Replace the per-cell parquet cache with TimescaleDB hypertables as the
production backend for the raw daily climate record, and drop pg_duckdb.
Parquet stays the backend whenever THERMOGRAPH_DATABASE_URL is not a
Postgres URL (dev, tests, offline tooling), the same dialect switch the
accounts DB and derived store already use, so CI stays Postgres-free.
- data/climate_store.py: psycopg + polars bridge over climate_history
(a hypertable), climate_recent, and climate_sync (per-cell freshness).
Reads via pl.read_database, writes via COPY + ON CONFLICT upsert;
fail-soft to a cache miss so a DB hiccup degrades to upstream refetch.
- data/climate.py: route every cache/mtime touchpoint through a backend
dispatch. recent_stamp becomes int(recent_synced_at) on Postgres; the
stale-serve path still avoids bumping it, so derived-payload tokens
invalidate on exactly the same events as before.
- alembic 0002: CREATE EXTENSION timescaledb plus the hypertable schema
(compression policy on year-old chunks), guarded to no-op off Postgres.
- migrate_cache_to_pg.py (make migrate-cache): idempotent backfill of the
parquet cache into the hypertables, preserving file mtimes as sync
timestamps so recent_stamp is unchanged across cutover.
- db image -> stock timescale/timescaledb:latest-pg18; drop the custom
pg_duckdb Dockerfile, the read-only /parquet mount, and the duckdb
tuning GUC. Docs updated for the new backend and cutover.
Co-authored-by: Claude <noreply@anthropic.com>
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