fix: remove unneeded complexity in migration

[betodealmeida]

SUMMARY

The migration from SIP-68 was calling create_engine just to get the dialect associated with a given database. This required reimplementing many methods in the custom Database class defined in the migration, since it requires doing user impersonation, mutating the connection string, and much more. This was failing for BigQuery because it was not finding the credentials:

google.auth.exceptions.DefaultCredentialsError: Could not automatically determine credentials. Please set GOOGLE_APPLICATION_CREDENTIALS or explicitly create credentials and re-run the application. For more information, please see https://cloud.google.com/docs/authentication/getting-started

Turns out there's a simpler way of getting the dialect associated with a database that doesn't require create_engine. I implemented it in this PR.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

N/A

TESTING INSTRUCTIONS

Migration should run fine. I ran a downgrade and upgrade and it works fine, but I only testes with Postgres.

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

[codecov]

Codecov Report

Merging #19022 (9bb1470) into master (77063cc) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #19022   +/-   ##
=======================================
  Coverage   66.56%   66.56%           
=======================================
  Files        1641     1641           
  Lines       63495    63495           
  Branches     6425     6425           
=======================================
  Hits        42265    42265           
  Misses      19550    19550           
  Partials     1680     1680           

Flag	Coverage Δ
hive	52.59% <ø> (ø)
mysql	81.81% <ø> (ø)
postgres	81.86% <ø> (ø)
presto	52.44% <ø> (ø)
python	82.29% <ø> (ø)
sqlite	81.55% <ø> (ø)

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[eschutho]

wow.. that's a lot less code. :)

[betodealmeida]

wow.. that's a lot less code. :)

Yeah! The original implementation was copied from the current Database model, but of course there we use get_sqla_engine for other things than just accessing the dialect. I should've realized it could've been done in a simpler way.

[sadpandajoe]

🏷️ preset:2022.9