refactor: Removes the deprecated DASHBOARD_CACHE feature flag

[michael-s-molina]

SUMMARY

As part of the 4.0 approved initiatives, this PR removes the DASHBOARD_CACHE feature flag.

The previous value of the feature flag was False and now the feature is permanently removed.

TESTING INSTRUCTIONS

CI should be sufficient for merging this PR. We'll do a complete testing of 4.0 after all approved proposals are merged.

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (9387c4c) 66.85% compared to head (11c10e4) 66.88%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #26349      +/-   ##
==========================================
+ Coverage   66.85%   66.88%   +0.02%     
==========================================
  Files        1931     1938       +7     
  Lines       75355    75505     +150     
  Branches     8431     8467      +36     
==========================================
+ Hits        50378    50499     +121     
- Misses      22829    22847      +18     
- Partials     2148     2159      +11     

Flag	Coverage Δ
mysql	77.88% <100.00%> (+0.02%)	⬆️
postgres	78.01% <100.00%> (+0.02%)	⬆️
python	78.15% <100.00%> (+0.02%)	⬆️
sqlite	77.59% <100.00%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[john-bodley]

What are the consequences of removing the cache? Is there merit in expanding why this was removed?

[michael-s-molina]

I think this feature never worked correctly. It was Airbnb who introduced it and quickly disabled it because of problems reported by users while using the dashboards.

[mistercrunch]

Getting an error trying to delete a dashboard in the UI and thought it may be related:

Traceback (most recent call last):
  File "/Users/max/.pyenv/versions/3.9.16/envs/superset/lib/python3.9/site-packages/flask_appbuilder/api/__init__.py", line 110, in wraps
    return f(self, *args, **kwargs)
  File "/Users/max/code/superset/superset/views/base_api.py", line 127, in wraps
    raise ex
  File "/Users/max/code/superset/superset/views/base_api.py", line 121, in wraps
    duration, response = time_function(f, self, *args, **kwargs)
  File "/Users/max/code/superset/superset/utils/core.py", line 1454, in time_function
    response = func(*args, **kwargs)
  File "/Users/max/code/superset/superset/utils/log.py", line 255, in wrapper
    value = f(*args, **kwargs)
  File "/Users/max/code/superset/superset/charts/api.py", line 459, in delete
    DeleteChartCommand([pk]).run()
  File "/Users/max/code/superset/superset/commands/chart/delete.py", line 50, in run
    Dashboard.clear_cache_for_slice(slice_id=model_id)
  File "/Users/max/code/superset/superset/utils/decorators.py", line 180, in wrapped
    result = f(*args, **kwargs)
  File "/Users/max/code/superset/superset/models/dashboard.py", line 336, in clear_cache_for_slice
    cls(id=dashboard_id).clear_cache()
  File "/Users/max/code/superset/superset/utils/decorators.py", line 180, in wrapped
    result = f(*args, **kwargs)
  File "/Users/max/code/superset/superset/models/dashboard.py", line 327, in clear_cache
    cache_manager.cache.delete_memoized(Dashboard.datasets_trimmed_for_slices, self)
  File "/Users/max/.pyenv/versions/3.9.16/envs/superset/lib/python3.9/site-packages/flask_caching/__init__.py", line 1020, in delete_memoized
    cache_key = f.make_cache_key(f.uncached, *args, **kwargs)
AttributeError: 'function' object has no attribute 'make_cache_key'

[mistercrunch]

checking out the SHA right before this got merged in master fixes the issue @michael-s-molina @eschutho

[michael-s-molina]

Getting an error trying to delete a dashboard in the UI and thought it may be related:

Thanks for reporting the issue @mistercrunch. I opened #26648 to fix it.