Repairs phoenix_kit_* tables whose uuid column is the wrong type, nullable,
or not the primary key.
V163 performs this repair automatically during mix ecto.migrate, but skips
any table large enough that the rewrite's ACCESS EXCLUSIVE lock would be an
outage rather than a pause. This task is the deliberate, operator-chosen path
for those — run it in a maintenance window.
mix phoenix_kit.repair_uuid # every table that needs it
mix phoenix_kit.repair_uuid phoenix_kit_email_events
mix phoenix_kit.repair_uuid --dry-run # show the SQL, change nothing
mix phoenix_kit.repair_uuid --prefix tenant_aWhat it costs
ALTER COLUMN … TYPE uuid rewrites the table and holds an ACCESS EXCLUSIVE
lock for the duration — no reads, no writes, and behind a connection pooler
that means the pool fills rather than merely waiting. There is no concurrent
form of a type change; the size of the table is the size of the outage.
The primary key is cheaper here than in the migration: outside a transaction
the unique index is built CONCURRENTLY and then attached, so the exclusive
lock covers only the attach. That is why this task is not simply "V163 without
the limit".
Safety
Nothing is destructive except de-duplication, which deletes rows that share a
uuid — on a table that has run without a primary key those are the same
logical row stored twice, and a duplicate makes ADD PRIMARY KEY impossible.
--dry-run prints every statement, including the delete, without executing.
Values that cannot be cast to uuid abort that table with the query to
inspect them; other tables still proceed.