[GitHub] villebro opened a new pull request #6847: [WIP] Refactor dataframe and column name mutation logic

[GitBox <gi...@apache.org>]

villebro opened a new pull request #6847: [WIP] Refactor dataframe and column name mutation logic
URL: https://github.com/apache/incubator-superset/pull/6847
 
 
   Several small refactors, features and fixes related to SQLAlchemy engines:
   - Add flag to disable aliases in `db_engine_specs`. By default engines support aliases; this is only disabled on Pinot for now. If the engine doesn't support aliases, labels aren't added to columns (see screenshot below).
   - Move dataframe logic back to `connectors/sqla/models.py` from `db_engine_specs.py` and merge it with the column renaming logic from before.
   - Add `max_column_name_length` property to `db_engine_specs`, and default to MD5 hash if column name is exceeded. Add max lengths to engines that were easy to find by googling.
   - Fix a few linting errors in `db_engine_specs`.
   
   # Example
   
   When creating a chart on Pinot where `COUNT(*)` is calculated grouping by `playerID`, the result shows up like before:
   
   <img width="1262" alt="screenshot 2019-02-09 at 16 09 37" src="https://user-images.githubusercontent.com/33317356/52521935-a1e72d00-2c87-11e9-8461-2b6d6240a43f.png">
   
   Looking at the query, the alias is gone, making it regular PQL:
   
   <img width="897" alt="screenshot 2019-02-09 at 16 09 25" src="https://user-images.githubusercontent.com/33317356/52521966-01453d00-2c88-11e9-8708-6071ed861240.png">
   
   FYI @agrawaldevesh please check this and give comments when you have the time. I tested this with your fork of `pinot_dbapi` (I assume that's the one you are using for now).

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