Introduce PartitionGetter and Partition utils

[leekeiabstraction]

Purpose

Linked issue: close #209

Brief change log

• Added PartitionGetter
• Added Partition utils
• PartitionNameConverter logics are rolled into Partition utils as they are not used by any other component
• Added validation functions in TablePath

Tests

• Added test cases that mirror Java side

[leekeiabstraction]

@luoyuxia @fresh-borzoni Appreciate your reviews here

[Copilot]

Pull request overview

This PR introduces partition-related utilities for the Fluss Rust client, mirroring functionality from the Java implementation. It adds partition validation, auto-partition generation, and partition value conversion capabilities.

Changes:

• Added PartitionGetter for extracting partition names/specs from rows
• Added partition utilities including validation and auto-partition time generation
• Added validation functions to TablePath for name and prefix checking
• Added new InvalidPartition error variant

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
crates/fluss/src/util/partition.rs	New file containing partition validation, auto-partition generation, and datum-to-string conversion utilities
crates/fluss/src/util/mod.rs	Exports the new partition module
crates/fluss/src/metadata/table.rs	Adds validation methods for table/partition names and prefixes
crates/fluss/src/error.rs	Adds InvalidPartition error variant for partition-related errors
crates/fluss/src/client/table/partition_getter.rs	Implements PartitionGetter to extract partition information from rows, with comprehensive test coverage

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[leekeiabstraction]

Copilot comments have been addressed

[fresh-borzoni]

@leekeiabstraction Thank you for the PR.
Left comments. PTAL

[leekeiabstraction]

@fresh-borzoni Thank you for great catches. I've updated the PR accordingly. PTAL!

[luoyuxia]

@leekeiabstraction Thanks for the pr. Left some comments. PTAL

[leekeiabstraction]

@luoyuxia @fresh-borzoni Thank you for your reviews. Addressed/answered comments. PTAL!

[fresh-borzoni]

@leekeiabstraction Thanks for the PR. LGTM
Left comment for the discussion.

[fresh-borzoni]

nit: technically we can format into buffer directly:

use std::fmt::Write;

fn hex_string(bytes: &[u8]) -> String {
    let mut hex = String::with_capacity(bytes.len() * 2);
    for &b in bytes {
        write!(&mut hex, "{:02x}", b).unwrap();
    }
    hex
}

it would avoid allocation this way

[fresh-borzoni]

I wonder if Arc[String] is better, so cloning only Arc, as this code is hot, here it still makes sense.
I mean this later feels heavy:

ResolvedPartitionSpec::new(self.partition_keys.clone(), ...)

Though it would require changes in other places.

Perhaps it's better to handle in separate PR if we consider this worth it. WDYT?
cc @luoyuxia as well.

[luoyuxia]

Agree. I think we can consider in another pr.