[prrao87]

Why

The Python test job spends 270 to 320 s in "Build Python extension", while the tests themselves take about 35 s with pytest -n auto. The build is slow because the job's rust-cache is stale and never refreshed.

rust-cache builds its key from the Cargo.toml of each member of the workspaces it's given (versions blanked) plus the crates.io packages in their Cargo.lock. The step only listed crates/lance-csr-python, which is excluded from the root workspace, so its key never included crates/lance-csr/Cargo.toml or crates/lance-csr-catalog/Cargo.toml, which the bindings use as path dependencies.

#109 added ipc_compression to arrow's features in crates/lance-csr/Cargo.toml. That added no crates.io packages, so the key v0-rust-lance-csr-python-Linux-x64-113ee5d7-125ac86f, saved on 2026-10-30, still matched exactly. rust-cache doesn't re-save an exact match, so every run since restores a cache built with the old features and recompiles arrow, DataFusion and Lance. The Rust jobs aren't affected: their workspace is the root one, so the feature change gave them a new key.

What

List both workspaces in the step:

workspaces: |
  . -> target
  crates/lance-csr-python -> target

The key now hashes the root members' manifests too, still with versions blanked, so release version bumps don't bust the cache. This job never builds the root workspace, so ./target doesn't exist; rust-cache's target cleanup on save and restore is wrapped in try/catch, and the cache save skips paths that don't exist.

Effect

This PR's run computes a new key but can't save it (save-if is main only), so its build is still cold. The speed-up shows from the second main run after merge: the first main run builds cold and saves the cache, later runs restore it.

Testing

• The Python test run on this PR reports a new rust-cache key instead of a full match on 113ee5d7-125ac86f.

🤖 Generated with Claude Code

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