Merge pull request #217 from erikdarlingdata/fix/wait-stats-cleanup

Strip operator-level wait noise, add query classification

Author: erikdarlingdata

src/PlanViewer.App/Services/AdviceContentBuilder.cs

@@ -1126,6 +1126,41 @@ private static SolidColorBrush GetWaitCategoryBrush(string waitType)
             items.Add(($"Memory grant: {grantedMB:F1} MB ({usedPct:F0}% used)", memBrush));
         }
 
+        // Wait profile classification
+        if (stmt.WaitStats.Count > 0)
+        {
+            var totalMs = stmt.WaitStats.Sum(w => w.WaitTimeMs);
+            if (totalMs > 0)
+            {
+                long ioMs = 0, cpuMs = 0, parallelMs = 0, lockMs = 0;
+                foreach (var w in stmt.WaitStats)
+                {
+                    var wt = w.WaitType.ToUpperInvariant();
+                    if (wt.StartsWith("PAGEIOLATCH") || wt.Contains("IO_COMPLETION"))
+                        ioMs += w.WaitTimeMs;
+                    else if (wt == "SOS_SCHEDULER_YIELD")
+                        cpuMs += w.WaitTimeMs;
+                    else if (wt.StartsWith("CX"))
+                        parallelMs += w.WaitTimeMs;
+                    else if (wt.StartsWith("LCK_"))
+                        lockMs += w.WaitTimeMs;
+                }
+
+                // Pick the dominant category (>= 30% of total)
+                var categories = new List<(string label, long ms)>();
+                if (ioMs * 100 / totalMs >= 30) categories.Add(("I/O", ioMs));
+                if (cpuMs * 100 / totalMs >= 30) categories.Add(("CPU", cpuMs));
+                if (parallelMs * 100 / totalMs >= 30) categories.Add(("parallelism", parallelMs));
+                if (lockMs * 100 / totalMs >= 30) categories.Add(("lock contention", lockMs));
+
+                if (categories.Count > 0)
+                {
+                    var label = string.Join(" + ", categories.Select(c => c.label));
+                    items.Add(($"{label} bound ({totalMs:N0}ms total wait time)", InfoBrush));
+                }
+            }
+        }
+
         // Warning counts by severity
         var criticalCount = stmt.Warnings.Count(w =>
             w.Severity.Equals("Critical", StringComparison.OrdinalIgnoreCase));

src/PlanViewer.Core/Services/PlanAnalyzer.cs

@@ -548,9 +548,9 @@ private static void AnalyzeNode(PlanNode node, PlanStatement stmt, AnalyzerConfi
         {
             // Gate: skip trivial filters based on actual stats or estimated cost
             bool isTrivial;
-            long childReads = 0;
             if (node.HasActualStats)
             {
+                long childReads = 0;
                 foreach (var child in node.Children)
                     childReads += SumSubtreeReads(child);
                 var childElapsed = node.Children.Max(c => c.ActualElapsedMs);
@@ -571,14 +571,6 @@ private static void AnalyzeNode(PlanNode node, PlanStatement stmt, AnalyzerConfi
                     message += $"\n{impact}";
                 message += $"\nPredicate: {predicate}";
 
-                // Wait stats add context — rows burned CPU/I/O/waits just to be discarded
-                if (childReads >= 1000)
-                {
-                    var waitContext = GetTopWaitContext(stmt.WaitStats);
-                    if (waitContext != null)
-                        message += $"\n{waitContext}";
-                }
-
                 node.Warnings.Add(new PlanWarning
                 {
                     WarningType = "Filter Operator",
@@ -655,16 +647,10 @@ private static void AnalyzeNode(PlanNode node, PlanStatement stmt, AnalyzerConfi
                         var actualDisplay = executions > 1
                             ? $"Actual {node.ActualRows:N0} ({actualPerExec:N0} rows x {executions:N0} executions)"
                             : $"Actual {node.ActualRows:N0}";
-                        var message = $"Estimated {node.EstimateRows:N0} vs {actualDisplay} — {factor:F0}x {direction}. {harm}";
-
-                        var waitContext = GetTopWaitContext(stmt.WaitStats);
-                        if (waitContext != null)
-                            message += $" {waitContext}";
-
                         node.Warnings.Add(new PlanWarning
                         {
                             WarningType = "Row Estimate Mismatch",
-                            Message = message,
+                            Message = $"Estimated {node.EstimateRows:N0} vs {actualDisplay} — {factor:F0}x {direction}. {harm}",
                             Severity = factor >= 100 ? PlanWarningSeverity.Critical : PlanWarningSeverity.Warning
                         });
                     }
@@ -848,10 +834,6 @@ _ when nonSargableReason.StartsWith("Function call") =>
                 message += $" {details.Summary}";
             message += " Check that you have appropriate indexes.";
 
-            var waitContext = GetTopWaitContext(stmt.WaitStats);
-            if (waitContext != null)
-                message += $" {waitContext}";
-
             // I/O waits specifically confirm the scan is hitting disk — elevate
             if (HasSignificantIoWaits(stmt.WaitStats) && details.CostPct >= 50
                 && severity != PlanWarningSeverity.Critical)
@@ -1047,10 +1029,6 @@ _ when nonSargableReason.StartsWith("Function call") =>
                 else
                     details.Add("Consider whether a hash or merge join would be more appropriate for this row count.");
 
-                var waitContext = GetTopWaitContext(stmt.WaitStats);
-                if (waitContext != null)
-                    details.Add(waitContext);
-
                 node.Warnings.Add(new PlanWarning
                 {
                     WarningType = "Nested Loops High Executions",
@@ -1839,33 +1817,6 @@ private static bool HasSignificantIoWaits(List<WaitStatInfo> waits)
         return ioMs >= 100 && pct >= 20;
     }
 
-    /// <summary>
-    /// Returns a terse sentence describing the dominant wait type for appending
-    /// to an existing warning message, or null if waits are negligible.
-    /// Surfaces whatever wait type is dominant — PAGEIOLATCH, SOS_SCHEDULER_YIELD,
-    /// CXPACKET, LCK_*, HTBUILD, EXECSYNC, IO_COMPLETION, etc.
-    /// Threshold: top wait >= 100ms and >= 20% of total wait time.
-    /// </summary>
-    private static string? GetTopWaitContext(List<WaitStatInfo> waits)
-    {
-        if (waits.Count == 0)
-            return null;
-
-        var totalMs = waits.Sum(w => w.WaitTimeMs);
-        if (totalMs == 0)
-            return null;
-
-        var top = waits.OrderByDescending(w => w.WaitTimeMs).First();
-        if (top.WaitTimeMs < 100)
-            return null;
-
-        var pct = (double)top.WaitTimeMs / totalMs * 100;
-        if (pct < 20)
-            return null;
-
-        return $"Dominant wait: {top.WaitType} ({top.WaitTimeMs:N0}ms, {pct:N0}% of total wait time).";
-    }
-
     private static bool AllocatesResources(PlanNode node)
     {
         // Operators that get memory grants or allocate structures based on row estimates.