* Fix commitlog `fold_transactions_from` ignoring requested offset
Prior to this commit, `fold_transactions_from` on a durability backed by a commitlog
would discard the requested offset and unconditionally yield all txes in the relevant segments.
This commit changes that behavior so that `fold_transactions_from`
skips commitlog commits (which contain many txes) less than the reqested offset,
and skips txes using `consume_record`.
* Add `Decoder::skip_record`
Lucky I asked Kim whether I was using `consume_record` and `decode_record` correctly,
because I wasn't.
This commit adds methods to `Decoder` and `Visitor` for skipping records and rows,
causing them to be extracted from the reader but not folded.
* Fix test
Add new methods to `Decoder` and `Visitor` hidden away in a test I missed.
The documentation promised to not collect payload values during folds
(i.e. replaying), but the code did so anyway. This patch makes it so
only values required to satisfy the `Visitor` trait are allocated when
folding.
Fix a minor bug where completely empty transactions would still be
written to the commitlog. The bug is minor because, once we start
logging inputs, all transactions will be non-empty.
The check is done in relational DB rather than the durability crate,
because in principle empty transactions are permissible, and may be used
in the future (e.g. to confirm a certain offset).
This patch attempts to integrate the new commitlog with the minimum
changes.
Most of the diff comes from deletions of the legacy log and the need to
adjust tests due to the requirement for a tokio runtime when a durable
database is used in tests.
The "meat" of the patch are the `RelationalDB` constructors,
`RelationalDB::commit_tx`, and the replay logic in
`locking_tx_datastore`.
While `DataKey` is gone, there is still some redundant data being passed
around, which will be addressed in the follow-up patch.
Defines the canonical commitlog payload, and how to encode / decode it.
Also exposes folds alongside iterators, which allows the common case of
replaying the commitlog onto a database to be further optimized (the
`Txdata` does not have to be constructed in this case). This
optimization is, however, left for a future patch.
Kim Altintop