From 19a008b4abfd9d0f1ab1684006220070842072da Mon Sep 17 00:00:00 2001
From: Erik Darling <2136037+erikdarlingdata@users.noreply.github.com>
Date: Mon, 6 Apr 2026 23:43:16 -0400
Subject: [PATCH] Gate XML MemoryGrantWarning at 1 GB to match Rule 9 threshold

The plan XML's MemoryGrantWarning element fires for any grant size, including
trivially small ones (1 MB). Gate at 1 GB to suppress noise, consistent with
the analyzer's Rule 9 threshold. All values confirmed as KB across all example
plans. Updated test to verify small grants are suppressed.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 src/PlanViewer.Core/Services/ShowPlanParser.cs | 18 ++++++++++++------
 .../PlanViewer.Core.Tests/PlanAnalyzerTests.cs |  9 +++++----
 2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/src/PlanViewer.Core/Services/ShowPlanParser.cs b/src/PlanViewer.Core/Services/ShowPlanParser.cs
index 5cf9f11..62ebf42 100644
--- a/src/PlanViewer.Core/Services/ShowPlanParser.cs
+++ b/src/PlanViewer.Core/Services/ShowPlanParser.cs
@@ -1665,7 +1665,8 @@ private static List<PlanWarning> ParseWarningsFromElement(XElement warningsEl)
             });
         }
 
-        // Memory grant warning
+        // Memory grant warning (from plan XML) — gate at 1 GB to avoid noise on small grants
+        // All values are in KB, consistent with MemoryGrantInfo element
         var memWarnEl = warningsEl.Element(Ns + "MemoryGrantWarning");
         if (memWarnEl != null)
         {
@@ -1673,12 +1674,17 @@ private static List<PlanWarning> ParseWarningsFromElement(XElement warningsEl)
             var requested = ParseLong(memWarnEl.Attribute("RequestedMemory")?.Value);
             var granted = ParseLong(memWarnEl.Attribute("GrantedMemory")?.Value);
             var maxUsed = ParseLong(memWarnEl.Attribute("MaxUsedMemory")?.Value);
-            result.Add(new PlanWarning
+            if (granted >= 1048576) // 1 GB in KB
             {
-                WarningType = "Memory Grant",
-                Message = $"{kind}: Requested {requested:N0} KB, Granted {granted:N0} KB, Used {maxUsed:N0} KB",
-                Severity = PlanWarningSeverity.Warning
-            });
+                var grantedMB = granted / 1024.0;
+                var usedMB = maxUsed / 1024.0;
+                result.Add(new PlanWarning
+                {
+                    WarningType = "Memory Grant",
+                    Message = $"{kind}: Granted {grantedMB:N0} MB, Used {usedMB:N0} MB",
+                    Severity = PlanWarningSeverity.Warning
+                });
+            }
         }
 
         // Implicit conversions
diff --git a/tests/PlanViewer.Core.Tests/PlanAnalyzerTests.cs b/tests/PlanViewer.Core.Tests/PlanAnalyzerTests.cs
index 28ad002..33d0689 100644
--- a/tests/PlanViewer.Core.Tests/PlanAnalyzerTests.cs
+++ b/tests/PlanViewer.Core.Tests/PlanAnalyzerTests.cs
@@ -173,14 +173,15 @@ public void Rule08_ParallelSkew_DetectedOnHighRowScan()
     // ---------------------------------------------------------------
 
     [Fact]
-    public void Rule09a_ExcessiveMemoryGrant_DetectedInLazySpoolPlan()
+    public void Rule09a_ExcessiveMemoryGrant_SmallGrantSuppressed()
     {
+        // lazy_spool_plan has a 1 MB grant — well under the 1 GB threshold.
+        // The XML MemoryGrantWarning should be suppressed (not worth surfacing).
         var plan = PlanTestHelper.LoadAndAnalyze("lazy_spool_plan.sqlplan");
-        // The parser may surface this as a plan-level warning from XML
         var allWarnings = PlanTestHelper.AllWarnings(plan);
 
-        Assert.Contains(allWarnings, w =>
-            w.WarningType.Contains("Memory Grant") || w.WarningType == "Excessive Memory Grant");
+        Assert.DoesNotContain(allWarnings, w =>
+            w.WarningType == "Memory Grant");
     }
 
     // ---------------------------------------------------------------