read_sql resolves connection_ref from the environment to a sqlite path, opens it read-only (mode=ro so a write in the query fails at the DB), and converts cells to their spec-5 text form: INTEGER plain decimal, REAL shortest round-trip (repr), TEXT verbatim, SQL NULL empty string, BLOB/other IngestError (never silent coercion). materialize now dispatches file->read_csv, sql->read_sql; http stays I6-refused. Pure stdlib (sqlite3/os/contextlib) — MAF-free context-seam guard intact. No spec change (frozen); the SQL type/number rules were delegated to I4.
Refs: shared/ingest-spec.md 4/5/8 · sesjonsplan I4
