planner: set right null flag for constant value (#23172)

pingcap · Mar 12, 2021 · 920b70d · 920b70d
1 parent 1e2f1c0
commit 920b70d
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Showing 7 changed files with 138 additions and 121 deletions.
diff --git a/cmd/explaintest/r/explain.result b/cmd/explaintest/r/explain.result
@@ -43,4 +43,4 @@ drop view if exists v;
 create view v as select cast(replace(substring_index(substring_index("",',',1),':',-1),'"','') as CHAR(32)) as event_id;
 desc v;
 Field	Type	Null	Key	Default	Extra
-event_id	varchar(32)	YES		NULL	
+event_id	varchar(32)	NO		NULL	
diff --git a/cmd/explaintest/r/explain_easy.result b/cmd/explaintest/r/explain_easy.result
@@ -613,14 +613,15 @@ HashJoin	8002.00	root		right outer join, equal:[eq(test.t.nb, test.t.nb)]
 explain format = 'brief' select ifnull(t.a, 1) in (select count(*) from t s , t t1 where s.a = t.a and s.a = t1.a) from t;
 id	estRows	task	access object	operator info
 Projection	10000.00	root		Column#14
-└─Apply	10000.00	root		CARTESIAN left outer semi join, other cond:eq(ifnull(test.t.a, 1), Column#13)
-  ├─TableReader(Build)	10000.00	root		data:TableFullScan
-  │ └─TableFullScan	10000.00	cop[tikv]	table:t	keep order:false, stats:pseudo
-  └─HashAgg(Probe)	1.00	root		funcs:count(Column#15)->Column#13
+└─Apply	10000.00	root		left outer semi join, equal:[eq(Column#15, Column#13)]
+  ├─Projection(Build)	10000.00	root		test.t.a, ifnull(test.t.a, 1)->Column#15
+  │ └─TableReader	10000.00	root		data:TableFullScan
+  │   └─TableFullScan	10000.00	cop[tikv]	table:t	keep order:false, stats:pseudo
+  └─HashAgg(Probe)	1.00	root		funcs:count(Column#17)->Column#13
     └─HashJoin	9.99	root		inner join, equal:[eq(test.t.a, test.t.a)]
-      ├─HashAgg(Build)	7.99	root		group by:test.t.a, funcs:count(Column#16)->Column#15, funcs:firstrow(test.t.a)->test.t.a
+      ├─HashAgg(Build)	7.99	root		group by:test.t.a, funcs:count(Column#18)->Column#17, funcs:firstrow(test.t.a)->test.t.a
       │ └─TableReader	7.99	root		data:HashAgg
-      │   └─HashAgg	7.99	cop[tikv]		group by:test.t.a, funcs:count(1)->Column#16
+      │   └─HashAgg	7.99	cop[tikv]		group by:test.t.a, funcs:count(1)->Column#18
       │     └─Selection	9.99	cop[tikv]		eq(test.t.a, test.t.a), not(isnull(test.t.a))
       │       └─TableFullScan	10000.00	cop[tikv]	table:t1	keep order:false, stats:pseudo
       └─TableReader(Probe)	9.99	root		data:Selection

diff --git a/expression/constant_fold.go b/expression/constant_fold.go
@@ -16,6 +16,7 @@ package expression
 import (
 	"github.com/pingcap/parser/ast"
 	"github.com/pingcap/parser/mysql"
+	"github.com/pingcap/tidb/types"
 	"github.com/pingcap/tidb/util/chunk"
 	"github.com/pingcap/tidb/util/logutil"
 	"go.uber.org/zap"
@@ -207,14 +208,24 @@ func foldConstant(expr Expression) (Expression, bool) {
 			return expr, isDeferredConst
 		}
 		value, err := x.Eval(chunk.Row{})
+		retType := x.RetType.Clone()
+		if !hasNullArg {
+			// set right not null flag for constant value
+			switch value.Kind() {
+			case types.KindNull:
+				retType.Flag &= ^mysql.NotNullFlag
+			default:
+				retType.Flag |= mysql.NotNullFlag
+			}
+		}
 		if err != nil {
 			logutil.BgLogger().Debug("fold expression to constant", zap.String("expression", x.ExplainInfo()), zap.Error(err))
 			return expr, isDeferredConst
 		}
 		if isDeferredConst {
-			return &Constant{Value: value, RetType: x.RetType, DeferredExpr: x}, true
+			return &Constant{Value: value, RetType: retType, DeferredExpr: x}, true
 		}
-		return &Constant{Value: value, RetType: x.RetType}, false
+		return &Constant{Value: value, RetType: retType}, false
 	case *Constant:
 		if x.ParamMarker != nil {
 			return &Constant{

diff --git a/expression/expr_to_pb.go b/expression/expr_to_pb.go
@@ -64,9 +64,6 @@ func (pc PbConverter) ExprToPB(expr Expression) *tipb.Expr {
 		if pbExpr == nil {
 			return nil
 		}
-		if !x.Value.IsNull() {
-			pbExpr.FieldType.Flag |= uint32(mysql.NotNullFlag)
-		}
 		return pbExpr
 	case *CorrelatedColumn:
 		return pc.conOrCorColToPBExpr(expr)

diff --git a/expression/expr_to_pb_test.go b/expression/expr_to_pb_test.go
@@ -270,6 +270,7 @@ func (s *testEvaluatorSuite) TestLikeFunc2Pb(c *C) {
 	client := new(mock.Client)
 
 	retTp := types.NewFieldType(mysql.TypeString)
+	retTp.Flag |= mysql.NotNullFlag
 	retTp.Charset = charset.CharsetUTF8
 	retTp.Collate = charset.CollationUTF8
 	args := []Expression{