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0d17d35ef4
This PR add basic CDC functionality to the `turso-db`.
### Feature components
1. `unstable_capture_data_changes_conn` pragma which allow user to turn
on/off CDC logging for **specific connection**
* CDC will have multiple modes, but for now only `off` / `rowid-
only` are supported
* Default CDC table is `turso_cdc` but user can override this with
`PRAGMA` update syntax and use arbitrary table for the CDC needs
* This can be helpful in future if turso will need to break table
format compatibility and custom tables can be a way to migrate between
different schemas
* Update syntax for the pragma accepts one string argument in
format, where only mode is set or custom cdc table name is provided as
second part of the string, separated with comma from the mode
```sql
turso> PRAGMA unstable_capture_data_changes_conn('rowid-only');
turso> PRAGMA unstable_capture_data_changes_conn('off');
turso> PRAGMA unstable_capture_data_changes_conn('rowid-only,custom_cdc_table');
turso> PRAGMA unstable_capture_data_changes_conn;
┌────────────┬──────────────────┐
│ mode │ table │
├────────────┼──────────────────┤
│ rowid-only │ custom_cdc_table │
└────────────┴──────────────────┘
```
2. CDC table schema right now is simple but it will be evolved soon to
support logging of row values before/after the change:
```sql
CREATE TABLE custom_cdc_table (
operation_id INTEGER PRIMARY KEY AUTOINCREMENT,
operation_time INTEGER, -- unixepoch() at the moment of insert, can drift if machine clocks is not monotonic
operation_type INTEGER, -- -1 = delete, 0 = update, 1 = insert
table_name TEXT,
id
)
```
* Note, that `operation_id` is marked as `AUTOINCREMENT` but `turso-
db` needs to implement
https://github.com/tursodatabase/turso/issues/1976 in order to properly
support that keyword
3. Query planner changes are made in `INSERT`/`UPDATE`/`DELETE` plans in
order to emit updates to the CDC table for changes in the table
* Note, that row `UPDATE` which change primary key generate `DELETE` +
`INSERT` statement instead of single `UPDATE`
### Implementation details
- `PRAGMA` to enable CDC is **unstable** which means that publicly
visible side-effects/public API can change in future (and it will change
soon in order to support more rich CDC modes)
- CDC table is just a regular table with its benefits and downsides:
* benefits: user can perform maintenance operations with that table
just with regular SQL like `DELETE FROM turso_cdc WHERE operation_id <
?` to cleanup old not needed CDC entries
* downsides: user can accidentally make unwanted change to CDC table
- Changes to CDC table is not logged to itself
* Note, that different connections (e.g. `C1`, `C2`) can have
different CDC tables set (e.g. `A` and `B`) - in which case changes made
to CDC table `B` through connection `C1` will be reflected in CDC table
`A`
Reviewed-by: Pere Diaz Bou <pere-altea@homail.com>
Closes #1926