Schema> instead of just &Schema in debug module.
This makes it easy to use Rc<Schema> or Arc<Schema> without inserting
&* sigils throughout the code.
* Use error-chain in query-parser.
There are a few things to point out here:
- the fine grained error types have been flattened into one crate-wide
error type; it's pretty easy to regain the granularity as needed.
- edn::ParseError is automatically lifted to
mentat_query_parser::errors::Error;
- we use mentat_parser_utils::ValueParser to maintain parsing error
information from `combine`.
* Patch up top-level.
* Review comment: Only `borrow()` once.
* Pre: Implement batch [a v] pair lookup.
* Pre: Add InternSet for sharing ref-counted handles to large values.
* Pre: Derive more for Entity.
* Pre: Return DB from creating; return TxReport from transact.
I explicitly am not supporting opening existing databases yet, let
alone upgrading databases from earlier versions. That can follow fast
once basic transactions are supported.
* Pre: Parse string temporary ID entities; remove ValueOrLookupRef.
This adds TempId entities, but we can't disambiguate String temporary
IDs from values without the use of the schema, so there's no new value
branch. Similarly, we can't disambiguate lookup-ref values from two
element list values without a schema, so we remove this entirely.
We'll handle the ambiguity later in the transactor.
* Persist partitions to SQL store; allocate transaction ID. (#186)
* Post: Test upserting with vectors.
This converts an existing test to EDN:
84a80f40f5/test/datomish/db_test.cljc (L193).
* Implement tempid upsert resolution algorithm. (#184)
* Post: Separate Tx out of DB.
This is very preliminary, since we don't have a real connection type
to manage transactions and their metadata yet.
* Post: Comment on implementation choices in the transactor.
* Review comment: Put long use lists on separate lines.
* Review comment: Accept String: Borrow<S> instead of just String.
* Review comment: Address nits.
