cherry pick #19259 to release-4.0 (#19403)

Signed-off-by: ti-srebot <ti-srebot@pingcap.com> Co-authored-by: Kenan Yao <cauchy1992@gmail.com>
pingcap · Aug 25, 2020 · 3f0740e · 3f0740e
1 parent 3fe0255
commit 3f0740e
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diff --git a/cmd/explaintest/r/explain_easy.result b/cmd/explaintest/r/explain_easy.result
@@ -772,3 +772,16 @@ label = "cop"
 }
 
 drop table if exists t;
+create table t(a binary(16) not null, b varchar(2) default null, c varchar(100) default 'aaaa', key (a,b));
+explain select * from t where a=x'FA34E1093CB428485734E3917F000000' and b='xb';
+id	estRows	task	access object	operator info
+IndexLookUp_10	0.10	root		
+├─IndexRangeScan_8(Build)	0.10	cop[tikv]	table:t, index:a(a, b)	range:["[250 52 225 9 60 180 40 72 87 52 227 145 127 0 0 0]" "xb","[250 52 225 9 60 180 40 72 87 52 227 145 127 0 0 0]" "xb"], keep order:false, stats:pseudo
+└─TableRowIDScan_9(Probe)	0.10	cop[tikv]	table:t	keep order:false, stats:pseudo
+explain update t set c = 'ssss' where a=x'FA34E1093CB428485734E3917F000000' and b='xb';
+id	estRows	task	access object	operator info
+Update_4	N/A	root		N/A
+└─IndexLookUp_11	0.10	root		
+  ├─IndexRangeScan_9(Build)	0.10	cop[tikv]	table:t, index:a(a, b)	range:["[250 52 225 9 60 180 40 72 87 52 227 145 127 0 0 0]" "xb","[250 52 225 9 60 180 40 72 87 52 227 145 127 0 0 0]" "xb"], keep order:false, stats:pseudo
+  └─TableRowIDScan_10(Probe)	0.10	cop[tikv]	table:t	keep order:false, stats:pseudo
+drop table if exists t;
diff --git a/cmd/explaintest/t/explain_easy.test b/cmd/explaintest/t/explain_easy.test
@@ -204,3 +204,9 @@ drop table if exists t;
 create table t(a int, b int);
 explain format="dot" select * from t where a < 2;
 drop table if exists t;
+
+# select / update should choose same access path for table t.
+create table t(a binary(16) not null, b varchar(2) default null, c varchar(100) default 'aaaa', key (a,b));
+explain select * from t where a=x'FA34E1093CB428485734E3917F000000' and b='xb';
+explain update t set c = 'ssss' where a=x'FA34E1093CB428485734E3917F000000' and b='xb';
+drop table if exists t;
diff --git a/types/datum.go b/types/datum.go
@@ -708,6 +708,10 @@ func (d *Datum) compareMysqlDecimal(sc *stmtctx.StatementContext, dec *MyDecimal
 
 func (d *Datum) compareMysqlDuration(sc *stmtctx.StatementContext, dur Duration) (int, error) {
 	switch d.k {
+	case KindNull, KindMinNotNull:
+		return -1, nil
+	case KindMaxValue:
+		return 1, nil
 	case KindMysqlDuration:
 		return d.GetMysqlDuration().Compare(dur), nil
 	case KindString, KindBytes:
@@ -720,6 +724,10 @@ func (d *Datum) compareMysqlDuration(sc *stmtctx.StatementContext, dur Duration)
 
 func (d *Datum) compareMysqlEnum(sc *stmtctx.StatementContext, enum Enum) (int, error) {
 	switch d.k {
+	case KindNull, KindMinNotNull:
+		return -1, nil
+	case KindMaxValue:
+		return 1, nil
 	case KindString, KindBytes, KindMysqlEnum, KindMysqlSet:
 		return CompareString(d.GetString(), enum.String(), d.collation), nil
 	default:
@@ -729,6 +737,10 @@ func (d *Datum) compareMysqlEnum(sc *stmtctx.StatementContext, enum Enum) (int,
 
 func (d *Datum) compareBinaryLiteral(sc *stmtctx.StatementContext, b BinaryLiteral) (int, error) {
 	switch d.k {
+	case KindNull, KindMinNotNull:
+		return -1, nil
+	case KindMaxValue:
+		return 1, nil
 	case KindString, KindBytes:
 		return CompareString(d.GetString(), b.ToString(), d.collation), nil
 	case KindBinaryLiteral, KindMysqlBit:
@@ -745,6 +757,10 @@ func (d *Datum) compareBinaryLiteral(sc *stmtctx.StatementContext, b BinaryLiter
 
 func (d *Datum) compareMysqlSet(sc *stmtctx.StatementContext, set Set) (int, error) {
 	switch d.k {
+	case KindNull, KindMinNotNull:
+		return -1, nil
+	case KindMaxValue:
+		return 1, nil
 	case KindString, KindBytes, KindMysqlEnum, KindMysqlSet:
 		return CompareString(d.GetString(), set.String(), d.collation), nil
 	default:
@@ -762,6 +778,10 @@ func (d *Datum) compareMysqlJSON(sc *stmtctx.StatementContext, target json.Binar
 
 func (d *Datum) compareMysqlTime(sc *stmtctx.StatementContext, time Time) (int, error) {
 	switch d.k {
+	case KindNull, KindMinNotNull:
+		return -1, nil
+	case KindMaxValue:
+		return 1, nil
 	case KindString, KindBytes:
 		dt, err := ParseDatetime(sc, d.GetString())
 		return dt.Compare(time), errors.Trace(err)