A backup written before migration 0420 files Fitbit and Google Health
HRV as HEART_RATE_VARIABILITY, and the restore wrote it back verbatim,
undoing the migration for the account (and able to duplicate an
HRV_RMSSD row of the same night, since type is part of the unique key).
The restore now applies the same move: those rows come back as
HRV_RMSSD, a legacy row whose RMSSD twin the file also holds is skipped,
and SDNN personal records set by them are left out as the migration
deleted them.
Four models leave the coverage-pending register with both ends and a
round-trip proof: PersonalRecord, UserAchievement, EnvironmentContext and
EnvironmentTravelLocation. Two new section modules hold reader and restore
beside each other, the arrangement the visits, vaccinations, reminders and
Coach sections already use.
The register understated two of them. The bests are "recomputable in
principle", which is true and does not help: nothing recomputes them, and a
recomputation over a restored history would find different rows, because
sample series and GPS routes never travel, a portable file omits deleted
readings, and a record set in a reading that has since been corrected cannot
be found twice. The badge's unlock date is worse. The evaluator prefers a
persisted date over a derived one, and several of the dates it can still
derive come from counters no backup carries, so a dropped row does not relock
the badge, it re-earns it today.
PersonalRecord.sourceMeasurementId is the reference that needed care, and it
is the dangerous kind. The schema declares no relation for it; migration 0054
created the column as a real foreign key against measurements. Writing it
blind is not a dangling pointer, it is a constraint violation that rolls the
whole restore back and hands the operator an empty account. Measured, with the
resolution removed: "Foreign key constraint violated on the constraint:
personal_records_source_measurement_id_fkey", HTTP 500, nothing restored. So
the restore runs after the measurements, resolves the pointer against the rows
it actually wrote, nulls what it cannot resolve and reports it under a new
personalRecordReference skip kind.
An unlocked badge names a definition in the code catalogue, which drifts
between the release that writes a file and the one that reads it. The id is
carried and written back verbatim rather than judged, the same answer the
vaccination restore gives an antigen slug it cannot resolve.
The readings and the location periods travel as a pair because carrying the
readings alone is worse than losing them. The environment resolver reads the
periods live, so with them gone the nightly seven-day lookback re-resolves
every trip day to the home location and upserts over the row: an account would
come back with a fortnight abroad and then have it quietly rewritten as a
fortnight at home, days after a restore that reported success. Day keys stay
strings end to end, and fetchedAt is restored verbatim so a two-year-old
provisional reading does not claim it was confirmed today.
The round trip seeds bests that share a metric type and an instant and differ
only in the sport slot, two badges earned years apart (one of them under an id
this build no longer defines), and a trip day beside a home day, then reads
each back column by column. Counting alone passes every one of the failures
worth fearing here: slots dropped so a 5 km best is presented as a 10 km best,
unlock dates stamped at restore time, a trip day re-attributed to the home
city, a location period whose bounds no longer cover the reading it explains.
Each of those was applied on purpose and each failed on its own assertion.
Two schema comments claimed no read path selects a column that this backup now
selects; both say what reads it instead of staying wrong.
Marc-André Bombeck