cache: redesign as a Bazel-style CAS and action cache

[kyleconroy]

Redesigns sqlc's on-disk cache after Bazel's local disk cache: a content-addressable store keyed by SHA-256 plus an action cache, replacing the ad-hoc query analysis cache and WASM plugin cache.

Design

The cache root (SQLCCACHE, defaulting to the user cache dir) now holds:

• cas/<xx>/<hash> — content-addressable blobs keyed by the SHA-256 of their contents: plugin binaries, query analysis protos, compiled WASM machine code. Writes are atomic (temp + rename), reads re-hash and evict corrupt entries, and Put repairs corrupt entries in place, so concurrent sqlc processes race benignly.
• ac/<xx>/<hash> — action cache entries mapping the digest of a unit of work (a mnemonic plus length-prefix-framed inputs) to the CAS digests of its outputs. A hit is only reported if every referenced output still exists in the CAS, like Bazel's disk cache.
• exec/<action-hash>/ — materialized output trees for tools that read outputs from disk (wazero's compilation cache). Safe to delete; the authoritative bytes live in the CAS.

The sha256 of the sqlc binary itself is an implicit first input of every action, the way Bazel treats the toolchain as an action input: version strings under-invalidate (every dev build reports the same version), while the binary hash guarantees a rebuilt sqlc never reuses entries produced by different analysis or codegen logic. It also subsumes the embedded wazero version and GOOS/GOARCH as compile-action inputs.

All storage I/O is confined to the cache directory through an os.Root, so no entry name — hash-derived or deserialized from an action cache entry — can traverse outside it.

What uses it

• Query analysis (managed databases) is a QueryAnalysis action keyed by config + schema + query, with the analysis proto stored in the CAS. Replaces the FNV-64-keyed flat-file cache.
• WASM plugin fetches need no action cache entry at all: the sha256 declared in the config file is itself a content address, so the binary is stored and loaded directly from the CAS under that checksum — mirroring Bazel's repository cache — and the checksum is re-verified on every read. In-process fetch dedup via singleflight is unchanged.
• WASM compilation is a CompileModule action keyed by the module checksum (plus the implicit binary hash). wazero has no public API to serialize compiled modules, so on a miss it compiles into the action's exec/ dir and the resulting files are lifted into the CAS (PutTree); on a hit they're materialized back (GetTree) for wazero's file cache to load instead of recompiling. Replaces the previous long-lived wazero-managed directory.

Testing

• Full --tags=examples suite passes against live PostgreSQL and MySQL, including all WASM plugin end-to-end tests.
• Verified live with sqlc-gen-greeter: first run populates the cache, a fully offline run generates from cache alone, a tampered blob is detected, evicted, and re-fetched, and after deleting exec/ the machine code is rematerialized byte-identical from the CAS.
• Verified invalidation: two sqlc binaries differing only in an injected version string produce two distinct CompileModule action entries — which both point at the same deduplicated machine-code blob in the CAS, since the embedded wazero is identical.

🤖 Generated with Claude Code

https://claude.ai/code/session_01MPgq3rwip76D554BktbqR4