issue_comments

Awesome, thanks @brandonrobertz !

The plugin is close, but looks like it only grabs remote metadata, is that right? Instead what I'm wanting is to grab metadata embedded in the attached databases. Rather than extending that plugin, at this point I've realized I need a lot more flexibility in metadata for my data model (esp around formatting cell values and custom file exports) so rather than extending that I'll continue working on a plugin specific to my app.

If I'm understanding your plugin code correctly, you query the db using the sync handle every time get_metdata is called, right? Won't this become a pretty big bottleneck if a hook into render_cell is trying to read metadata / plugin config?

Making the get_metadata async won't improve the situation by itself as only some of the code paths accessing metadata use that hook. The other paths use the internal metadata dict.

I agree -- because things like render_cell will potentially want to read metadata/config, get_metadata should really remain sync and lightweight, which we can do with something like the remote-metadata plugin that could also poll metadata tables in attached databases.

That leaves your app, where it sounds like you want changes made by the user in the browser in to be immediately reflected, rather than have to wait for the next metadata refresh. In this case I wonder if you could have your app make a sync write to the datasette object so the change would have the immediate effect, but then have a separate async polling mechanism to eventually write that change out to the database for long-term persistence. Then you'd have the best of both worlds, I think? But probably not worth the trouble if your use cases are small (and/or you're not reading metadata/config from tight loops like render_cell).

Ok, I'm taking a slightly different approach, which I think is sort of close to the in-memory _metadata table idea.

I'm using a startup hook to load metadata / other info from the database, which I store in the datasette object for later:

@hookimpl def startup(datasette): async def inner(): datasette._mypluginmetadata = # await db query return inner

Then, I can use this in other plugins:

@hookimpl def render_cell(value, column, table, database, datasette): # use datasette._mypluginmetadata

For my app I don't need anything to update dynamically so it's fine to pre-populate everything on startup. It's also good to have things precached especially for a hook like render_cell, which would otherwise require a ton of redundant db queries.

Makes me wonder if we could take a sort of similar caching approach with the internal _metadata table. Like have a little watchdog that could query all of the attached dbs for their _metadata tables every 5min or so, which then could be merged into the in memory _metadata table which then could be accessed sync by the plugins, or something like that.

For most the use cases I can think of, live updates don't need to take into effect immediately; refreshing a cache every 5min or on some other trigger (adjustable w a config setting) would be just fine.