_apply_facet_fields seeded cast_names from the cheap top-~20 listing only while
people_enriched_at was NULL, relying on "a sync never clears the watermark" to
protect an enriched fuller cast. Migration 0065 broke that assumption by nulling
people_enriched_at on every movie/show row, so the first post-deploy sync
downgraded enriched casts back to the listing top-20 — silently dropping
person-page cast-filter names for weeks until the backfill caught up (the S5b
regression, re-opened by the migration).
Guard structurally instead of trusting the watermark: union the listing cast
onto whatever is stored, never dropping a name already present. A fresh row
still seeds from the listing; a row whose watermark was reset but whose fuller
cast survives keeps it. Robust to any future watermark reset, not just 0065.
peter
f39c5bb25c