GH-49923: [Parquet][Python] Inconsistent default values for Parquet pre_buffer

[rok]

Rationale for this change

Default pre_buffer=True on parquet APIs should probably be made consistent.

What changes are included in this PR?

Couple of default parameter changes and an updated docstring.

Are these changes tested?

By CI.

Are there any user-facing changes?

Users will see changes to default behavior. It's hard to estimate how disruptive (if at all) this will be.

• GitHub Issue: [Parquet][Python] Inconsistent default values for Parquet pre_buffer #49923

[github-actions]

⚠️ GitHub issue #49923has been automatically assigned in GitHub to PR creator.

[pitrou]

+1, let's hope CI doesn't break

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 0 benchmarking runs that have been run so far on merge-commit 2a89d03.

None of the specified runs were found on the Conbench server.

The full Conbench report has more details.

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 3 benchmarking runs that have been run so far on merge-commit 2a89d03.

There was 1 benchmark result with an error:

• Commit Run on amd64-m5-4xlarge-linux at 2026-05-15 03:22:48Z
  • file-read (Python) with compression=uncompressed, dataset=nyctaxi_2010-01, file_type=feather, output_type=dataframe

There were 6 benchmark results indicating a performance regression:

• Commit Run on amd64-m5-4xlarge-linux at 2026-05-15 03:22:48Z
  • file-read (Python) with compression=uncompressed, dataset=nyctaxi_2010-01, file_type=feather, output_type=table
  • file-read (Python) with compression=uncompressed, dataset=nyctaxi_2010-01, file_type=feather, output_type=table
• and 4 more (see the report linked below)

The full Conbench report has more details. It also includes information about 1 possible false positive for unstable benchmarks that are known to sometimes produce them.

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 3 benchmarking runs that have been run so far on merge-commit 2a89d03.

There was 1 benchmark result with an error:

• Commit Run on amd64-m5-4xlarge-linux at 2026-05-15 03:22:48Z
  • file-read (Python) with compression=uncompressed, dataset=nyctaxi_2010-01, file_type=feather, output_type=dataframe

There were 6 benchmark results indicating a performance regression:

• Commit Run on amd64-m5-4xlarge-linux at 2026-05-15 03:22:48Z
  • file-read (Python) with compression=uncompressed, dataset=nyctaxi_2010-01, file_type=feather, output_type=table
  • file-read (Python) with compression=uncompressed, dataset=nyctaxi_2010-01, file_type=feather, output_type=table
• and 4 more (see the report linked below)

The full Conbench report has more details. It also includes information about 1 possible false positive for unstable benchmarks that are known to sometimes produce them.