This PR introduces few sync fixes relevant to the partial sync feature:
1. Make `try_wal_watermark_read_page` async - this is important as now
db file can be partial and require extra network IO for fetching missing
pages
2. Do not panic if requested page doesn't exist on server - this can be
valid case if db on the server has smaller size
3. Maintain clean db file size in order to avoid reads outside of the
file (this can happen, when we revert new pages allocated only in the
WAL and need to fetch their previous state if there is one)
Reviewed-by: Preston Thorpe <preston@turso.tech>
Closes#4297
The DX is right now pretty terrible:
```
penberg@vonneumann turso % cargo run -- hello.db
Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.15s
Running `target/debug/tursodb hello.db`
Turso v0.4.0-pre.18
Enter ".help" for usage hints.
Did you know that Turso supports live materialized views? Type .manual materialized-views to learn more.
This software is in BETA, use caution with production data and ensure you have backups.
turso> PRAGMA journal_mode = 'experimental_mvcc';
× Invalid argument supplied: MVCC is not enabled. Enable it with `--experimental-mvcc` flag in the CLI or by setting the MVCC option in `DatabaseOpts`
turso>
```
To add insult to the injury, many SDKs don't even have a way to enable
MVCC via database options. Therefore, let's remove the flag altogether.
Reviewed-by: Jussi Saurio <jussi.saurio@gmail.com>
Closes#4294
The DX is right now pretty terrible:
```
penberg@vonneumann turso % cargo run -- hello.db
Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.15s
Running `target/debug/tursodb hello.db`
Turso v0.4.0-pre.18
Enter ".help" for usage hints.
Did you know that Turso supports live materialized views? Type .manual materialized-views to learn more.
This software is in BETA, use caution with production data and ensure you have backups.
turso> PRAGMA journal_mode = 'experimental_mvcc';
× Invalid argument supplied: MVCC is not enabled. Enable it with `--experimental-mvcc` flag in the CLI or by setting the MVCC option in `DatabaseOpts`
turso>
```
To add insult to the injury, many SDKs don't even have a way to enable
MVCC via database options. Therefore, let's remove the flag altogether.
This PR implements basic support for partial sync. Right now the scope
is limited to only `:memory:` IO and later will be properly expanded to
the file based IO later.
The main addition is `PartialDatabaseStorage` which make request to the
remote server for missing local pages on demand.
The main change is that now tursodatabase JS bindings accept optional
"external" IO event loop which in case of sync will drive `ProtocolIo`
internal work associated with remote page fetching tasks.
Closes#3931
- before we fetched pull generation and last_change_id from the remote during pull - which is incorrect because fetched information can be inconsistent with WAL updates we received from the server (latest server state can be in "future" compared to the WAL updates we got since we can make push in parallel with updates pull operation)
- now we read information about "server state" (pull generation, last_change_id) directly from the local DB right after we applied changes from the remote which get us consistent view on the state considering WAL updates we got
- also fetching remote in the pull is bad - since pull block writes and network call with unpredictable latency poorly affect writes to the database
