From e32aba0d7035d69bde0090eb09535aafca4403e2 Mon Sep 17 00:00:00 2001
From: SeaRise <846579815@qq.com>
Date: Mon, 23 Mar 2020 20:29:32 -0500
Subject: [PATCH] planner: implement BuildKeyInfo of LogicalTopN and
 LogicalTableDual (#15543)

---
 planner/core/rule_build_key_info.go              | 16 ++++++++++++++++
 .../core/testdata/plan_suite_unexported_out.json |  2 +-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/planner/core/rule_build_key_info.go b/planner/core/rule_build_key_info.go
index 1ec83ed113..aaf9de1efc 100644
--- a/planner/core/rule_build_key_info.go
+++ b/planner/core/rule_build_key_info.go
@@ -111,6 +111,22 @@ func (p *LogicalLimit) BuildKeyInfo(selfSchema *expression.Schema, childSchema [
 	}
 }
 
+// BuildKeyInfo implements LogicalPlan BuildKeyInfo interface.
+func (p *LogicalTopN) BuildKeyInfo(selfSchema *expression.Schema, childSchema []*expression.Schema) {
+	p.baseLogicalPlan.BuildKeyInfo(selfSchema, childSchema)
+	if p.Count == 1 {
+		p.maxOneRow = true
+	}
+}
+
+// BuildKeyInfo implements LogicalPlan BuildKeyInfo interface.
+func (p *LogicalTableDual) BuildKeyInfo(selfSchema *expression.Schema, childSchema []*expression.Schema) {
+	p.baseLogicalPlan.BuildKeyInfo(selfSchema, childSchema)
+	if p.RowCount == 1 {
+		p.maxOneRow = true
+	}
+}
+
 // A bijection exists between columns of a projection's schema and this projection's Exprs.
 // Sometimes we need a schema made by expr of Exprs to convert a column in child's schema to a column in this projection's Schema.
 func (p *LogicalProjection) buildSchemaByExprs(selfSchema *expression.Schema) *expression.Schema {
diff --git a/planner/core/testdata/plan_suite_unexported_out.json b/planner/core/testdata/plan_suite_unexported_out.json
index 567486bedb..6afb5519c3 100644
--- a/planner/core/testdata/plan_suite_unexported_out.json
+++ b/planner/core/testdata/plan_suite_unexported_out.json
@@ -169,7 +169,7 @@
         "Err": false
       },
       {
-        "Best": "Apply{UnionAll{UnionAll{Dual->Projection->Dual->Projection}->Aggr(firstrow(Column#4))->Projection->Dual->Projection}->Dual->Projection->MaxOneRow}->Sort->Projection",
+        "Best": "Join{UnionAll{UnionAll{Dual->Projection->Dual->Projection}->Aggr(firstrow(Column#4))->Projection->Dual->Projection}->Dual}->Sort->Projection",
         "Err": false
       }
     ]