Closes core#115 partial. Schema-only change; the apply-endpoint filter
logic that reads this column lands with core#123 (drift detector +
queue + apply endpoint, the deferred follow-up of core#113).
Default 'production' so existing customers (Reno-Stars + any future
tenant) are default-safe. Synthetic dogfooding workspaces opt INTO
'canary' explicitly.
CHECK constraint pins the closed value set ('canary' | 'production') —
the apply endpoint's filter relies on the database to reject anything
else, so a future operator typo in PATCH /workspaces/:id ({update_tier:
'canery'}) returns a constraint violation, not silent fan-out to
nobody.
Partial index on canary rows since the apply-endpoint query path
('apply this update only to canary tier first') hits canary much more
often than production, and the production set is the much larger
default.
WHAT THIS DOES NOT DO (lands with core#123)
- PATCH endpoint to flip a workspace to canary
- The apply endpoint that consults the column
- Tests that exercise canary-vs-production fan-out
Schema-only foundation; same pattern as core#113 (workspace_plugins).
PHASE 4 SELF-REVIEW
Correctness: No finding — IF NOT EXISTS guards, DEFAULT clause means
existing rows get 'production' on migration apply.
Readability: No finding — comment block documents the tier semantics
+ the deferral to core#123.
Architecture: No finding — additive ALTER, partial index for the
expected access pattern.
Security: No finding — no code path; column constraint reduces blast
radius of bad PATCH input.
Performance: No finding — partial index minimizes write amplification
on the production-default rows.
REFS
core#115 — this issue
core#123 — apply endpoint follow-up (will exercise this column)
core#113 — version subscription DB foundation (sibling pattern)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
