MSRV check and policy documentation

.github/workflows/ci.yml

@@ -290,6 +290,27 @@ jobs:
           enable-sccache: "true"
       - run: cargo minimal-versions check --direct --workspace --ignore-private
 
+  rust-msrv:
+    name: "Rust (MSRV)"
+    timeout-minutes: 30
+    runs-on: >-
+      ${{ github.repository == 'vortex-data/vortex'
+          && format('runs-on={0}/runner=amd64-medium/image=ubuntu24-full-x64-pre-v2/extras=s3-cache/tag=rust-msrv', github.run_id)
+          || 'ubuntu-latest' }}
+    env:
+      RUSTFLAGS: "-A warnings"
+    steps:
+      - uses: runs-on/action@v2
+        if: github.repository == 'vortex-data/vortex'
+        with:
+          sccache: s3
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7
+      - uses: ./.github/actions/setup-prebuild
+        with:
+          enable-sccache: "true"
+      - name: Check publishable crates against the MSRV
+        run: cargo hack --rust-version --no-dev-deps --ignore-private check --profile ci --all-features
+
   rust-lint:
     name: "Rust (lint)"
     needs: duckdb-ready

CONTRIBUTING.md

@@ -43,6 +43,20 @@ repository root, create or update the development environment with:
 uv sync --all-packages
 ```
 
+### Rust toolchain and MSRV
+
+Workspace declares a Minimum Supported Rust Version through `rust-version`
+in the root `Cargo.toml`, which the `Rust (MSRV)` CI job verifies by building
+the publishable crates with exactly that toolchain:
+
+```bash
+cargo hack --rust-version --no-dev-deps --ignore-private check --all-features
+```
+
+Read the [Rust version compatibility policy](README.md#rust-version-compatibility-policy) before
+changing `rust-version`; when the MSRV job fails, the usual fix is in the code or the dependency
+update, not the MSRV.
+
 ### Python bindings
 
 `vortex-data` is a mixed Python and Rust package. `uv` manages its Python environment, and

Cargo.toml

@@ -72,7 +72,7 @@ members = [
     "vortex-spatial",
 ]
 exclude = ["java/testfiles", "wasm-test"]
-resolver = "2"
+resolver = "3"
 
 [workspace.package]
 authors = ["Vortex Authors <hello@vortex.dev>"]

README.md

@@ -126,6 +126,10 @@ uv sync --all-packages
 See the [development workflows](CONTRIBUTING.md#development-workflows) for Python binding and
 documentation development, including Maturin rebuilds, targeted tests, and documentation checks.
 
+`rust-toolchain.toml` pins the toolchain used for development and CI, and is kept on the latest
+stable release. Building Vortex as a dependency only requires a toolchain that satisfies the
+[Rust version compatibility policy](#rust-version-compatibility-policy).
+
 ### Benchmarking
 
 Use `vx-bench` to run benchmarks comparing engines (DataFusion, DuckDB) and formats (Parquet, Vortex):
@@ -154,6 +158,38 @@ static GLOBAL_ALLOC: MiMalloc = MiMalloc;
 
 ## Project Information
 
+### Rust Version Compatibility Policy
+
+**The policy: Vortex supports the four most recent stable minor releases.** Writing the latest
+stable release as `1.N`, that means `1.N`, `1.N-1`, `1.N-2`, and `1.N-3` all build Vortex, so the
+three minor releases older than the latest stable release. Only the minor version is constrained;
+Minimum Supported Rust Version (MSRV) declared in `Cargo.toml` must be **no newer than `1.N-3`**,
+patch releases are never a factor.
+
+An MSRV *older* than `1.N-3` is always acceptable — supporting extra releases cannot break the
+guarantee. An MSRV *newer* than `1.N-3` does not meet the policy. For example, once `1.98` is the
+latest stable release:
+
+| Declared MSRV | Status |
+| --- | --- |
+| `1.94` or older | Acceptable — supports more releases than required |
+| `1.95` | Exactly on policy |
+| `1.96` or newer | Does not meet the policy |
+
+The MSRV is raised in occasional deliberate steps rather than on every Rust release, so it drifts
+relative to that bound.
+
+How the policy is applied:
+
+- The MSRV is declared once, as `rust-version` in the root `Cargo.toml`, and inherited by every
+  crate in the workspace. That value, not this document, is the source of truth.
+- The toolchain pinned in `rust-toolchain.toml` tracks the latest stable release and is independent
+  of the MSRV. It is what contributors and most CI jobs build with.
+- CI enforces the declared MSRV in the `Rust (MSRV)` job, which builds the publishable crates with
+  exactly that toolchain. When it fails, the first choices are to express the code without the
+  newer Rust feature, or to hold back the dependency update that raised the requirement. Raising
+  `rust-version` is a last resort.
+
 ### License
 
 Licensed under the Apache License, Version 2.0.

rust-toolchain.toml

@@ -1,4 +1,4 @@
 [toolchain]
-channel = "1.95"
+channel = "1.97.1"
 components = ["rust-src", "rustfmt", "clippy", "rust-analyzer"]
 profile = "minimal"

vortex-array/src/expr/stats/bound.rs

@@ -139,9 +139,7 @@ impl<T: PartialOrd> PartialOrd<T> for LowerBound<T> {
