issue_comments: 1258167564

reading the database execute method i have a few questions.

https://github.com/simonw/datasette/blob/cb1e093fd361b758120aefc1a444df02462389a3/datasette/database.py#L229-L242

unless i'm missing something (which is very likely!!), the max_returned_rows argument doesn't actually offer any protections against running very expensive queries.

It's not like adding a LIMIT max_rows argument. it make sense that it isn't because, the query could already have an LIMIT argument. Doing something like select * from (query) limit {max_returned_rows} might be protective but wouldn't always.

Instead the code executes the full original query, and if still has time it fetches out the first max_rows + 1 rows.

this does offer some protection of memory exhaustion, as you won't hydrate a huge result set into python (however, there are data flow patterns that could avoid that too)

given the current architecture, i don't see how creating a new connection would be use?

If we just removed the max_return_rows limitation, then i think most things would be fine except for the QueryViews. Right now rendering, just 5000 rows takes a lot of client-side memory so some form of pagination would be required.