Fix operator self-time for parents of Compute Scalar (#215 C5) + one decimal on benefit % (#255)

C5 (operator self-time look-through):
GetSerialOwnElapsed subtracted each direct child's ActualElapsedMs, but
Compute Scalar operators don't carry runtime stats (ActualElapsedMs = 0).
For an operator whose direct children are Compute Scalars — like the node-6
Hash Match in Joe's private plan — that meant "children elapsed = 0" and the
parent kept its full elapsed as self-time.

Effect: node-6 Hash Spill reported 95% benefit / 8,829ms self-time. With
look-through through the Compute Scalars it's 1,609ms self-time / 17.4% —
matching Joe's math of 8.829 - 7.121 - 0.099.

New GetEffectiveChildElapsedMs helper walks through pass-through operators
(Compute Scalar and anything else missing runtime stats) to the first
descendant with real stats. Parallelism exchange children keep existing
max-child behavior because exchange times are unreliable.

Applies to every operator-time-based benefit score (spills, key lookups,
bare scans, scan-with-predicate, scan cardinality, eager index spool, etc).

C2 (decimal precision on benefit %):
Benefit % was rounded to N0 everywhere, so tiny waits showed as "up to 0%".
Switched to one decimal except for 100 (shown as "100"), matching the
existing pattern in ComparisonFormatter. Applied to web strip, wait-stats
card, HTML export (both surfaces), text formatter (both paths), Avalonia
Plan Warnings + Node Warnings headers.

Version bump 1.7.1 -> 1.7.2.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: erikdarlingdata

src/PlanViewer.App/Controls/PlanViewerControl.axaml.cs

@@ -801,6 +801,9 @@ private static string FormatBytes(double bytes)
         return $"{bytes / (1024L * 1024 * 1024):N1} GB";
     }
 
+    private static string FormatBenefitPercent(double pct) =>
+        pct >= 100 ? $"{pct:N0}" : $"{pct:N1}";
+
     #endregion
 
     #region Node Selection & Properties Panel
@@ -1737,7 +1740,7 @@ private void ShowPropertiesPanel(PlanNode node)
                         : w.Severity == PlanWarningSeverity.Warning ? "#FFB347" : "#6BB5FF";
                     var warnPanel = new StackPanel { Margin = new Thickness(10, 2, 10, 2) };
                     var planWarnHeader = w.MaxBenefitPercent.HasValue
-                        ? $"\u26A0 {w.WarningType} \u2014 up to {w.MaxBenefitPercent:N0}% benefit"
+                        ? $"\u26A0 {w.WarningType} \u2014 up to {FormatBenefitPercent(w.MaxBenefitPercent.Value)}% benefit"
                         : $"\u26A0 {w.WarningType}";
                     warnPanel.Children.Add(new TextBlock
                     {
@@ -1819,7 +1822,7 @@ private void ShowPropertiesPanel(PlanNode node)
                     : w.Severity == PlanWarningSeverity.Warning ? "#FFB347" : "#6BB5FF";
                 var warnPanel = new StackPanel { Margin = new Thickness(10, 2, 10, 2) };
                 var nodeWarnHeader = w.MaxBenefitPercent.HasValue
-                    ? $"\u26A0 {w.WarningType} \u2014 up to {w.MaxBenefitPercent:N0}% benefit"
+                    ? $"\u26A0 {w.WarningType} \u2014 up to {FormatBenefitPercent(w.MaxBenefitPercent.Value)}% benefit"
                     : $"\u26A0 {w.WarningType}";
                 warnPanel.Children.Add(new TextBlock
                 {

src/PlanViewer.App/PlanViewer.App.csproj

@@ -6,7 +6,7 @@
     <ApplicationManifest>app.manifest</ApplicationManifest>
     <ApplicationIcon>EDD.ico</ApplicationIcon>
     <AvaloniaUseCompiledBindingsByDefault>true</AvaloniaUseCompiledBindingsByDefault>
-    <Version>1.7.1</Version>
+    <Version>1.7.2</Version>
     <Authors>Erik Darling</Authors>
     <Company>Darling Data LLC</Company>
     <Product>Performance Studio</Product>

src/PlanViewer.Core/Output/HtmlExporter.cs

@@ -407,7 +407,7 @@ private static void WriteWaitStatsCard(StringBuilder sb, StatementResult stmt, b
             {
                 var barPct = maxWait > 0 ? (double)w.WaitTimeMs / maxWait * 100 : 0;
                 var benefitTag = benefitLookup.TryGetValue(w.WaitType, out var pct)
-                    ? $" <span class=\"warn-benefit\">up to {pct:N0}%</span>"
+                    ? $" <span class=\"warn-benefit\">up to {(pct >= 100 ? pct.ToString("N0") : pct.ToString("N1"))}%</span>"
                     : "";
                 sb.AppendLine("<div class=\"wait-row\">");
                 sb.AppendLine($"<span class=\"wait-type\">{Encode(w.WaitType)}</span>");
@@ -458,7 +458,7 @@ private static void WriteWarnings(StringBuilder sb, StatementResult stmt)
                 sb.AppendLine($"<span class=\"warn-op\">{Encode(w.Operator)}</span>");
             sb.AppendLine($"<span class=\"warn-type\">{Encode(w.Type)}</span>");
             if (w.MaxBenefitPercent.HasValue)
-                sb.AppendLine($"<span class=\"warn-benefit\">up to {w.MaxBenefitPercent:N0}% benefit</span>");
+                sb.AppendLine($"<span class=\"warn-benefit\">up to {(w.MaxBenefitPercent.Value >= 100 ? w.MaxBenefitPercent.Value.ToString("N0") : w.MaxBenefitPercent.Value.ToString("N1"))}% benefit</span>");
             sb.AppendLine($"<span class=\"warn-msg\">{Encode(w.Message)}</span>");
             if (!string.IsNullOrEmpty(w.ActionableFix))
                 sb.AppendLine($"<span class=\"warn-fix\">{Encode(w.ActionableFix)}</span>");

