GH-50891: [C++][Parquet] DON'T MERGE NOW: Support FILE logical type

[HuaHuaY]

Rationale for this change

Implement apache/parquet-format#585

The Parquet format supporting the FILE type has not yet been released, so the corresponding functionality cannot currently be merged into the Arrow repository.

Since Arrow lacks specifications related to the FILE type, an Arrow extension type was defined to enable read-write round-trips for it.

What changes are included in this PR?

1. update parquet.thrift and the generated code
2. implement the Parquet FILE logical type

I will split this PR into two after the new Parquet release is published.

Are these changes tested?

Yes.

Are there any user-facing changes?

1. Add a new logical type at cpp/src/parquet/types.h.
2. Add a temporary extension type at cpp/src/arrow/extension/parquet_file.h and we can replace it at any time.

• GitHub Issue: [C++][Parquet] Introduce FileType reference implementation #50891

[github-actions]

Thanks for opening a pull request!

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After updating the title, you can mark the pull request as ready for review.

See also:

• Other pull requests
• Contribution Guidelines - Contributing Overview

[github-actions]

⚠️ GitHub issue #50891has been automatically assigned in GitHub to PR creator.

[HuaHuaY]

cc @brkyvz

[Copilot]

🟡 Changes recommended

There are release-build UB/crash risks in the new FILE extension restoration path due to unchecked checked_cast assumptions and potential null dereferences.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR introduces support for Parquet’s FILE logical type in the C++ Parquet implementation and adds a temporary Arrow extension type (parquet.file.experimental.v1) to enable read/write round-trips while Arrow lacks a native spec-level type for FILE.

Changes:

• Add FILE as a Parquet logical type (LogicalType::File() / FileLogicalType) with thrift serialization support.
• Implement Arrow<->Parquet schema conversion for FILE via a new Arrow extension type and ensure column-pruning behavior returns a struct when only part of the storage is read.
• Update parquet.thrift and regenerated thrift outputs; add unit tests covering schema conversion and read/write round-trips.

File summaries

File	Description
cpp/src/parquet/types.h	Adds FILE logical type API and FileLogicalType declaration.
cpp/src/parquet/types.cc	Implements FILE logical type behavior, thrift conversion, and nesting classification.
cpp/src/parquet/schema_test.cc	Extends logical type tests for FILE creation/properties/roundtrip.
cpp/src/parquet/parquet.thrift	Adds FileType to LogicalType union (and other upstream thrift updates).
cpp/src/parquet/arrow/schema.cc	Adds Arrow extension mapping to/from Parquet FILE; metadata restoration tweaks.
cpp/src/parquet/arrow/reader.cc	Allows pruned reads of FILE storage to return struct instead of failing extension creation.
cpp/src/parquet/arrow/arrow_schema_test.cc	Adds schema conversion tests for FILE extension and fallback behavior.
cpp/src/parquet/arrow/arrow_reader_writer_test.cc	Adds end-to-end read/write roundtrip + pruning behavior test for FILE.
cpp/src/generated/parquet_types.tcc	Regenerated thrift (adds FileType, Int96TimestampOrder, etc.).
cpp/src/generated/parquet_types.h	Regenerated thrift headers (new structs/enums and union members).
cpp/src/generated/parquet_types.cpp	Regenerated thrift sources (new struct implementations, enum maps).
cpp/src/arrow/meson.build	Adds extension/parquet_file.cc to Arrow C++ build.
cpp/src/arrow/extension/parquet_file.h	New FileExtensionType public header and extension name constant.
cpp/src/arrow/extension/parquet_file.cc	Implements FileExtensionType validation/serialization/array construction.
cpp/src/arrow/extension/parquet_file_test.cc	Adds validation tests for unsupported storage schemas.
cpp/src/arrow/extension/meson.build	Adds Meson test target and installs new header.
cpp/src/arrow/extension/CMakeLists.txt	Adds CMake test target for the new extension tests.
cpp/src/arrow/CMakeLists.txt	Adds extension/parquet_file.cc to Arrow library sources.

Review details

Suppressed comments (1)

cpp/src/parquet/arrow/schema.cc:1203

• FileStorageTypesCompatible assumes both inputs are struct types and uses checked_cast<const StructType&>(*inferred_type) without checking id(). In release builds checked_cast is a static_cast, so a non-struct type here is UB. Also, compatibility currently checks only field names/count, not the corresponding field types/nullability, which can lead to attempting to restore the FILE extension onto an incompatible inferred storage type.

bool FileStorageTypesCompatible(const std::shared_ptr<::arrow::DataType>& origin_type,
const std::shared_ptr<::arrow::DataType>& inferred_type) {
if (origin_type->num_fields() != inferred_type->num_fields()) {
return false;
}
const auto& inferred_struct_type =
checked_cast<const ::arrow::StructType&>(*inferred_type);
for (const auto& origin_field : origin_type->fields()) {
if (inferred_struct_type.GetFieldByName(origin_field->name()) == nullptr) {

• Files reviewed: 15/18 changed files
• Comments generated: 1
• Review effort level: Lite

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[dtenedor]

Thanks for working on this!

[dtenedor]

Here, any FILE-annotated group whose fields don't match the recognized set makes the entire read fail (Status::Invalid) rather than falling back to a plain struct.

Should we consider attempting Deserialize and keeping the plain struct_type on error? This would mirror variant's current behavior.

[HuaHuaY]

Sorry, I didn't quite catch what you meant. As I understand it, variant would return Status::Invalid in VariantExtensionType::Make, causing an error here as well.

My reasoning here is that if a type is FILE-annotated and was written by us, we guarantee its correctness. If it was written by another writer, then it should be attributed to that writer's implementation. If we were to allow arbitrary types to pass through, other code in the repository might encounter unknown errors when processing this data.

[dtenedor]

GetFieldByName returns nullptr if the name is missing or ambiguous. Should we DCHECK(origin_child != nullptr) (or return Status::Invalid)?

[HuaHuaY]

I am fine to add DCHECK(origin_child != nullptr).

[dtenedor]

The accepted storage types are broader than what's tested: IsSupportedField allows large_utf8/utf8_view and large_binary/binary_view, but round-trip tests only use utf8/int64/binary. Should we add at least one view/large variant round-trip?

[dtenedor]

Other test ideas:

• an unknown extra field alongside the valid ones
• a REQUIRED field among otherwise-valid ones
• wrong types for content_type/checksum/size (only uri/offset/inline type-errors are tested)

[dtenedor]

Is it intended to bring this in as well in this PR?

[HuaHuaY]

No. Since the Parquet version containing the FILE type has not yet been released, I don't know whether it's appropriate to update parquet.thrift in the Arrow repository prematurely. So this PR currently incorporates the contents of two separate PRs.

1. update parquet.thrift and the generated code
2. implement the Parquet FILE logical type

Code related to ALP is included in the first part. I will split this PR into two after the new Parquet release is published.