fix(historian): #687 re-review — a row at/before the Unix epoch is never a stored sample

With StartTime at or before the epoch, RequestStartFor has no margin left, so AVEVA's synthetic no-data/boundary row is stamped exactly at StartTime and was kept: raw reads returned a fabricated Bad sample at 1970-01-01 and the per-sample aggregates put it in bucket 0 (Start/End fabricated, Min/Max status Uncertain). IsWindowSample and the aggregate loop now drop any row with t <= ProbeFloor (RawAggregateReader.IsAfterFloor), matching the #686 walk-back's assumption.
2026-10-12 15:47:39 -04:00
parent 8114f13a28
commit a3ee917fb4
4 changed files with 43 additions and 2 deletions
@@ -473,6 +473,23 @@ public sealed class GatewayRawAggregateTests
        ds2.GetHealthSnapshot().TotalFailures.ShouldBe(1);
    }

+    [Theory] // a window starting AT the epoch gets no 1 ms margin, so AVEVA's no-data row is stamped at the window start:
+             // it must not become a stored Bad sample of bucket 0
+    [InlineData(HistoryAggregateType.Start)]
+    [InlineData(HistoryAggregateType.Count)]
+    [InlineData(HistoryAggregateType.Minimum)]
+    public async Task A_window_starting_at_the_epoch_does_not_evaluate_the_fabricated_row(HistoryAggregateType agg)
+    {
+        var epoch = DateTime.UnixEpoch;
+        var data = new[] { new StoredSample(epoch.AddSeconds(5), HistorianValue.FromDouble(7), Good) };
+        var fake = Store(data, avevaBoundary: true);
+        var s = (await Source(fake).ReadProcessedAsync("T", epoch, epoch.AddSeconds(20), TimeSpan.FromSeconds(20), agg, Ct))
+            .Samples.Single();
+        var expected = SqlBackendAnswer(agg, BucketPlan.Create(epoch, epoch.AddSeconds(20), TimeSpan.FromSeconds(20)), data).Single();
+        (s.Value, s.StatusCode).ShouldBe((expected.Value, expected.StatusCode));
+        fake.RawCalls[0].Start.ShouldBe(epoch); // the request start cannot go before the epoch
+    }
+
    [Fact] // #688: the default cap's budget fits the gateway's default ceiling, so a strict gateway serves the default config
    public async Task The_default_caps_row_budget_does_not_exceed_the_gateways_default_ceiling()
    {