From 2b2f226309ee41c30913d05303212eeee3ff3b45 Mon Sep 17 00:00:00 2001
From: justarandomstring <847426363@qq.com>
Date: Tue, 15 Oct 2019 01:42:30 +0800
Subject: [PATCH 1/3] add a test for left outer join

---
 planner/core/physical_plan_test.go        | 37 +++++++++++++++++++++++
 planner/core/testdata/plan_suite_in.json  |  6 ++++
 planner/core/testdata/plan_suite_out.json |  9 ++++++
 3 files changed, 52 insertions(+)

diff --git a/planner/core/physical_plan_test.go b/planner/core/physical_plan_test.go
index bba9dcb22f576..17e0e0e069f0b 100644
--- a/planner/core/physical_plan_test.go
+++ b/planner/core/physical_plan_test.go
@@ -1073,3 +1073,40 @@ func testDAGPlanBuilderSplitAvg(c *C, root core.PhysicalPlan) {
 		testDAGPlanBuilderSplitAvg(c, son)
 	}
 }
+
+func (s *testPlanSuite) TestSimplifyOuterJoinWithCast(c *C) {
+	defer testleak.AfterTest(c)()
+	store, dom, err := newStoreWithBootstrap()
+	c.Assert(err, IsNil)
+	defer func() {
+		dom.Close()
+		store.Close()
+	}()
+	se, err := session.CreateSession4Test(store)
+	c.Assert(err, IsNil)
+	_, err = se.Execute(context.Background(), "use test")
+	c.Assert(err, IsNil)
+
+	var input []string
+	var output []struct {
+		SQL  string
+		Best string
+	}
+	s.testData.GetTestCases(c, &input, &output)
+	for i, test := range input {
+		comment := Commentf("case:%v sql:%s", i, test)
+		stmt, err := s.ParseOneStmt(test, "", "")
+		c.Assert(err, IsNil, comment)
+
+		p, err := planner.Optimize(context.Background(), se, stmt, s.is)
+		c.Assert(err, IsNil)
+		s.testData.OnRecord(func() {
+			output[i].SQL = test
+			output[i].Best = core.ToString(p)
+		})
+		c.Assert(core.ToString(p), Equals, output[i].Best)
+
+		warnings := se.GetSessionVars().StmtCtx.GetWarnings()
+		c.Assert(warnings, HasLen, 0, comment)
+	}
+}
diff --git a/planner/core/testdata/plan_suite_in.json b/planner/core/testdata/plan_suite_in.json
index 55a6d826fad64..6c4fcbae7c956 100644
--- a/planner/core/testdata/plan_suite_in.json
+++ b/planner/core/testdata/plan_suite_in.json
@@ -481,5 +481,11 @@
     "cases": [
       "select t1.a, (select count(t2.a) from t t2 where t2.g in (select t3.d from t t3 where t3.c = t1.a)) as agg_col from t t1;"
     ]
+  },
+  {
+    "name": "TestSimplifyOuterJoinWithCast",
+    "cases": [
+      "select * from t t1 left join t t2 on t1.a = t2.a where cast(t1.c_str as float) = '2.3'"
+    ]
   }
 ]
diff --git a/planner/core/testdata/plan_suite_out.json b/planner/core/testdata/plan_suite_out.json
index 011f2a8f49524..420dcc7b9253c 100644
--- a/planner/core/testdata/plan_suite_out.json
+++ b/planner/core/testdata/plan_suite_out.json
@@ -1241,5 +1241,14 @@
         "Best": "Apply{IndexReader(Index(t.f)[[NULL,+inf]])->IndexMergeJoin{IndexReader(Index(t.c_d_e)[[NULL,+inf]]->HashAgg)->HashAgg->IndexReader(Index(t.g)[[NULL,+inf]])}(Column#29,Column#23)}->HashAgg"
       }
     ]
+  },
+  {
+    "Name": "TestSimplifyOuterJoinWithCast",
+    "Cases": [
+      {
+        "SQL": "select * from t t1 left join t t2 on t1.a = t2.a where cast(t1.c_str as float) = '2.3'",
+        "Best": "MergeLeftOuterJoin{TableReader(Table(t))->Sel([eq(cast(Column#6), 2.3)])->TableReader(Table(t))}(Column#1,Column#13)"
+      }
+    ]
   }
 ]

From fb0ecee8b47a374399d18cb5c6aea6d3dd21ddf7 Mon Sep 17 00:00:00 2001
From: justarandomstring <847426363@qq.com>
Date: Tue, 15 Oct 2019 01:55:13 +0800
Subject: [PATCH 2/3] fix simplify outer join

---
 expression/expression.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/expression/expression.go b/expression/expression.go
index 67c002622c192..5332a11c9e930 100644
--- a/expression/expression.go
+++ b/expression/expression.go
@@ -542,6 +542,9 @@ func EvaluateExprWithNull(ctx sessionctx.Context, schema *Schema, expr Expressio
 		for i, arg := range x.GetArgs() {
 			args[i] = EvaluateExprWithNull(ctx, schema, arg)
 		}
+		if x.FuncName.L == ast.Cast {
+			return NewFunctionInternal(ctx, x.FuncName.L, x.RetType, args...)
+		}
 		return NewFunctionInternal(ctx, x.FuncName.L, types.NewFieldType(mysql.TypeTiny), args...)
 	case *Column:
 		if !schema.Contains(x) {

From ef000f45f3daf9f5744346aeba168406725cc27a Mon Sep 17 00:00:00 2001
From: justarandomstring <847426363@qq.com>
Date: Tue, 15 Oct 2019 15:59:15 +0800
Subject: [PATCH 3/3] simplify the logic

---
 expression/expression.go | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/expression/expression.go b/expression/expression.go
index 5332a11c9e930..b1d0345cfa0e8 100644
--- a/expression/expression.go
+++ b/expression/expression.go
@@ -542,10 +542,7 @@ func EvaluateExprWithNull(ctx sessionctx.Context, schema *Schema, expr Expressio
 		for i, arg := range x.GetArgs() {
 			args[i] = EvaluateExprWithNull(ctx, schema, arg)
 		}
-		if x.FuncName.L == ast.Cast {
-			return NewFunctionInternal(ctx, x.FuncName.L, x.RetType, args...)
-		}
-		return NewFunctionInternal(ctx, x.FuncName.L, types.NewFieldType(mysql.TypeTiny), args...)
+		return NewFunctionInternal(ctx, x.FuncName.L, x.RetType, args...)
 	case *Column:
 		if !schema.Contains(x) {
 			return x