Editing an existing share alias (e.g. slug `te` -> `ted`) failed to update
the displayed `/l/<alias>` link: `setAlias()` looked the requested slug up by
name and, if free, INSERTed a brand-new row, leaving the page with multiple
alias rows. The modal then read via `findByPageId().executeTakeFirst()` with no
`ORDER BY`, so Postgres returned an arbitrary (in practice the oldest, stale)
row. Every edit also spawned an orphan row that kept a live `/l/<old>` link
forever. Regression of #205.
Enforce the invariant "a page has EXACTLY ONE custom address":
- `setAlias()` now resolves the page's current alias row and RENAMES it in
place when the requested name is free (insert only when the page has none),
keeps the same-name no-op and the cross-page 409 `ALIAS_REASSIGN_REQUIRED`
+ confirmed-retarget flow, and after any successful write DELETEs all other
alias rows for the page (self-heal). Runs in one transaction so the page is
never transiently empty or duplicated.
- repo: add `updateAlias` (rename) and `deleteOthersForPage`; make
`findByPageId` deterministic with `ORDER BY created_at DESC, id DESC`.
- migration: dedup existing rows (keep newest per page) + a PARTIAL unique
index `(workspace_id, page_id) WHERE page_id IS NOT NULL` so dangling
aliases still coexist while live ones are one-per-page.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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