feat(comapct): Implement AppendCompactCoordinator for append-only unaware-bucket table compaction

[lxy-9602]

Purpose

Linked issue: #93

Implement AppendCompactCoordinator for synchronous compaction of append-only unaware-bucket tables (bucket=-1).

Key components:

• AppendCompactCoordinator: Entry point with static Run method. Loads schema, validates table type, scans small files, generates compact tasks via bin-packing (FileBin), and executes them synchronously.
• AppendCompactTask: Represents a single compaction task for a partition's file group. Reads source files and rewrites them into a single compacted file via AppendOnlyFileStoreWrite.
• FileBin + PackFiles: Bin-packing algorithm that sorts files by size ascending, then flushes a bin when EnoughContent (totalFileSize >= targetFileSize * 2) or EnoughInputFiles (count >= minFileNum).

TODO: DV (deletion vectors) is not yet supported in UNAWARE_BUCKET mode.

Tests

AppendCompactCoordinatorTest

API and Format

Add AppendCompactCoordinator ::Run()

Documentation

Generative AI tooling

Generated-by: Claude-4.6-Opus

[Copilot]

Pull request overview

Implements a new synchronous compaction entry point for append-only tables in UNAWARE_BUCKET mode (bucket = -1), scanning the latest snapshot for small files and rewriting them into compacted outputs.

Changes:

• Added AppendCompactCoordinator::Run() public API to scan small files, bin-pack them into tasks, and synchronously execute compaction rewrites.
• Introduced AppendCompactTask to perform the rewrite via AppendOnlyFileStoreWrite::CompactRewrite() and emit CommitMessage/CompactIncrement.
• Added comprehensive unit tests for coordinator behavior (partition filtering, validation failures, external paths, size thresholds, schema evolution).

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/paimon/core/operation/append_only_file_store_write.h	Exposes CompactRewrite as a public method for coordinator/task usage.
include/paimon/append/append_compact_coordinator.h	Adds new public API for append-only unaware-bucket compaction.
src/paimon/core/append/append_compact_coordinator.cpp	Implements snapshot scan, bin-packing, task generation, and synchronous execution.
src/paimon/core/append/append_compact_task.{h,cpp}	Defines/executes a single compaction rewrite task and builds commit messages.
src/paimon/core/append/append_compact_coordinator_test.cpp	Adds UT coverage for coordinator end-to-end scenarios and validations.
src/paimon/CMakeLists.txt	Wires new sources and test into the build.

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[lucasfang]

+1