The inline INSERT…SELECT backfill in migration 0045 wrapped the table
creation and a ~100 GB pass over image_record.tagger_predictions in one
transaction: nothing committed until the end, it was unmonitorable, and an
earlier MATERIALIZED-CTE form spilled the full 100 GB to temp on NFS. A
deploy got stuck on it for ~2h with image_prediction never appearing.
Split the concerns:
- 0045 now creates ONLY the table + indexes (instant DDL → web boots).
- New backend.app.tasks.admin.backfill_image_predictions_task copies the
>= store-floor predictions from the JSON into image_prediction, batched by
id window and committed per chunk: live progress, resumable (re-enqueues
from the last committed id), idempotent (ON CONFLICT DO NOTHING). json_each
stays in the DB executor streaming each window — no Python-side 100 GB load,
no materialization.
- POST /api/admin/maintenance/backfill-predictions + a Maintenance-tab card
to trigger the one-time run after upgrading.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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