presto error messages are hard to read

[cldellow]

Issue Summary

Errors for the presto query runner produce a hard-to-read stringified JSON blob, e.g.:

It'd probably be useful to just have the embedded message field instead of the entire thing -- the JSON escaping and and Presto stack trace are rarely relevant to the user.

Steps to Reproduce

1. Run a query that will fail, e.g. 'SELECT foo FROM bar WHERE baz = 1'

Technical details:

• Redash Version: 0.12.0+b2449

[cldellow]

Note, an easy "fix" is to patch query_runner/presto.py and add:

if type(error) is dict and 'failureInfo' in error and 'message' in error['failureInfo']:
    error = error['failureInfo']['message']

to pull our the error message.

Then you get error messages like:

That feels kinda hacky though -- maybe there's a reason the fuller blob is being sent? If not, I can put together a PR that makes this change.

[arikfr]

This definitely looks nicer! But I agree that the implementation feels hacky. The snippet you posted on what line in preto.py does it belong?

[cldellow]

It would go here: https://github.com/getredash/redash/blob/master/redash/query_runner/presto.py#L117

[arikfr]

Maybe to make it less hacky we catch a more specific exception class there rather than just Exception?

[aslotnick]

@arikfr I think this PR should address this issue - anything I should change? I've provided a default and caught the specific exception (DatabaseError) but the overall effect is the same as what @cldellow has proposed.

[arikfr]

Thanks @aslotnick ! Merged.

[aslotnick]

Thank you, @arikfr ! Happy to finally contribute.