     fn partial_cmp(&self, other: &T) -> Option<Ordering> {
         match &self.0 {
             Exact(lhs) => lhs.partial_cmp(other),
-            Inexact(lhs) => lhs
-                .partial_cmp(other)
-                .and_then(|o| if o == Ordering::Less { None } else { Some(o) }),
+            Inexact(lhs) => lhs.partial_cmp(other).filter(|&o| o != Ordering::Less),
             Absent => None,
         }
     }
@@ -241,13 +239,7 @@ impl<T: PartialOrd> PartialOrd<T> for UpperBound<T> {
     fn partial_cmp(&self, other: &T) -> Option<Ordering> {
         match &self.0 {
             Exact(lhs) => lhs.partial_cmp(other),
-            Inexact(lhs) => lhs.partial_cmp(other).and_then(|o| {
-                if o == Ordering::Greater {
-                    None
-                } else {
-                    Some(o)
-                }
-            }),
+            Inexact(lhs) => lhs.partial_cmp(other).filter(|&o| o != Ordering::Greater),
             Absent => None,
         }
     }

vortex-bench/src/tpcds/tpcds_benchmark.rs

@@ -39,7 +39,7 @@ impl TpcDsBenchmark {
                 Url::from_directory_path(&data_dir_with_sf).map_err(|_| {
                     anyhow!(
                         "Failed to create URL from directory path: {:?}",
-                        &data_dir_with_sf
+                        data_dir_with_sf
                     )
                 })
             }

vortex-bench/src/tpch/benchmark.rs

@@ -49,7 +49,7 @@ impl TpcHBenchmark {
                 Url::from_directory_path(&data_dir_with_sf).map_err(|_| {
                     anyhow::anyhow!(
                         "Failed to create URL from directory path: {:?}",
-                        &data_dir_with_sf
+                        data_dir_with_sf
                     )
                 })
             }

vortex-bench/src/utils/file.rs

@@ -130,7 +130,7 @@ pub fn resolve_data_url(remote_data_dir: Option<&str>, local_subdir: &str) -> Re
         None => {
             let data_dir = data_dir().join(local_subdir);
             Url::from_directory_path(&data_dir).map_err(|_| {
-                anyhow::anyhow!("Failed to create URL from directory path: {:?}", &data_dir)
+                anyhow::anyhow!("Failed to create URL from directory path: {:?}", data_dir)
             })
         }
         Some(remote_data_dir) => {

vortex-datafusion/src/v2/source.rs

@@ -362,7 +362,7 @@ impl fmt::Debug for VortexDataSource {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         f.debug_struct("VortexScanSource")
             .field("schema", &self.leftover_schema)
-            .field("projection", &format!("{}", &self.projected_projection))
+            .field("projection", &format!("{}", self.projected_projection))
             .field("filter", &self.filter.as_ref().map(|e| format!("{}", e)))
             .field("limit", &self.limit)
             .finish()

vortex-duckdb/src/table_function.rs

@@ -827,10 +827,11 @@ pub fn statistics(bind_data: &TableFunctionBind, column_index: usize) -> Option<
     let MultiLayoutChild::Opened { reader, .. } = &children[0] else {
         return None;
     };
-    let stats_sets = match reader.as_any().downcast_ref::<FileStatsLayoutReader>() {
-        Some(inner) => inner.file_stats().stats_sets(),
-        None => return None,
-    };
+    let stats_sets = reader
+        .as_any()
+        .downcast_ref::<FileStatsLayoutReader>()?
+        .file_stats()
+        .stats_sets();
     // Columns with pushed projection expression output expression results,
     // and not column values
     if bind_data.column_fields[column_index]

vortex-python/src/iter/python.rs

@@ -45,7 +45,7 @@ impl Iterator for PythonArrayIterator {
                         if array.dtype() != &self.dtype {
                             Err(PyTypeError::new_err(format!(
                                 "ArrayIterator dtype mismatch. Expected {:?}, got {:?}",
-                                &self.dtype,
+                                self.dtype,
                                 array.dtype()
                             )))
                         } else {

vortex-python/src/scalar/factory.rs

@@ -145,7 +145,7 @@ fn scalar_helper_inner(value: &Bound<'_, PyAny>, dtype: Option<&DType>) -> PyRes
             if names != dtype.names() {
                 return Err(PyValueError::new_err(format!(
                     "Dictionary field names {:?} do not match target dtype names {:?}",
-                    &names,
+                    names,
                     dtype.names()
                 )));
             }

vortex-web/crate/Cargo.toml

@@ -2,7 +2,7 @@
 name = "vortex-web-wasm"
 version = "0.1.0"
 edition = "2024"
-rust-version = "1.91.0"
+rust-version = { workspace = true }
 license = "Apache-2.0"
 description = "WASM bindings for the Vortex web explorer"
 publish = false