Case insensitive parameters in Redash query result cache

[albrycht]

Issue Summary

Redash may display wrong results for query with case sensitive parameter. It looks like results cache is ignoring param letters size.

Steps to Reproduce

1. Create a query with global text parameter.
2. Create dashboard with visualization for this query.
3. Open dashboard with parameter set to lowercase letter for example 'test'
4. Open dashboard on a new tab with parameter 'TEST'.

In the last step you should receive visualization for parameter 'test' even when parameter value is set to 'TEST'

I have been able to reproduce this scenario on demo.redash.io. To reproduce do:

1. Open link: http://demo.redash.io/dashboard/ma_dashboard?p_dashboard_name=test
   You should see rows from dashboard table with name test
2. Open link: http://demo.redash.io/dashboard/ma_dashboard?p_dashboard_name=Test
   You should see rows from dashboard table with name test even when parameter dashboard_name is set to Test. After refreshing visualization result changed to proper one.

Technical details:

• Redash Version: 3.0.0+b3134
• Browser/OS: Chrome/Firefox/Opera
• How did you install Redash: used demo.redash.io

[arikfr]

The problem is in the redash.utils.gen_query_hash method. And it's actually documented there as a TODO item 😳

I think we can stop lower casing the query in this method. We don't need to dedup that aggressively.

[ClaudioDavi]

Hi, I've looked around at the code, reproduced the error and I think this can be my first PR.
@arikfr your suggestion is to remove the .lower() when we're creating the hash?

[arikfr]

@ClaudioDavi yes, but also need a migration to recalculate the query hash for all existing queries.

[ClaudioDavi]

Ok, thanks @arikfr ! Do you have any migration examples for me to have a look and follow through?