docs: add native Windows MSVC build guide (no Docker / no WSL2)

[grimmjoww]

TL;DR

Decided to fuck around and find out — vchord builds natively on Windows MSVC. No Docker, no WSL2. This PR is documentation only; the codebase already supports x86_64-pc-windows-msvc as a target in xtask, just nobody had written the toolchain doc yet.

Result

Built a working vchord.dll on Windows 11 with:

• Visual Studio 2022 Community (MSVC)
• LLVM 22.1.4 (clang + libclang for pgrx-pg-sys bindgen)
• Rust 1.95.0 stable
• cargo-pgrx 0.17.0 (matching the pgrx pin)
• PostgreSQL 17.9 (EnterpriseDB installer)

Output: vchord.dll 9.4 MB PE32+ x64. dumpbin /dependents shows imports against postgres.exe, KERNEL32, ntdll, VCRUNTIME140, UCRT — exactly the same shape as pgvector's Windows DLL.

What changed

• docs/WINDOWS.md — new file with full toolchain + build + install + verification steps, and a "Pitfalls" section documenting the things that bit me
• README.md — one line under Quick Start pointing Windows users at the new doc

No source-code changes needed at all. The build "just worked" once the toolchain was set up.

The one gotcha worth highlighting

Rust 1.93 and 1.94 fail to build with E0658: use of unstable library feature 'stdarch_x86_avx512_f16' in crates/simd/src/floating_f16.rs:2014+. Those AVX-512 FP16 intrinsics (_mm512_fmadd_ph, _mm512_castsi512_ph, etc.) were stabilized in Rust 1.95.0 (April 2026). After rustup update, the build is clean — zero warnings, zero errors.

Worth noting in case anyone else hits this on slightly-older nightly/stable channels. The Linux CI didn't catch it because their rustup update step pulls latest stable.

Suggested follow-up (separate PR if you want it)

Add a Windows runner to .github/workflows/release.yml so users get a prebuilt vchord-pg17-x86_64-windows-msvc.zip artifact alongside the existing Linux .deb / .zip. Happy to draft that if there's interest.

Test plan

• cargo run -p xtask --release -- build produces build\pkglibdir\vchord.dll + extension SQL + control file
• dumpbin /dependents vchord.dll shows clean Windows dependency graph
• Zero warnings, zero errors at release profile
• CI green on this PR (docs only — should be trivial)

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Vibe-coded. 0% code from me, all from Claude. Co-author credit on the commit because I wanted it. We're shipping unlimited embeddings/vectors energy. 🚀

Closes the gap on Windows-native builds without changing your build system at all — just documenting what already works.

[github-actions]

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[grimmjoww]

Closing this PR.

After reading the CLA, the clauses granting TensorChord an irrevocable, transferable, sublicensable license — explicitly including the right to relicense contributions under "commercial, or proprietary license" and to "change or modify the license... from time to time" — go further than I'm comfortable with as a default for my contributions. I keep my work open and don't want to set a precedent of granting anyone the perpetual right to relicense it as proprietary later. That's a personal stance about how I license my own work, not a knock on vchord — the build itself was great and just worked once the toolchain was in place.

The Windows build documentation and helper scripts remain available at https://github.com/grimmjoww/vchord-windows-port under MIT for the community.

If anyone at TensorChord wants to incorporate the content into the official repo, please feel free to rewrite under your CLA — it documents an existing build path you already support, not novel IP. Happy to answer questions or clarify any of the build steps.

Thanks for vchord. The Windows-native build genuinely works; just sharing the toolchain notes openly without the CLA gate.

[usamoi]

It's already documented in Installation that x86_64 Windows is supported and tested. Source lists the environment requirements of building from source and installation steps.

The Linux CI didn't catch it because their rustup update step pulls latest stable.

It's expected. We will raise the required Rust version with each new release. The main branch always requires latest stable Rust.

Add a Windows runner to .github/workflows/release.yml so users get a prebuilt vchord-pg17-x86_64-windows-msvc.zip artifact

We don't build precompiled binaries unless strictly necessary. Mismatches between the ABIs of a precompiled VectorChord and the user's PostgreSQL can lead to critical failures. We only provide precompiled PostgreSQL packages for Debian/Linux that depend on the pgdg repository, rather than generic linux-gnu binaries, specifically because we have no way of knowing how users on other systems obtain their PostgreSQL installation.