[morristai]

Which issue does this PR close?

• Closes Allow downcasting ParquetFileReaderFactory like FileSource and DataSource #26633.

Rationale for this change

There is no way to tell which reader factory a ParquetSource uses. parquet_file_reader_factory() returns &Arc<dyn ParquetFileReaderFactory>, and the trait has no downcast path.

What changes are included in this PR?

ParquetFileReaderFactory gets Any as a supertrait, and dyn ParquetFileReaderFactory gets is and downcast_ref, like dyn FileSource in #21576. I also added a 56.0.0 upgrade guide entry, like the ones for MemoryPool (#21803) and QueryPlanner (#22241).

What is the testing strategy for this PR?

A unit test in source.rs sets each built-in factory on a ParquetSource and checks that parquet_file_reader_factory() downcasts to it.

Are there any user-facing changes?

Two new methods on dyn ParquetFileReaderFactory. The semver check will flag the new supertrait, but the trait already required 'static, so existing implementations compile unchanged.

Drafted with Claude. I reviewed the change and this text.

🤖 Generated with Claude Code

[github-actions]

Thank you for opening this pull request!

Reviewer note: cargo-semver-checks reported the current version number is not SemVer-compatible with the changes in this pull request (compared against the base branch).

Details

     Cloning apache/main
    Building datafusion-datasource-parquet v55.1.0 (current)
       Built [  40.268s] (current)
     Parsing datafusion-datasource-parquet v55.1.0 (current)
      Parsed [   0.027s] (current)
    Building datafusion-datasource-parquet v55.1.0 (baseline)
       Built [  41.001s] (baseline)
     Parsing datafusion-datasource-parquet v55.1.0 (baseline)
      Parsed [   0.029s] (baseline)
    Checking datafusion-datasource-parquet v55.1.0 -> v55.1.0 (no change; assume patch)
     Checked [   0.212s] 229 checks: 228 pass, 1 fail, 0 warn, 31 skip

--- failure trait_added_supertrait: non-sealed trait added new supertraits ---

Description:
A non-sealed trait added one or more supertraits, which breaks downstream implementations of the trait
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#generic-bounds-tighten
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.51.0/src/lints/trait_added_supertrait.ron

Failed in:
  trait datafusion_datasource_parquet::ParquetFileReaderFactory gained Any in file /home/runner/work/datafusion/datafusion/datafusion/datasource-parquet/src/reader.rs:71

     Summary semver requires new major version: 1 major and 0 minor checks failed
    Finished [  83.427s] datafusion-datasource-parquet