id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,pull_request,body,repo,type,active_lock_reason,performed_via_github_app,reactions,draft,state_reason
316621102,MDU6SXNzdWUzMTY2MjExMDI=,235,Add limit on the size in KB of data returned from a single query,9599,open,0,,,2,2018-04-22T23:01:15Z,2018-04-24T00:30:02Z,,OWNER,,"Datasette limits the number of rows returned to 1,000 and limits the time spent executing a SQL query to 1000ms - and both of these limits can be customized.

It does not have a limit on the size of the response returned. It's possible to compose maliciously large SQL responses in a small number of rows using mechanisms like the `group_concat()` aggregate function. It would be good to avoid malicious SQL creating 100MB+ responses and potentially crashing the server.

I think the easiest place to implement that is here:

https://github.com/simonw/datasette/blob/f3f42957128c1e7ece584d45d9167f2ac003a3b8/datasette/app.py#L175-L190

Currently we use `cursor.fetchmany()` to fetch up to 1,001 rows at once. Instead, we could switch to iterating through `cursor.fetchone()` (or just using `for row in cursor`) and keeping a running tally of the size of the response as we go - maybe just using `rough_response_size += len(str(row))`. If that goes above a certain threshold we can terminate the response with an error, like we do with timelimits.

The bigger challenge here is understanding how well this approach works and what impact it will have on overall Datasette performance. I think I need #33 for this.",107914493,issue,,,"{""url"": ""https://api.github.com/repos/simonw/datasette/issues/235/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,