html_url,issue_url,id,node_id,user,created_at,updated_at,author_association,body,reactions,issue,performed_via_github_app
https://github.com/simonw/datasette/issues/283#issuecomment-781670827,https://api.github.com/repos/simonw/datasette/issues/283,781670827,MDEyOklzc3VlQ29tbWVudDc4MTY3MDgyNw==,9599,2021-02-18T22:16:46Z,2021-02-18T22:16:46Z,OWNER,"Demo is now live here: https://latest.datasette.io/_memory

The documentation is at https://docs.datasette.io/en/latest/sql_queries.html#cross-database-queries - it links to this example query: https://latest.datasette.io/_memory?sql=select%0D%0A++%27fixtures%27+as+database%2C+*%0D%0Afrom%0D%0A++%5Bfixtures%5D.sqlite_master%0D%0Aunion%0D%0Aselect%0D%0A++%27extra_database%27+as+database%2C+*%0D%0Afrom%0D%0A++%5Bextra_database%5D.sqlite_master","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",325958506,
https://github.com/simonw/datasette/issues/283#issuecomment-781665560,https://api.github.com/repos/simonw/datasette/issues/283,781665560,MDEyOklzc3VlQ29tbWVudDc4MTY2NTU2MA==,9599,2021-02-18T22:06:14Z,2021-02-18T22:06:14Z,OWNER,"The implementation in #1232 is ready to land. It's the simplest-thing-that-could-possibly-work: you can run `datasette one.db two.db three.db --crossdb` and then use the `/_memory` page to run joins across tables from multiple databases.

It only works on the first 10 databases that were passed to the command-line. This means that if you have a Datasette instance with hundreds of attached databases (see [Datasette Library](https://github.com/simonw/datasette/issues/417)) this won't be particularly useful for you.

So... a better, future version of this feature would be one that lets you join across databases on command - maybe by hitting `/_memory?attach=db1&attach=db2` to get a special connection.

Also worth noting: plugins that implement the [prepare_connection()](https://docs.datasette.io/en/stable/plugin_hooks.html#prepare-connection-conn-database-datasette) hook can attach additional databases - so if you need better, customized support for this one way to handle that would be with a custom plugin.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",325958506,
https://github.com/simonw/datasette/issues/283#issuecomment-781593169,https://api.github.com/repos/simonw/datasette/issues/283,781593169,MDEyOklzc3VlQ29tbWVudDc4MTU5MzE2OQ==,9599,2021-02-18T19:47:34Z,2021-02-18T19:47:34Z,OWNER,"I have a working version now, moving development to a pull request.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",325958506,
https://github.com/simonw/datasette/issues/283#issuecomment-781591015,https://api.github.com/repos/simonw/datasette/issues/283,781591015,MDEyOklzc3VlQ29tbWVudDc4MTU5MTAxNQ==,9599,2021-02-18T19:44:02Z,2021-02-18T19:44:02Z,OWNER,For the moment I'm going to hard-code a `SQLITE_LIMIT_ATTACHED=10` constant and only attach the first 10 databases to the `_memory` connection.,"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",325958506,
https://github.com/simonw/datasette/issues/283#issuecomment-781574786,https://api.github.com/repos/simonw/datasette/issues/283,781574786,MDEyOklzc3VlQ29tbWVudDc4MTU3NDc4Ng==,9599,2021-02-18T19:15:37Z,2021-02-18T19:15:37Z,OWNER,`select * from pragma_database_list();` is useful - shows all attached databases for the current connection.,"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",325958506,
https://github.com/simonw/datasette/issues/283#issuecomment-781573676,https://api.github.com/repos/simonw/datasette/issues/283,781573676,MDEyOklzc3VlQ29tbWVudDc4MTU3MzY3Ng==,9599,2021-02-18T19:13:30Z,2021-02-18T19:13:30Z,OWNER,"It turns out SQLite defaults to a maximum of 10 attached databases. This can be increased using a compile-time constant, but even with that it cannot be more than 62: https://stackoverflow.com/questions/9845448/attach-limit-10","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",325958506,
https://github.com/simonw/datasette/issues/283#issuecomment-781077127,https://api.github.com/repos/simonw/datasette/issues/283,781077127,MDEyOklzc3VlQ29tbWVudDc4MTA3NzEyNw==,9599,2021-02-18T05:56:30Z,2021-02-18T05:57:34Z,OWNER,I'm going to to try prototyping the `--crossdb` option that causes `/_memory` to connect to all databases as a starting point and see how well that works.,"{""total_count"": 1, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 1, ""eyes"": 0}",325958506,