1. Uncapped reverse raw read on a forward-only backend = ONE forward read of the
window, filtered and reversed in memory (was a segment-by-segment walk).
2. Segment width is aimed at ~half the row budget from the density just observed
(overflow: from the truncated read's own sample span) and carried page to page
in HistoryContinuationState.SegmentWidthTicks.
3. The walk starts no later than now + 1 day and never reads before the epoch.
4. Request bounds are rounded outward to the millisecond, so a row AVEVA
fabricates at a rounded-up query start cannot land inside the segment.
5. Budget M = max(1, MaxTieClusterOverfetch); reads ask M + 2 rows, completeness is
'short OR last row past the segment', and a read crowded by rows before the
segment is re-read once (<= 2M + 4). A cluster of exactly M, neighbouring
clusters each within M, and M <= 1 are all served; only one timestamp over M
is refused. ServerHistorianOptions text updated.
6. The raw and events tie-path oversized-cluster refusal is BadTooManyOperations
(was BadHistoryOperationUnsupported), consistent with the walk.
7. GatewayHistorianDataSource.ReadRawAsync: a caller cancellation is not a backend
failure; NumValuesPerNode = 0 is sent as int.MaxValue (the client package and
the gateway reject max_values <= 0, so every uncapped Gateway raw read failed);
a MaxValuesCeiling refusal is a HistoryReadLimitExceededException.
8. Tests: upper-edge filter, epoch floor, look-ahead, ms alignment, exact/adjacent
clusters, minimal budget, carried density, and the walk over the real Gateway
source + FakeHistorianGatewayClient (OpcUaServer internals visible to it).
#669 turned an end-only capped HistoryRead-Raw into a reverse read (start > end)
for every backend; the gateway rejects start > end (InvalidArgument), so on the
default Gateway backend every end-only capped and every explicit reverse raw read
failed the node and was counted as a backend health failure.
- IHistorianDataSource.SupportsReverseRaw (default false; SqlServer/QuestDB/Null
true, Gateway false; guard test pins that every production backend declares it).
- OtOpcUaNodeManager sends a reverse window only to a backend that declares it;
otherwise ReverseRawReader walks (lo, hi] back in bounded forward segment reads
(1 min, x4 while sparse; each <= MaxTieClusterOverfetch + 1 rows; a full read is
re-read narrower, never answered truncated; filtered on sample timestamps, which
also drops AVEVA's fabricated query-start rows; stops at the Unix epoch). A
one-timestamp tie cluster over the bound => BadTooManyOperations.
- ServeRawPagedAsync maps HistoryReadLimitExceededException to BadTooManyOperations.
- GatewayHistorianDataSource.ReadRawAsync refuses start > end unsent, without
recording a health failure.
Average, Count, Minimum, Maximum, Range, Start, End, Delta and Minimum/MaximumActualTime are evaluated
on the Gateway backend from forward ReadRaw reads with BucketPlan + AggregateEvaluator, so Gateway
matches SqlServer/QuestDB exactly (values, status bits, interval-start stamps, #677 reverse).
- Window read [start - 1 ms, end] so AVEVA's initial-value row never lands in a bucket; a pre-window
row proves earlier data only with a non-Bad OPC quality (histsdk puts a value on every NULL row).
- Earlier data otherwise from a 2-row [1970, start) probe; later data from a 2-row [end, now+1d]
look-ahead; both ignore rows stamped at their query start/end.
- No gateway stream is ever abandoned (a client-side cancel makes the gateway evict its shared
historian session); past ServerHistorian:MaxTimeWeightedRawRows the bounded stream is drained, then
BadTooManyOperations. The gateway's max_values-ceiling InvalidArgument maps to the same limit; a
caller cancellation is not a backend fault.
- TimeAverage/Total stay AVEVA-native (no prior-sample read for exact Part 13 bounds), now stamped with
the interval start (PENDING the live leg: histsdk's tail+43 start_time field is unverified) and
carrying the Calculated bits.
- Served set: GatewayHistorianDataSource.ServedAggregates (12). Live AVEVA leg open (VPN).
