remote protocol can require client to perform checkpoint of the WAL.
This PR supports that need in the sync-engine implementation
Reviewed-by: Preston Thorpe <preston@turso.tech>
Closes#2565
This PR fixes few issues in turso-sync-engine implementation:
1. One step of `pull` implementation works like this:
a. Start write WAL session
b. Revert local changes in WAL
c. Replay WAL frames from remote DB
d. Replay WAL frames produced by local changes applied to the remote
DB copy (`synced`)
My initial thinking was that by executing step (d) we will get the same
schema as before (with same schema cookie) and everything will be fine.
With more deep thinking we can see that it's not fine - as after step
(d) tables created locally can change their root pages (if they were
created locally, for example) - and DB will have "broken" schema
2. Sync engine execute few SQL statements and do not run them to
completion - which basically created "orphaned" locks
In order to fix (1) I decided to introduce another `conn_raw_api`
extension which allows to read and write schema cookie directly in the
transaction. So, the process described above adds step (e) which set
schema cookie to the value strictly greater than the value before.
In order to fix (2) I just fixed all places where statement were dropped
before running to completion.
These fixes are merged together because I explored them by fixing one
new test: `test_sync_single_db_many_pulls_big_payloads`
Closes#2561
Add support for schema changes and granular updates in the
`DatabaseTape` and turso-sync-engine
Now, schema changes made locally will be replicated to the remote too.
Also, `UPDATE`s made locally will touch only changed columns (before we
did `DELETE` + `INSERT` which can overwrite non-conflicting changes from
another device to the same row).
Note, that schema changes replication for now can be pretty dangerous,
as we can't extract proper schema at some moment in time from turso_cdc
and always use latest schema columns. This means that it's better to
avoid `ALTER TABLE ...` to be executed locally, but basic DDL like
`CREATE TABLE / CREATE INDEX / DROP TABLE / DROP INDEX` will work fine
(as columns only appear/disappear for schema in this case).
Closes#2540
