R1 adversarial review surfaced 5 issues, all addressed:
#1 chunked download silently disabled in non-Caddy deployments (HEAD on
GET-only FastAPI route returns 405). _probe_range_support now falls back
to GET with Range: bytes=0-0 when HEAD fails — works against both
Caddy file_server (HEAD-friendly) and dev FastAPI direct (GET-only).
#2 parse-error fallback heuristic too broad — matched on Unrecognized
name / Function not found / No matching signature / Invalid cast,
which BQ surfaces for ordinary user-column typos. That triggered slow
ATTACH-catalog retry on every typo (2× latency tax). Narrowed to just
'Syntax error' / 'syntax error' which are the genuine DuckDB-vs-BQ
dialect mismatch markers.
#3 apply_bq_session_settings was only run on fresh-built pool entries,
not on reuse. An operator's /admin/server-config change to bq_query
_timeout_ms wouldn't propagate to long-lived pooled sessions until
restart. Fixed: re-apply on every pool acquire (idempotent + fail-soft).
#4 content-length sanity bound — a misconfigured proxy returning a
wildly inflated Content-Length would cause overlapping chunked Range
requests against the actual file → corrupt assembled output (caught
by manifest hash check, but only after wasted bandwidth). Cap at 100
GiB; above that, drop to single-stream.
#5 rewriter assumed every BQ row resolves under the single
bq.projects.data project. Bucket containing '.' suggests a project-
qualified bucket (multi-project deployment); rewriter would silently
target the wrong project. Conservative skip with regression test.
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