planner: refine range builder when meet unsigned_int_col <cmp> -int_cnst

util/ranger/points.go

@@ -250,6 +250,11 @@ func (r *builder) buildFormBinOp(expr *expression.ScalarFunction) []point {
 		return nil
 	}
 
+	value, op, isValidRange := handleUnsignedIntCol(ft, value, op)
+	if !isValidRange {
+		return nil
+	}
+
 	switch op {
 	case ast.EQ:
 		startPoint := point{value: value, start: true}
@@ -339,6 +344,29 @@ func HandlePadCharToFullLength(sc *stmtctx.StatementContext, ft *types.FieldType
 	}
 }
 
+// handleUnsignedIntCol handles the case when unsigned column meets negative integer value.
+// The three returned values are: fixed constant value, fixed operator, and a boolean
+// which indicates whether the range is valid or not.
+func handleUnsignedIntCol(ft *types.FieldType, val types.Datum, op string) (types.Datum, string, bool) {
+	isUnsigned := mysql.HasUnsignedFlag(ft.Flag)
+	isIntegerType := mysql.IsIntegerType(ft.Tp)
+	isNegativeInteger := (val.Kind() == types.KindInt64 && val.GetInt64() < 0)
+
+	if !isUnsigned || !isIntegerType || !isNegativeInteger {
+		return val, op, true
+	}
+
+	// If the operator is GT, GE or NE, the range should be [0, +inf].
+	// Otherwise the value is out of valid range.
+	if op == ast.GT || op == ast.GE || op == ast.NE {
+		op = ast.GE
+		val.SetUint64(0)
+		return val, op, true
+	}
+
+	return val, op, false
+}
+
 func (r *builder) buildFromIsTrue(expr *expression.ScalarFunction, isNot int) []point {
 	if isNot == 1 {
 		// NOT TRUE range is {[null null] [0, 0]}

util/ranger/ranger_test.go

@@ -660,6 +660,39 @@ func (s *testRangerSuite) TestIndexRangeForUnsignedInt(c *C) {
 			filterConds: "[]",
 			resultStr:   `[(NULL,1) (2,9223372036854775810) (9223372036854775810,+inf]]`,
 		},
+		{
+			indexPos:    0,
+			exprStr:     `a >= -2147483648`,
+			accessConds: "[ge(test.t.a, -2147483648)]",
+			filterConds: "[]",
+			resultStr:   `[[0,+inf]]`,
+		},
+		{
+			indexPos:    0,
+			exprStr:     `a > -2147483648`,
+			accessConds: "[gt(test.t.a, -2147483648)]",
+			filterConds: "[]",
+			resultStr:   `[[0,+inf]]`,
+		},
+		{
+			indexPos:    0,
+			exprStr:     `a != -2147483648`,
+			accessConds: "[ne(test.t.a, -2147483648)]",
+			filterConds: "[]",
+			resultStr:   `[[0,+inf]]`,
+		},
+		{
+			exprStr:     "a < -1 or a < 1",
+			accessConds: "[or(lt(test.t.a, -1), lt(test.t.a, 1))]",
+			filterConds: "[]",
+			resultStr:   "[[-inf,1)]",
+		},
+		{
+			exprStr:     "a < -1 and a < 1",
+			accessConds: "[lt(test.t.a, -1) lt(test.t.a, 1)]",
+			filterConds: "[]",
+			resultStr:   "[]",
+		},
 	}
 
 	for _, tt := range tests {
@@ -933,6 +966,13 @@ func (s *testRangerSuite) TestColumnRange(c *C) {
 			filterConds: "[]",
 			resultStr:   "[(18446744073709500000,+inf]]",
 		},
+		{
+			colPos:      4,
+			exprStr:     `e > -2147483648`,
+			accessConds: "[gt(test.t.e, -2147483648)]",
+			filterConds: "[]",
+			resultStr:   "[[0,+inf]]",
+		},
 	}
 
 	for _, tt := range tests {