feat(db_engine_specs): Add quirks to support Ascend.io/HiveServer2 with Impala driver.

[danielewood]

SUMMARY

This adds the quirks of Ascend.io's database to be handled using the Impala driver.

Note: I'm unsure if this approach for adding the db_engine_specs is the desired method, so I welcome feedback for needed changes.

Edit: I have modified the PR as my proposed changes for modifying get_table_names has been accepted in the latest Impala driver upstream, so there is no need for that when using impyla>=0.17a8 (should be released shortly).

Changes:

1. Adds ascend:// db_engine_spec that uses the Impala/Impyla driver
2. Use the default postgres time grain expressions to make charts work
3. Updated docs.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TEST PLAN

ADDITIONAL INFORMATION

• Has associated issue:
• 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

Merging #14682 (1a3a4c5) into master (568061e) will increase coverage by 0.09%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master   #14682      +/-   ##
==========================================
+ Coverage   77.46%   77.56%   +0.09%     
==========================================
  Files         959      960       +1     
  Lines       48465    48527      +62     
  Branches     5678     5678              
==========================================
+ Hits        37545    37638      +93     
+ Misses      10720    10689      -31     
  Partials      200      200              

Flag	Coverage Δ
hive	81.12% <100.00%> (+0.15%)	⬆️
mysql	81.39% <100.00%> (+0.15%)	⬆️
postgres	81.41% <100.00%> (+0.15%)	⬆️
presto	81.12% <100.00%> (+0.16%)	⬆️
python	81.95% <100.00%> (+0.16%)	⬆️
sqlite	81.04% <100.00%> (+0.15%)	⬆️

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

Impacted Files	Coverage Δ
superset/db_engine_specs/ascend.py	100.00% <100.00%> (ø)
superset/connectors/base/models.py	88.03% <0.00%> (-2.66%)	⬇️
superset/reports/logs/api.py	94.11% <0.00%> (-1.34%)	⬇️
superset/exceptions.py	98.70% <0.00%> (-1.30%)	⬇️
superset/connectors/sqla/models.py	90.14% <0.00%> (-0.13%)	⬇️
superset/views/core.py	75.48% <0.00%> (-0.04%)	⬇️
superset/utils/urls.py	100.00% <0.00%> (ø)
superset/databases/api.py	92.41% <0.00%> (ø)
superset/views/dynamic_plugins.py	100.00% <0.00%> (ø)
superset/databases/commands/create.py	92.15% <0.00%> (ø)
... and 13 more

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[danielewood]

A review would be appreciated.

[betodealmeida]

Looks great, sorry for missing this!