Code-review Minor: the record typed ParameterNames/Parameters/Members/
SelectedColumns as IReadOnlyList<T> but was handed the planner's live List<T>
instances. SqlQueryPlan documents itself as safe to hold for plan caching, so
an aliased list is a real hazard once the reader starts reusing plans across
polls: IReadOnlyList<T> is downcastable, and one mutation would corrupt every
subsequent poll served by that plan.
Copying at the record boundary fixes it for every call site at once rather
than relying on each planner branch remembering to call AsReadOnly.
Pinned by a test that mutates the caller's lists after construction; verified
load-bearing (reverting the record turns it red).
Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
Executes a poll pass: resolve refs -> SqlGroupPlanner.Plan -> one command per
group -> slice the result set back to per-tag DataValueSnapshots, positionally
aligned with the caller's reference list (design §3.2).
The frozen-peer contract (design §8.3, the R2-01 S7 lesson) is the core of it.
CommandTimeout is only the server-side backstop; the client-side bound is a
linked CancelAfter PLUS Task.WaitAsync, because a linked token bounds only a
provider that honours it and ADO.NET providers vary. The whole per-group
operation — waiting for a concurrency slot, OpenAsync, and the query — runs off
one operationTimeout budget, so ReadAsync returns on time regardless of what the
database is doing. A breach Bad-codes that group (BadTimeout); caller
cancellation propagates instead, since nobody consumes a torn-down poll.
Also: absent row (BadNoData) stays distinct from a NULL cell (Uncertain, or Bad
under nullIsBad); duplicate plan members are all fed (two tags on one keyValue
bind one parameter but stay two members); the concurrency slot is released by the
work, not the waiter, so a frozen database can never hold more than
maxConcurrentGroups connections; the whole call throws only when the connection
itself cannot open, which is what earns PollGroupEngine's backoff.
SqlStatusCodes is driver-local, matching every sibling driver's own table — there
is no shared helper in Core.Abstractions and drivers do not reference the OPC UA
SDK. Values were read off Opc.Ua.StatusCodes rather than copied from a sibling,
because two of those tables carry transcription errors.
Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
Three findings from the code review of the dialect seam:
- QuoteIdentifier used char.IsControl, which only covers Unicode category Cc.
Bidi overrides, zero-width spaces, soft hyphen and BOM are category Cf and
passed through untouched. They cannot escape the brackets, so this is not an
injection bypass — but the method rejects control characters precisely to
protect the integrity of logged/audited statements, and Cf characters spoof
rendered text while comparing byte-different from the real catalog name
(Trojan Source, CVE-2021-42574). Same rule, same rationale, wider category.
- The XML docs on both files asserted that identifiers 'are sourced only from
catalog-validated (INFORMATION_SCHEMA) names' and that rejection is 'a
backstop, not the primary defence'. Neither is true yet: design §8.1 does
specify that gate, but nothing implements it and no task in the plan
schedules one, so an authored TagConfig table/column reaches QuoteIdentifier
unfiltered. The docs now say so, because under-scrutinising this method on
the strength of a filter that does not exist is exactly the failure mode.
- The control-character test only pinned NUL, so a regression to a
Contains('\0') check would still have passed. Pinned the whole Cc category
plus the new Cf rule; verified load-bearing by deleting the guard and
observing exactly the 5 new cases go red.
Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
The dialect owns the two things ADO.NET's System.Data.Common base types
cannot abstract: identifier quoting and the metadata-catalog SQL. It is
the driver's SQL-injection boundary — values always bind as DbParameters,
identifiers cannot, so the few that reach a command text are catalog-
sourced and pass through QuoteIdentifier.
QuoteIdentifier brackets one identifier part and doubles embedded ] (the
only metacharacter that can terminate a bracketed identifier early);
rejects null/empty/whitespace, >128 chars (T-SQL sysname ceiling), and any
control character (incl. NUL) as ArgumentException, without echoing the
untrusted value into the message. MapColumnType folds the design §3.7
families case-insensitively and never throws — an unrecognised family
falls back to String so a browse over an exotic column still renders;
timestamp/rowversion and time are deliberately NOT mapped to DateTime.
Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
Joseph Doherty