range: build right range for NULL value on index column (#19385)

executor/executor_test.go

@@ -5658,6 +5658,38 @@ func (s *testSuite1) TestIssue16854(c *C) {
 	tk.MustExec("drop table t")
 }
 
+func (s *testSuite) TestIssue16921(c *C) {
+	tk := testkit.NewTestKitWithInit(c, s.store)
+
+	tk.MustExec("drop table if exists t;")
+	tk.MustExec("create table t (a float);")
+	tk.MustExec("create index a on t(a);")
+	tk.MustExec("insert into t values (1.0), (NULL), (0), (2.0);")
+	tk.MustQuery("select `a` from `t` use index (a) where !`a`;").Check(testkit.Rows("0"))
+	tk.MustQuery("select `a` from `t` ignore index (a) where !`a`;").Check(testkit.Rows("0"))
+	tk.MustQuery("select `a` from `t` use index (a) where `a`;").Check(testkit.Rows("1", "2"))
+	tk.MustQuery("select `a` from `t` ignore index (a) where `a`;").Check(testkit.Rows("1", "2"))
+	tk.MustQuery("select a from t use index (a) where not a is true;").Check(testkit.Rows("<nil>", "0"))
+	tk.MustQuery("select a from t use index (a) where not not a is true;").Check(testkit.Rows("1", "2"))
+	tk.MustQuery("select a from t use index (a) where not not a;").Check(testkit.Rows("1", "2"))
+	tk.MustQuery("select a from t use index (a) where not not not a is true;").Check(testkit.Rows("<nil>", "0"))
+	tk.MustQuery("select a from t use index (a) where not not not a;").Check(testkit.Rows("0"))
+}
+
+func (s *testSuite) TestIssue19100(c *C) {
+	tk := testkit.NewTestKitWithInit(c, s.store)
+
+	tk.MustExec("drop table if exists t1, t2;")
+	tk.MustExec("create table t1 (c decimal);")
+	tk.MustExec("create table t2 (c decimal, key(c));")
+	tk.MustExec("insert into t1 values (null);")
+	tk.MustExec("insert into t2 values (null);")
+	tk.MustQuery("select count(*) from t1 where not c;").Check(testkit.Rows("0"))
+	tk.MustQuery("select count(*) from t2 where not c;").Check(testkit.Rows("0"))
+	tk.MustQuery("select count(*) from t1 where c;").Check(testkit.Rows("0"))
+	tk.MustQuery("select count(*) from t2 where c;").Check(testkit.Rows("0"))
+}
+
 // this is from jira issue #5856
 func (s *testSuite1) TestInsertValuesWithSubQuery(c *C) {
 	tk := testkit.NewTestKit(c, s.store)

util/ranger/points.go

@@ -29,6 +29,7 @@ import (
 	"github.com/pingcap/tidb/types"
 	"github.com/pingcap/tidb/util/chunk"
 	"github.com/pingcap/tidb/util/collate"
+	"github.com/pingcap/tipb/go-tipb"
 )
 
 // Error instances.
@@ -312,8 +313,16 @@ func handleUnsignedIntCol(ft *types.FieldType, val types.Datum, op string) (type
 	return val, op, false
 }
 
-func (r *builder) buildFromIsTrue(expr *expression.ScalarFunction, isNot int) []point {
+func (r *builder) buildFromIsTrue(expr *expression.ScalarFunction, isNot int, keepNull bool) []point {
 	if isNot == 1 {
+		if keepNull {
+			// Range is {[0, 0]}
+			startPoint := point{start: true}
+			startPoint.value.SetInt64(0)
+			endPoint := point{}
+			endPoint.value.SetInt64(0)
+			return []point{startPoint, endPoint}
+		}
 		// NOT TRUE range is {[null null] [0, 0]}
 		startPoint1 := point{start: true}
 		endPoint1 := point{}
@@ -490,7 +499,8 @@ func (r *builder) newBuildFromPatternLike(expr *expression.ScalarFunction) []poi
 func (r *builder) buildFromNot(expr *expression.ScalarFunction) []point {
 	switch n := expr.FuncName.L; n {
 	case ast.IsTruth:
-		return r.buildFromIsTrue(expr, 1)
+		keepNull := r.isTrueKeepNull(expr)
+		return r.buildFromIsTrue(expr, 1, keepNull)
 	case ast.IsFalsity:
 		return r.buildFromIsFalse(expr, 1)
 	case ast.In:
@@ -546,7 +556,8 @@ func (r *builder) buildFromScalarFunc(expr *expression.ScalarFunction) []point {
 	case ast.LogicOr:
 		return r.union(r.build(expr.GetArgs()[0]), r.build(expr.GetArgs()[1]))
 	case ast.IsTruth:
-		return r.buildFromIsTrue(expr, 0)
+		keepNull := r.isTrueKeepNull(expr)
+		return r.buildFromIsTrue(expr, 0, keepNull)
 	case ast.IsFalsity:
 		return r.buildFromIsFalse(expr, 0)
 	case ast.In:
@@ -633,3 +644,11 @@ func (r *builder) merge(a, b []point, union bool) []point {
 	}
 	return mergedPoints[:curTail]
 }
+
+func (r *builder) isTrueKeepNull(expr *expression.ScalarFunction) bool {
+	switch expr.Function.PbCode() {
+	case tipb.ScalarFuncSig_DecimalIsTrueWithNull, tipb.ScalarFuncSig_RealIsTrueWithNull, tipb.ScalarFuncSig_IntIsTrueWithNull:
+		return true
+	}
+	return false
+}