Check and SHOW WARNINGS in Mysql

[TheLQ]

Backend

MySQL

What do you want to add to diesel?

There's a non-zero chance mysql queries have warnings. Expect in hand built queries or oddly configured servers. But there's no way to know: SHOW WARNINGS and SELECT @@warning_count is not supported in prepared statements, running them in batch_query / RawConnection::execute throws the result away.

For reference, mysql Connector/python calls mysql_warnings_count() after every query. If any they SHOW WARNINGS then log or throw an exception. Connector/j has a similar system.

Implementation notes

I implemented a basic version with the non-prepared statement API. TheLQ@f67fabd

Calling after my questionable batch_query found real problems: data truncation because I wrote the LOAD DATA file wrong (dates aren't quoted, null is \N not NULL, oops...), duplicate primary keys from bad cleanup. Again before I had no errors and no logs only confusing table output.

Looking for feedback before submitting a PR: Is there interest in warnings checks? Would you want an automatic Err-on-warning like the connector clients or only explicit mysql_warnings_count() + SHOW WARNINGS? Any implementation suggestions styling wise?

Additional details

No response

Checklist

• I have already looked over the issue tracker and the discussion forum for similar possible closed issues.

[weiznich]

First of all: I'm sorry to let your proposal sit that long unanswered, it's just currently hard to get through all the issues, PR's and suggestions in a timely manner in the time I have to work on the project.

That out of the way: I would be generally open to expose this. The proposed API looks mostly fine to me, although I would expect at least some tests + a bit of documentation. As for the actual implementation: I've added a bunch of comments to your commit, hopefully that's helpful. (It's mostly minor style suggestions instead problems with the implementation)