M1: the time-weighted family (incl. Total, formerly a pushed-down SUM) streams
raw window rows into the C# evaluator. New shared knob
ServerHistorian:MaxTimeWeightedRawRows (default 1,000,000; <=0 unbounded with a
Validate warning) flows through HistorianBackendRegistry into both providers.
The window query is capped at cap+1 (SQL Server TOP (@maxRows), QuestDB LIMIT $4);
one row past the cap throws the new Core.Abstractions
HistoryReadLimitExceededException, which the node manager maps to
BadTooManyOperations for that node. Not counted as a backend health failure;
bound rows are not counted; per-sample aggregates are not capped.
M2: reverse Interpolative is anchored at the later time (Part 13): points at
End - i*interval, emitted latest first. 10:00->09:00 @1h yields 10:00.
L1: Partial bit (0x4, = Opc.Ua.AggregateBits.Partial) on non-Bad results of a
truncated last interval (time-weighted family; per-sample family is a follow-up).
L2/L3: aligned with the SDK AggregateCalculator.GetTimeBasedStatusCode
(decompiled from Opc.Ua.Server 1.5.378.106): TreatUncertainAsBad=false counts
Uncertain time (Uncertain samples, held-into-outage, extrapolation) as Good
time; data but no non-Bad time => generic Bad (0x80000000); BadNoData only
when there is no data at all. Consequence: a live tag's latest interval reads
Good (documented).
L5: release note no longer claims Total matches the Gateway Integral exactly
(AVEVA's divisor is unverified); it notes Total is now evaluated in C# and
subject to the cap.
Tests: unit (reverse Interpolative x3, Partial, Bad vs BadNoData incl. an
open-ended outage, cap helpers, SDK bit oracles); conformance (reverse
Interpolative, raw-row cap at/over/0, bounds not counted, health unaffected);
node manager BadTooManyOperations; options default + warning. Each new
behaviour falsified by mutation (aggregator x9, data-source cap checks on
both backends against the real DBs, node-manager catch).
Joseph Doherty
56bb4855bb