issues: 1870672704
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| 1870672704 | PR_kwDOBm6k_c5Y-7Em | 2162 | Add new `--internal internal.db` option, deprecate legacy `_internal` database | 15178711 | closed | 0 | 4 | 2023-08-29T00:05:07Z | 2023-08-29T03:24:23Z | 2023-08-29T03:24:23Z | CONTRIBUTOR | simonw/datasette/pulls/2162 | refs #2157 This PR adds a new `--internal` option to datasette serve. If provided, it is the path to a persistent internal database that Datasette core and Datasette plugins can use to store data, as discussed in the proposal issue. This PR also removes and deprecates the previous in-memory `_internal` database. Those tables now appear in the `internal` database, with `core_` prefixes (ex `tables` in `_internal` is now `core_tables` in `internal`). ## A note on the new `core_` tables However, one important notes about those new `core_` tables: If a `--internal` DB is passed in, that means those `core_` tables will persist across multiple Datasette instances. This wasn't the case before, since `_internal` was always an in-memory database created from scratch. I tried to put those `core_` tables as `TEMP` tables - after all, there's always one 1 `internal` DB connection at a time, so I figured it would work. But, since we use the `Database()` wrapper for the internal DB, it has two separate connections: a default read-only connection and a write connection that is created when a write operation occurs. Which meant the `TEMP` tables would be created by the write connection, but not available in the read-only connection. So I had a brillant idea: Attach an in-memory named database with `cache=shared`, and create those tables there! ```sql ATTACH DATABASE 'file:datasette_internal_core?mode=memory&cache=shared' AS core; ``` We'd run this on both the read-only connection and the write-only connection. That way, those tables would stay in memory, they'd communicate with the `cache=shared` feature, and we'd be good to go. However, I couldn't find an easy way to run a `ATTACH DATABASE` command on the read-only query. Using `Database()` as a wrapper for the internal DB is pretty limiting - it's meant for Datasette "data" databases, where we want multiple readers and possibly 1 write connection at a time. But the internal database doesn't really require that kind of support - I think we could get away with a single read/write connection, but it seemed like too big of a rabbithole to go through now. <!-- readthedocs-preview datasette start --> ---- :books: Documentation preview :books:: https://datasette--2162.org.readthedocs.build/en/2162/ <!-- readthedocs-preview datasette end --> | 107914493 | pull | {"url": "https://api.github.com/repos/simonw/datasette/issues/2162/reactions", "total_count": 0, "+1": 0, "-1": 0, "laugh": 0, "hooray": 0, "confused": 0, "heart": 0, "rocket": 0, "eyes": 0} | 0 |