src/PlanViewer.Core/Output/TextFormatter.cs

@@ -139,7 +139,7 @@ public static void WriteText(AnalysisResult result, TextWriter writer)
                 foreach (var w in stmt.WaitStats.OrderByDescending(w => w.WaitTimeMs))
                 {
                     var benefitTag = benefitLookup.TryGetValue(w.WaitType, out var pct)
-                        ? $" (up to {pct:N0}% benefit)"
+                        ? $" (up to {(pct >= 100 ? pct.ToString("N0") : pct.ToString("N1"))}% benefit)"
                         : "";
                     writer.WriteLine($"  {w.WaitType}: {w.WaitTimeMs:N0}ms{benefitTag}");
                 }
@@ -169,7 +169,7 @@ public static void WriteText(AnalysisResult result, TextWriter writer)
                 foreach (var w in sortedWarnings)
                 {
                     var benefitTag = w.MaxBenefitPercent.HasValue
-                        ? $" (up to {w.MaxBenefitPercent:N0}% benefit)"
+                        ? $" (up to {(w.MaxBenefitPercent.Value >= 100 ? w.MaxBenefitPercent.Value.ToString("N0") : w.MaxBenefitPercent.Value.ToString("N1"))}% benefit)"
                         : "";
                     writer.WriteLine($"  [{w.Severity}] {w.Type}{benefitTag}: {EscapeNewlines(w.Message)}");
                     if (!string.IsNullOrEmpty(w.ActionableFix))

src/PlanViewer.Core/Services/PlanAnalyzer.cs

@@ -1593,26 +1593,45 @@ private static long GetPerThreadOwnElapsed(PlanNode node)
     }
 
     /// <summary>
-    /// Serial row mode self-time: subtract all direct children's elapsed.
-    /// Exchange children are skipped through to their real child.
+    /// Serial row mode self-time: subtract all direct children's effective elapsed.
+    /// Pass-through operators (Compute Scalar, etc.) don't carry runtime stats —
+    /// look through them to the first descendant that does. Exchange children
+    /// use max-child elapsed because exchange times are unreliable.
     /// </summary>
     private static long GetSerialOwnElapsed(PlanNode node)
     {
         var totalChildElapsed = 0L;
         foreach (var child in node.Children)
-        {
-            var childElapsed = child.ActualElapsedMs;
-
-            // Exchange operators have unreliable times — skip to their child
-            if (child.PhysicalOp == "Parallelism" && child.Children.Count > 0)
-                childElapsed = child.Children.Max(c => c.ActualElapsedMs);
-
-            totalChildElapsed += childElapsed;
-        }
+            totalChildElapsed += GetEffectiveChildElapsedMs(child);
 
         return Math.Max(0, node.ActualElapsedMs - totalChildElapsed);
     }
 
+    /// <summary>
+    /// Returns the elapsed time a child contributes to its parent's subtree.
+    /// Looks through pass-through operators (Compute Scalar, Parallelism exchange)
+    /// that don't carry reliable runtime stats.
+    /// </summary>
+    private static long GetEffectiveChildElapsedMs(PlanNode child)
+    {
+        // Exchange operators: unreliable times, use max child
+        if (child.PhysicalOp == "Parallelism" && child.Children.Count > 0)
+            return child.Children.Max(GetEffectiveChildElapsedMs);
+
+        // Child has its own stats: use them
+        if (child.ActualElapsedMs > 0)
+            return child.ActualElapsedMs;
+
+        // No stats (Compute Scalar and similar): look through to descendants
+        if (child.Children.Count == 0)
+            return 0;
+
+        var sum = 0L;
+        foreach (var grandchild in child.Children)
+            sum += GetEffectiveChildElapsedMs(grandchild);
+        return sum;
+    }
+
     /// <summary>
     /// Calculates a Parallelism (exchange) operator's own elapsed time.
     /// Exchange times are unreliable — they accumulate wait time caused by

src/PlanViewer.Web/Pages/Index.razor

@@ -302,7 +302,7 @@ else
                                 @w.WaitTimeMs.ToString("N0") ms
                                 @if (benefitPct > 0)
                                 {
-                                    <span class="wait-benefit">up to @benefitPct.ToString("N0")%</span>
+                                    <span class="wait-benefit">up to @(benefitPct >= 100 ? benefitPct.ToString("N0") : benefitPct.ToString("N1"))%</span>
                                 }
                             </span>
                         </div>
@@ -346,7 +346,7 @@ else
                         <span class="warning-type">@w.Type</span>
                         @if (w.MaxBenefitPercent.HasValue)
                         {
-                            <span class="warn-benefit">up to @w.MaxBenefitPercent.Value.ToString("N0")% benefit</span>
+                            <span class="warn-benefit">up to @(w.MaxBenefitPercent.Value >= 100 ? w.MaxBenefitPercent.Value.ToString("N0") : w.MaxBenefitPercent.Value.ToString("N1"))% benefit</span>
                         }
                         <span class="warning-msg">@w.Message</span>
                         @if (!string.IsNullOrEmpty(w.ActionableFix))