feat: improve logic in is_select

[betodealmeida]

SUMMARY

sqlparse fails to identify this query as a SELECT:

WITH foo AS(
SELECT
  FLOOR(__time TO WEEK) AS "week",
  name,
  COUNT(DISTINCT user_id) AS "unique_users"
FROM "druid"."my_table"
GROUP BY 1,2
)
SELECT
  f.week,
  f.name,
  f.unique_users
FROM foo f

This happens because AS( (no space) is identified as a function, and because of that the statement has type "UKNOWN".

I improved the logic in is_select so that when the token is "UNKNOWN" we check for DDL and DML, returning true only if there's no DDL and the only DML is a SELECT.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

N/A

TESTING INSTRUCTIONS

I added unit tests covering the bug and a few more.

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

[mistercrunch]

LGTM

[codecov]

Codecov Report

Merging #17329 (ffce826) into master (7c6d6f4) will decrease coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master   #17329      +/-   ##
==========================================
- Coverage   77.15%   77.09%   -0.07%     
==========================================
  Files        1037     1037              
  Lines       55639    55647       +8     
  Branches     7612     7612              
==========================================
- Hits        42930    42902      -28     
- Misses      12459    12495      +36     
  Partials      250      250              

Flag	Coverage Δ
hive	81.55% <100.00%> (+<0.01%)	⬆️
mysql	81.98% <100.00%> (+<0.01%)	⬆️
postgres	81.99% <100.00%> (+<0.01%)	⬆️
presto	?
python	82.34% <100.00%> (-0.12%)	⬇️
sqlite	81.66% <100.00%> (?)

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

Impacted Files	Coverage Δ
superset/sql_parse.py	99.42% <100.00%> (+0.02%)	⬆️
superset/db_engine_specs/presto.py	84.30% <0.00%> (-6.07%)	⬇️
superset/connectors/sqla/models.py	85.99% <0.00%> (-1.41%)	⬇️
superset/models/core.py	89.26% <0.00%> (-0.74%)	⬇️
superset/utils/cache.py	74.52% <0.00%> (+0.94%)	⬆️
superset/result_set.py	98.38% <0.00%> (+1.61%)	⬆️
superset/utils/celery.py	89.65% <0.00%> (+3.44%)	⬆️
superset/connectors/sqla/utils.py	92.15% <0.00%> (+3.92%)	⬆️
superset/db_engine_specs/sqlite.py	97.29% <0.00%> (+5.40%)	⬆️

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