fix(python): Avoid loading all columns in read_parquet when columns parameter is specified

[itamarst]

Fixes #15098

Without optimizations, all columns would be loaded regardless of the columns argument, leading to higher CPU and memory usage.

[itamarst]

If you think a test to catch future regressions would be helpful, should be able to do so with pytest-memray.

[stinodego]

Thanks for noticing this one. That's a painful miss 😓

I'd be interested in a way to catch these types of bugs if we can do so without overly bloating the CI.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.26%. Comparing base (474ac34) to head (bd8ef13).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15229      +/-   ##
==========================================
- Coverage   81.26%   81.26%   -0.01%     
==========================================
  Files        1355     1355              
  Lines      175676   175676              
  Branches     2518     2518              
==========================================
- Hits       142761   142755       -6     
- Misses      32434    32439       +5     
- Partials      481      482       +1     

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[itamarst]

Given the impact of this (and the minor nature of the semantic change), I'd suggest you merge this without tests and I'll see about the testing in a separate issue. The tests would presumably want to cover a larger set of code anyway.