Configurable RocksDB compression

[cb1kenobi]

Summary

Exposes RocksDB block/blob compression as a per-column-family option (issue #201).

• compression open option — an algorithm name ('lz4', 'zstd', 'zlib', 'none', …) or { algorithm, level }. Applies to both SST block compression and blob-file compression (large values ≥ 2 KB become blobs, whose compression otherwise defaults to none).
• Default: LZ4 (applied natively in Database::Open) when the build supports it, else RocksDB's own default. Confirmed & documented that RocksDB's stock default is Snappy; we override to LZ4.
• supportedCompression — module constant listing algorithms compiled into the build (from GetSupportedCompressions()). Opening with an unavailable algorithm throws.
• db.compression getter — reads the live value via DB::GetOptions.
• Native name↔enum mapping + supported list in the Node-free core/compression.{h,cpp} (GoogleTest-covered).

Build robustness (dynamic lib linking)

librocksdb.a references, but doesn't bundle, the compression libraries it was built with. binding.gyp now links exactly the compression static libs the resolved prebuild ships, enumerated at configure time by scripts/configure-rocksdb.mjs (which also provisions the pinned prebuild). This means the build works against both an older none+zlib prebuild and a compression-enabled one — no version-bump coupling. To actually activate LZ4, a compression-enabled prebuild must be pinned in package.json (currently 11.1.2); the feature is forward-compatible until then.

Where to look / open items for the reviewer

• Cold open applies the requested compression to every existing column family, not just the one being opened (DBDescriptor::open). This is intended per the author, but worth a look — it means opening a multi-CF DB with a compression option changes all CFs' algorithm for subsequently-written files. A second in-process open that explicitly requests a different algorithm for an already-open CF now throws (DBRegistry::OpenDB); a plain reopen inherits the live setting (DBOptions::compressionExplicit gates this).
• Block vs blob compression are unified (same algorithm for both). Splitting them (e.g. lz4 blocks + zstd blobs) was deliberately deferred (YAGNI); the object form extends cleanly later.
• scripts/configure-rocksdb.mjs runs init-rocksdb at gyp configure time (before the prepare-rocksdb build action) so the enumerated lib set matches what will link. The Windows path (spawn + AdditionalDependencies splice) is unverified locally — worth watching on CI.

Testing

• test/compression.test.ts — supported list, getter/defaults, validation, on-disk size comparison across multiple databases, already-open conflict cases, and a normalizeCompression guard suite.
• test/native/compression_test.cc — name↔type mapping + supported-list GoogleTests.
• benchmark/compression.bench.ts — RocksDB-only write/read throughput per available algorithm.

Notes

• Stacked on #734 (init-rocksdb prerelease/revision version) — based on that branch; retarget to main once Fix init-rocksdb skipping updates for pinned prerelease/revision versions #734 merges. The bottom three commits belong to Fix init-rocksdb skipping updates for pinned prerelease/revision versions #734.
• User-facing surface is documented in the repo README.md (this library's docs); no separate documentation-repo change needed.
• Generated by an LLM (Claude Opus 4.8). The code-review findings surfaced during development were addressed in the latest commit; the remaining open items are called out above.

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request introduces configurable block and blob compression (such as LZ4, Zstd, and Zlib) to rocksdb-js, including build-time library detection, native mapping logic, and public APIs to configure and query compression. The review feedback highlights several important issues: a missing optional flag when parsing the 'compression' option that would cause database opens to fail when omitted, an incorrect override of the default compression level to 0 when 'compressionLevel' is not specified, a typo in the Windows static library name (using 'zs.lib' instead of 'zlib.lib' or 'zlibstatic.lib'), and a recommendation to improve cross-platform script execution by spawning the Node executable with the tsx CLI entry point directly instead of relying on the shell wrapper on Windows.