Merge pull request #342 from erikdarlingdata/fix/rule8-skew-thresholds

erikdarlingdata · web-flow · commit 608c1fdf7512 · 2026-02-27T06:04:09.000-05:00
Rule 8: Lower parallel skew thresholds, remove 4-thread minimum
diff --git a/Dashboard/Services/PlanAnalyzer.cs b/Dashboard/Services/PlanAnalyzer.cs
@@ -304,7 +304,8 @@ private static void AnalyzeNode(PlanNode node, PlanStatement stmt)
             {
                 var maxThread = node.PerThreadStats.OrderByDescending(t => t.ActualRows).First();
                 var skewRatio = (double)maxThread.ActualRows / totalRows;
-                if (skewRatio >= 0.9 && node.PerThreadStats.Count >= 4)
+                var skewThreshold = node.PerThreadStats.Count == 2 ? 0.75 : 0.50;
+                if (skewRatio >= skewThreshold)
                 {
                     node.Warnings.Add(new PlanWarning
                     {
diff --git a/Lite/Services/PlanAnalyzer.cs b/Lite/Services/PlanAnalyzer.cs
@@ -304,7 +304,8 @@ private static void AnalyzeNode(PlanNode node, PlanStatement stmt)
             {
                 var maxThread = node.PerThreadStats.OrderByDescending(t => t.ActualRows).First();
                 var skewRatio = (double)maxThread.ActualRows / totalRows;
-                if (skewRatio >= 0.9 && node.PerThreadStats.Count >= 4)
+                var skewThreshold = node.PerThreadStats.Count == 2 ? 0.75 : 0.50;
+                if (skewRatio >= skewThreshold)
                 {
                     node.Warnings.Add(new PlanWarning
                     {

Original file line number	Diff line number	Diff line change
`@@ -304,7 +304,8 @@ private static void AnalyzeNode(PlanNode node, PlanStatement stmt)`
`304`	`304`	`{`
`305`	`305`	`var maxThread = node.PerThreadStats.OrderByDescending(t => t.ActualRows).First();`
`306`	`306`	`var skewRatio = (double)maxThread.ActualRows / totalRows;`
`307`		`- if (skewRatio >= 0.9 && node.PerThreadStats.Count >= 4)`
	`307`	`+ var skewThreshold = node.PerThreadStats.Count == 2 ? 0.75 : 0.50;`
	`308`	`+ if (skewRatio >= skewThreshold)`
`308`	`309`	`{`
`309`	`310`	`node.Warnings.Add(new PlanWarning`
`310`	`311`	`{`