That seems like your RDBMS wasn't handling something right there or there wasn't a unique index on the column.

Do you recall what the database server was?

Yes, I was using Mysql exclusively at the time. I don't recall which version.

I also tested this once years later when doing a Python app with sqlite. Similar result, but admittedly that was not a very big table to begin with.

I am meticulous with my database schemas, and periodically review my indexes and covering indexes. I'm no DBA, but I believe that the database is the only real value a codebase has, other than maybe a novel method here and there. So I put care into designing it properly and testing my assumptions.

You should use the DB explain or equivalent command to spit out the query plan, limit 1 shouldn't change anything in your case, if it's not the case you should file an issue, it's pretty much 101 of query optimization.

That would be a reportable bug. Of a pretty high priority.

You are certainly doing something wrong if that's true.

I'm curious, can you demo this?

I'm curious as well to see if this still holds up. I'll try this week.