fix: make byte hashing independent of char signedness

[wgtmac]

Purpose

Fix ARM bucket mismatches caused by platform-dependent char signedness.

This change makes byte hashing explicit:

• Hive TINYINT hashing now treats row bytes as signed Java bytes.
• Hive string/binary byte-array hashing now treats high-bit bytes as signed Java bytes.
• Murmur tail-byte hashing now reads tail bytes as int8_t, avoiding unsigned plain-char drift.

Tests

Pass existing CI.

API and Format

N/A

Documentation

N/A

Generative AI tooling

Generated-by: OpenAI Codex

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR adjusts byte handling in hashing code paths to treat bytes as signed 8-bit values (consistent with Java/Hive semantics), improving hash compatibility across languages.

Changes:

• Update Hive hashing for raw bytes and TINYINT to use signed-byte interpretation.
• Update MurmurHash byte mixing and change GetByte to return int8_t.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/paimon/core/bucket/hive_hasher.h	Interprets char bytes as signed 8-bit when computing hash.
src/paimon/core/bucket/hive_bucket_function.cpp	Ensures TINYINT values are sign-extended before hashing.
src/paimon/common/utils/murmurhash_utils.h	Applies signed-byte mixing and changes GetByte return type to int8_t.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

[zjw1111]

Thanks for the fix! Could you add a compatibility test that compares the results with Java, covering negative tinyint values, high-byte UTF-8/binary data, and the Murmur unaligned tail-byte case?

[wgtmac]

Thanks for the fix! Could you add a compatibility test that compares the results with Java, covering negative tinyint values, high-byte UTF-8/binary data, and the Murmur unaligned tail-byte case?

I would love to do this. But unfortunately I cannot build and run the test on my macOS laptop and I do not yet have access to the Java code. What I tried is to make sure it does not break existing CI and work as expected on our internal ARM environment.

[zjw1111]

+1