planner: Set minimum cost to avoid parent multiplication cost discrep…

…ancies (#56387) (#56411) ref #55126
pingcap · Nov 12, 2024 · 2709f89 · 2709f89
1 parent a0fdddb
commit 2709f89
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Showing 3 changed files with 10 additions and 10 deletions.
diff --git a/planner/core/casetest/testdata/plan_normalized_suite_out.json b/planner/core/casetest/testdata/plan_normalized_suite_out.json
@@ -417,17 +417,17 @@
           " TableReader           root         ",
           " └─ExchangeSender      cop[tiflash] ",
           "   └─Projection        cop[tiflash] test.t1.a",
-          "     └─Selection       cop[tiflash] gt(test.t1.b, ?)",
-          "       └─TableFullScan cop[tiflash] table:t1, range:[?,?], pushed down filter:gt(test.t1.a, ?), keep order:false"
+          "     └─Selection       cop[tiflash] gt(test.t1.a, ?)",
+          "       └─TableFullScan cop[tiflash] table:t1, range:[?,?], pushed down filter:gt(test.t1.b, ?), keep order:false"
         ]
       },
       {
         "SQL": "explain select * from t1 where a>1 and b>1 and c>1",
         "Plan": [
           " TableReader         root         ",
           " └─ExchangeSender    cop[tiflash] ",
-          "   └─Selection       cop[tiflash] gt(test.t1.b, ?)",
-          "     └─TableFullScan cop[tiflash] table:t1, range:[?,?], pushed down filter:gt(test.t1.a, ?), gt(test.t1.c, ?), keep order:false"
+          "   └─Selection       cop[tiflash] gt(test.t1.c, ?)",
+          "     └─TableFullScan cop[tiflash] table:t1, range:[?,?], pushed down filter:gt(test.t1.a, ?), gt(test.t1.b, ?), keep order:false"
         ]
       },
       {
@@ -443,8 +443,8 @@
         "Plan": [
           " TableReader         root         ",
           " └─ExchangeSender    cop[tiflash] ",
-          "   └─Selection       cop[tiflash] gt(test.t1.b, ?), or(lt(test.t1.a, ?), lt(test.t1.b, ?))",
-          "     └─TableFullScan cop[tiflash] table:t1, range:[?,?], pushed down filter:gt(test.t1.a, ?), keep order:false"
+          "   └─Selection       cop[tiflash] gt(test.t1.a, ?), or(lt(test.t1.a, ?), lt(test.t1.b, ?))",
+          "     └─TableFullScan cop[tiflash] table:t1, range:[?,?], pushed down filter:gt(test.t1.b, ?), keep order:false"
         ]
       },
       {

diff --git a/planner/core/plan_cost_ver2.go b/planner/core/plan_cost_ver2.go
@@ -759,7 +759,7 @@ func scanCostVer2(option *PlanCostOption, rows, rowSize float64, scanFactor cost
 	}
 	return newCostVer2(option, scanFactor,
 		// rows * log(row-size) * scanFactor, log2 from experiments
-		rows*math.Log2(rowSize)*scanFactor.Value,
+		rows*math.Max(math.Log2(rowSize), 0)*scanFactor.Value,
 		func() string { return fmt.Sprintf("scan(%v*logrowsize(%v)*%v)", rows, rowSize, scanFactor) })
 }
 
@@ -1046,7 +1046,7 @@ func sumCostVer2(costs ...costVer2) (ret costVer2) {
 		return
 	}
 	for i, c := range costs {
-		ret.cost += c.cost
+		ret.cost += math.Max(c.cost, 0)
 		if c.trace != nil {
 			if i == 0 { // init
 				ret.trace = &costTrace{make(map[string]float64), ""}

diff --git a/planner/core/task.go b/planner/core/task.go
@@ -309,11 +309,11 @@ func (p *PhysicalIndexJoin) attach2Task(tasks ...task) task {
 
 func getAvgRowSize(stats *property.StatsInfo, cols []*expression.Column) (size float64) {
 	if stats.HistColl != nil {
-		size = stats.HistColl.GetAvgRowSizeListInDisk(cols)
+		size = math.Max(stats.HistColl.GetAvgRowSizeListInDisk(cols), 0)
 	} else {
 		// Estimate using just the type info.
 		for _, col := range cols {
-			size += float64(chunk.EstimateTypeWidth(col.GetType()))
+			size += math.Max(float64(chunk.EstimateTypeWidth(col.GetType())), 0)
 		}
 	}
 	return