fix(python): Fixes a read_database issue loading specific datetime types from SQL Server backends

[alexander-beedie]

Closes #11912.

Very slightly reworks cursor introspection/load for read_database, avoiding a SQL Server issue with DATETIMEOFFSET cols. Validated against a local SQL Server Docker image with a suitable test table...

(Also improves ODBC connection string detection as a trivial drive-by).

[stinodego]

Looks good to me - feel free to merge if CI is green.

If it's possible to test (part of) this locally, adding a test would be good.

[alexander-beedie]

If it's possible to test (part of) this locally, adding a test would be good.

Hmm, I might be able to mock something, but what we really need are some ephemeral DBs integrated into the CI pipeline¹ so we can do a better job covering read_database😅

(PostgreSQL and SQL Server have official Docker images; no doubt a few others do too).

Footnotes

1. Ref: https://github.com/pola-rs/polars/issues/12815 ↩

[stinodego]

I didn't really intend for you to set up a complicated mocking structure for this PR 😄 I was just thinking maybe extract part of the logic as a testable function. But it's up to you!

[alexander-beedie]

I didn't really intend for you to set up a complicated mocking structure for this PR 😄 I was just thinking maybe extract part of the logic as a testable function. But it's up to you!

Tricky... it needs a pretty specific interaction with the DB cursor to expose it; without mocking it would be hard to tease it out from inside ConnectionExecutor :(

I did find a related gremlin that's much easier to isolate though; will create a separate Issue for that shortly.

[codecov]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (b036459) 80.84% compared to head (cc61718) 80.83%.
Report is 3 commits behind head on main.

Files	Patch %	Lines
py-polars/polars/io/database.py	33.33%	5 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #14627      +/-   ##
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- Coverage   80.84%   80.83%   -0.01%     
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  Files        1326     1326              
  Lines      173065   173071       +6     
  Branches     2450     2453       +3     
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- Hits       139907   139903       -4     
- Misses      32684    32693       +9     
- Partials      474      475       +1     

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