Pass granularity from backend to frontend as ISO duration

[betodealmeida]

Currently the backend will pass the granularity as a string that is engine dependent, e.g, "30 seconds". I changed the backend so that an ISO 8601 duration is passed instead. This allows the frontend to handle the granularity better, eg, for the play slider.

[codecov-io]

Codecov Report

Merging #4755 into master will decrease coverage by 0.04%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #4755      +/-   ##
==========================================
- Coverage   72.38%   72.33%   -0.05%     
==========================================
  Files         205      205              
  Lines       15374    15394      +20     
  Branches     1182     1182              
==========================================
+ Hits        11128    11136       +8     
- Misses       4243     4255      +12     
  Partials        3        3

Impacted Files	Coverage Δ
...set/assets/javascripts/explore/stores/controls.jsx	39.25% <ø> (ø)	⬆️
superset/db_engine_specs.py	51.89% <100%> (ø)	⬆️
superset/models/core.py	86.52% <100%> (ø)	⬆️
superset/connectors/sqla/models.py	77.08% <100%> (-0.21%)	⬇️
superset/dataframe.py	97.7% <0%> (-1.05%)	⬇️
superset/viz.py	79.1% <0%> (-0.53%)	⬇️
superset/utils.py	88.07% <0%> (+0.02%)	⬆️

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[mistercrunch]

If a chart has been saved with a string say 5 seconds as a value, did you confirm that this load up ok in here as a "free form" value? From my understanding it should.

[mistercrunch]

@betodealmeida ^ please confirm and I'll merge

[betodealmeida]

It does, it loads with the saved value as freeform:

[nathan-quinn]

@betodealmeida @mistercrunch

I exported a postgres backed set of charts and dashboards to another postgres instance with this change included. It seems to work when viewing the actual chart, but when a time grain is persisted on a chart used in a dashboard I'm getting an error as such:

Traceback (most recent call last):
  File "/home/superset/superset/viz.py", line 362, in get_df_payload
    df = self.get_df(query_obj)
  File "/home/superset/superset/viz.py", line 160, in get_df
    self.results = self.datasource.query(query_obj)
  File "/home/superset/superset/connectors/sqla/models.py", line 705, in query
    sql = self.get_query_str(query_obj)
  File "/home/superset/superset/connectors/sqla/models.py", line 419, in get_query_str
    qry = self.get_sqla_query(**query_obj)
  File "/home/superset/superset/connectors/sqla/models.py", line 545, in get_sqla_query
    timestamp = dttm_col.get_timestamp_expression(time_grain)
  File "/home/superset/superset/connectors/sqla/models.py", line 134, in get_timestamp_expression
    expr = grain.function.format(col=expr)
AttributeError: 'str' object has no attribute 'function'

I was able to backfill values stored on slices.params.time_grain_sqla, to the ISO durations from here and this resolved the issue. Did I miss a migration someplace or should one be added for this?

[xrmx]

@nathanQuinn ~~i think the ".function" part should be removed~~~. It's the default of the get that is wrong, it shouldn't be a string but a Grain. And we are probably missing some tests :)

[mistercrunch]

@betodealmeida ^

[john-bodley]

@betodealmeida should there be a DB migration associated with this PR to update slices which reference the deprecated time grains?

cc: @michellethomas