Columns names outputs are inconsistents and case sensitive

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
55/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Quiet
Tech stack
pandas, python
Domain
data, database

Research direction

Start by running the supplied Python reproduction against the current DuckDB Python package and compare rel.pl(), rel.df(), the Arrow conversions, and the lazy result. Trace the Python relation-to-Polars and relation-to-pandas entry points, then add or update regression coverage so equivalent outputs handle the case-variant columns consistently.

Written by the indexing model from the issue text.

Description

needs triage
What happens?

Output of the code block:

PS C:\Users\tibo\python_codes\pql> uv run t.py
relation.columns: ['foo', 'Foo']
to_arrow_table: ['foo', 'Foo']
pl.from_arrow: ['foo', 'Foo']
relation.pl eager: ['foo', 'Foo_1']
relation.pl lazy: ['foo', 'Foo']
pandas result: ['foo', 'Foo_1']
arrow query result: ['foo', 'Foo']
PS C:\Users\tibo\python_codes\pql>

pandas and polars dataframe don't give the same results as the rest.

To Reproduce
import duckdb
import polars as pl

rel = duckdb.from_query("select 1 as foo, 2 as Foo")

print("relation.columns:", rel.columns)
print("to_arrow_table:", rel.to_arrow_table().column_names)
print("pl.from_arrow:", pl.from_arrow(rel.to_arrow_table()).columns)
print("relation.pl eager:", rel.pl().columns)
print("relation.pl lazy:", rel.pl(lazy=True).collect().columns)
print("pandas result:", list(rel.df().columns))
print("arrow query result:", rel.to_arrow_reader().read_all().column_names)
OS:

Windows

DuckDB Package Version:

1.5.1

Python Version:

3.13.7

Full Name:

Stettler Thibaud

Affiliation:

University of Geneva

What is the latest build you tested with? If possible, we recommend testing with the latest nightly build.

1.5.2.dev40

Did you include all relevant data sets for reproducing the issue?

Yes

Did you include all code required to reproduce the issue?
  • Yes, I have
Did you include all relevant configuration to reproduce the issue?
  • Yes, I have
Dominant language
Python
Stars
186
Forks
113
Avg merge
20h 58m
Merged PRs (30d)
11

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