Revert "planner: fix the wrong cost formula of MPPExchanger" (#35707)

ref #35240
pingcap · Jun 24, 2022 · 3f8df8c · 3f8df8c
1 parent d0c1d1f
commit 3f8df8c
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Showing 5 changed files with 178 additions and 183 deletions.
diff --git a/executor/tiflashtest/tiflash_test.go b/executor/tiflashtest/tiflash_test.go
@@ -281,7 +281,7 @@ func TestMppExecution(t *testing.T) {
 	require.NoError(t, err)
 	ts := txn.StartTS()
 	taskID := tk.Session().GetSessionVars().AllocMPPTaskID(ts)
-	require.Equal(t, int64(5), taskID)
+	require.Equal(t, int64(6), taskID)
 	tk.MustExec("commit")
 	taskID = tk.Session().GetSessionVars().AllocMPPTaskID(ts + 1)
 	require.Equal(t, int64(1), taskID)

diff --git a/planner/core/plan_cost.go b/planner/core/plan_cost.go
@@ -1208,9 +1208,9 @@ func (p *PhysicalExchangeReceiver) GetPlanCost(taskType property.TaskType, costF
 		return 0, err
 	}
 	p.planCost = childCost
-	// accumulate net cost: rows * row-size * net-factor
-	rowSize := getTblStats(p.children[0]).GetAvgRowSize(p.ctx, p.children[0].Schema().Columns, false, false)
-	p.planCost += getCardinality(p.children[0], costFlag) * rowSize * p.ctx.GetSessionVars().GetNetworkFactor(nil)
+	// accumulate net cost
+	// TODO: this formula is wrong since it doesn't consider tableRowSize, fix it later
+	p.planCost += getCardinality(p.children[0], costFlag) * p.ctx.GetSessionVars().GetNetworkFactor(nil)
 	p.planCostInit = true
 	return p.planCost, nil
 }

diff --git a/planner/core/task.go b/planner/core/task.go
@@ -2070,8 +2070,7 @@ func (t *mppTask) enforceExchangerImpl(prop *property.PhysicalProperty) *mppTask
 	sender.SetChildren(t.p)
 	receiver := PhysicalExchangeReceiver{}.Init(ctx, t.p.statsInfo())
 	receiver.SetChildren(sender)
-	rowSize := getTblStats(sender.children[0]).GetAvgRowSize(sender.ctx, sender.children[0].Schema().Columns, false, false)
-	cst := t.cst + t.count()*rowSize*ctx.GetSessionVars().GetNetworkFactor(nil)
+	cst := t.cst + t.count()*ctx.GetSessionVars().GetNetworkFactor(nil)
 	sender.cost = cst
 	receiver.cost = cst
 	return &mppTask{