Histograms broken with 0.32 due to new version of pydruid

[elukey]

After upgrading to 0.32 a histogram chart that worked on 0.31 doesn't render anymore due to a pydruid exception.

Expected results

The histogram chart correctly visualized.

Actual results

The following exception is thrown:

Traceback (most recent call last):
  File "/srv/deployment/analytics/superset/venv/lib/python3.7/site-packages/superset/viz.py", line 410, in get_df_payload
    df = self.get_df(query_obj)
  File "/srv/deployment/analytics/superset/venv/lib/python3.7/site-packages/superset/viz.py", line 213, in get_df
    self.results = self.datasource.query(query_obj)
  File "/srv/deployment/analytics/superset/venv/lib/python3.7/site-packages/superset/connectors/druid/models.py", line 1287, in query
    client=client, query_obj=query_obj, phase=2)
  File "/srv/deployment/analytics/superset/venv/lib/python3.7/site-packages/superset/connectors/druid/models.py", line 884, in get_query_str
    return self.run_query(client=client, phase=phase, **query_obj)
  File "/srv/deployment/analytics/superset/venv/lib/python3.7/site-packages/superset/connectors/druid/models.py", line 1123, in run_query
    client.scan(**qry)
  File "/srv/deployment/analytics/superset/venv/lib/python3.7/site-packages/pydruid/client.py", line 559, in scan
    query = self.query_builder.scan(kwargs)
  File "/srv/deployment/analytics/superset/venv/lib/python3.7/site-packages/pydruid/query.py", line 445, in scan
    self.validate_query(query_type, valid_parts, args)
  File "/srv/deployment/analytics/superset/venv/lib/python3.7/site-packages/pydruid/query.py", line 265, in validate_query
    .format(valid_parts))
ValueError: Query component: dimensions is not valid for query type: scan.The list of valid components is: 
 ['datasource', 'granularity', 'filter', 'columns', 'metrics', 'intervals', 'limit', 'context']

This is due to the following change in pydruid:

druid-io/pydruid@0a59a70

That got released in 0.5.2 (the version stated in 0.32's requirement.txt).

I have fixed it with the following code:

--- a/superset/connectors/druid/models.py
+++ b/superset/connectors/druid/models.py
@@ -1119,7 +1119,8 @@ class DruidDatasource(Model, BaseDatasource):
             columns.append('__time')
             del qry['post_aggregations']
             del qry['aggregations']
-            qry['dimensions'] = columns
+            del qry['dimensions']
+            qry['columns'] = columns
             qry['metrics'] = []
             qry['granularity'] = 'all'
             qry['limit'] = row_limit

Environment

(please complete the following information):

• superset version: 0.32rc2
• python version: 3.7

Checklist

Make sure these boxes are checked before submitting your issue - thank you!

• I have checked the superset logs for python stacktraces and included it here as text if there are any.
• I have reproduced the issue with at least the latest released version of superset.
• I have checked the issue tracker for the same issue and I haven't found one similar.

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[mistercrunch]

@elukey would you mind opening a PR?

[elukey]

@mistercrunch done!

[elukey]

PR is ready to review/merge if anybody has time! :)

[elukey]

PR merged, thanks!