Number-based alerts are broken

Issue Summary

It looks like the alert always sees a query result as a string and not a number. So an alert configured to trigger when field = 0 never triggers because "0" does not equal 0.

The alerts seems to evaluate fine for targets that are obviously strings. If the alert should trigger if field = boyhowdy then the alert triggers when field is “boyhowdy”.

Steps to Reproduce

1. Save a query that returns 0: SELECT 0 "value"
2. Make an alert for the query that triggers when value = 0
3. Run the query
4. Observe the alert does not trigger.

The converse is also true, by the way.

1. Same as above
2. Make an alert for the query that triggers when value != 0
3. Run the query
4. Observe the alert triggers

Technical details:

• Redash Version: 9.0.0-alpha+b348b58b (348b58b)
• Browser/OS: Firefox on MacOS
• How did you install Redash: SaaS

[ranbena]

Not sure about this, but perhaps we can hint at string values with apostrophes.

[arikfr]

I think that if query result is a number, then we should try to cast both to number. In other cases: use a string.

Because the operation options we show are based on the query result type, the threshold should adhere. We might want to enforce this in the UI.