IHistorianDataSource.SupportedAggregates (default: every HistoryAggregateType)
is the one authority for both ServerCapabilities/AggregateFunctions (i=2997) and
HistoryServerCapabilities/AggregateFunctions (i=11201) and for the up-front
BadAggregateNotSupported in HistoryRead-Processed. Gateway declares
AggregateModeMapper.Served (4), SqlServer/QuestDB AggregateFamilies.Served (17),
Null none. Only the folder references are trimmed; the SDK's calculator
factories stay so live AggregateFilter subscriptions keep working.
Co-Authored-By: Claude <noreply@anthropic.com>
- IHistorianDataSource.SupportsReverseEvents (default false; SqlServer/QuestDB true; Gateway/Null declare false).
The node manager checks it BEFORE calling the source: an end-only capped events read becomes reverse only on
a supporting backend (Gateway, the default, keeps the pre-#675 forward [MinValue, EndTime) paging), and an
explicit reverse read on a non-supporting backend is BadHistoryOperationUnsupported without a call.
- Removed the broad catch (NotSupportedException) in the events path: a NotSupportedException from inside a
backend is now logged as a backend fault (Error), not an 'unsupported' Warning.
- Null declares the reverse overload itself; guard test: every production IHistorianDataSource declares both
the reverse overload and the capability (positive-control scan of all four backends).
- Conformance: capability reported + oversized reverse tie cluster (forward over-fetch reversed == reverse
read order; capped reverse read stopping inside the cluster flags truncation) on SqlServer + QuestDB.
- docs/Historian.md: end-only capped events read is backward on SqlServer/QuestDB, forward on Gateway.
- IHistorianDataSource.ReadEventsAsync(..., bool reverse, ...) overload: reverse = Part 11 window (lo, hi]
newest-first by (time, id) DESC. Default forwards forward reads and throws NotSupportedException for
reverse (Null); Gateway refuses explicitly (ascending-only stream). Server answers
BadHistoryOperationUnsupported instead of silently returning the earliest N ascending.
- SqlServer / QuestDB serve reverse natively (ORDER BY time DESC, id DESC + TOP/LIMIT).
- Node manager: reverse event reads page with continuation points; direction stored in the cursor
(HistoryContinuationState.Reverse) so a resume continues in the cursor's direction; reverse tie clusters
over-fetched forward and sliced from the newest end (SliceTieCluster(reverse:)); end-only reads with a
cap page backward from EndTime (mirrors raw).
- Resumed event pages over-fetch by the boundary skip, so every non-final page is a full cap page.
- Tests: node-manager reverse paging (ties, clusters, coarse resolution, overfetch bound, resume
direction both ways, end-only, unsupported backend); shared EventReadConformance on SqlServer +
QuestDB; over-the-wire reverse paging; offline Gateway pin of the UTC DateTime.MaxValue bound through
the published client's proto conversion (in-process gRPC capture) and FILETIME.
- docs/Historian.md event paging section.
Adds <summary>/<param>/<returns>/<inheritdoc> where missing and removes
project bookkeeping IDs (task/tracking refs) from shipped code comments,
so the docs read cleanly and CommentChecker is quiet except for known
false positives (PLC/protocol terms, event/IEqualityComparer inheritdoc).
Doc/comment-only; no logic changed; solution builds clean.
The HistorianGateway driver is now the sole historian read/write+alarm backend, so the
Wonderware sidecar projects are dead code. Removes the 5 Wonderware projects (driver,
.Client, .Client.Contracts, + their 2 test projects) from the solution and tree, and fully
retires the vestigial 'Historian.Wonderware' driver type (UI/probe-only; it had no driver
factory): the Host probe registration, the AdminUI driver-config surface (driver page,
tag-config editor/model/validator entry, address picker/builder, driver-type catalog +
dropdown + edit-router entries), and their tests. Prunes the now-unused Wonderware
connection fields (Host/Port/UseTls/ServerCertThumbprint/SharedSecret) from
AlarmHistorianOptions (keeping Enabled + the SQLite store-and-forward knobs) and refreshes
the stale XML docs that named Wonderware as the production backend.
Claude-Session: https://claude.ai/code/session_012SDSQ3AcaXqPcBtDESBRii
Addresses T7/T8/T11 code-review minors: route the sync dispose through DisposeAsync
so a double Dispose()+DisposeAsync() stays a no-op; cover the sync path.
Claude-Session: https://claude.ai/code/session_012SDSQ3AcaXqPcBtDESBRii
Joseph Doherty