expression: check if period is valid in period_add (pingcap#10380)

Author: qw4990

expression/builtin_time.go

@@ -4887,6 +4887,11 @@ func (c *periodAddFunctionClass) getFunction(ctx sessionctx.Context, args []Expr
 	return sig, nil
 }
 
+// validPeriod checks if this period is valid, it comes from MySQL 8.0+.
+func validPeriod(p int64) bool {
+	return !(p < 0 || p%100 == 0 || p%100 > 12)
+}
+
 // period2Month converts a period to months, in which period is represented in the format of YYMM or YYYYMM.
 // Note that the period argument is not a date value.
 func period2Month(period uint64) uint64 {
@@ -4938,15 +4943,16 @@ func (b *builtinPeriodAddSig) evalInt(row chunk.Row) (int64, bool, error) {
 		return 0, true, errors.Trace(err)
 	}
 
-	if p == 0 {
-		return 0, false, nil
-	}
-
 	n, isNull, err := b.args[1].EvalInt(b.ctx, row)
 	if isNull || err != nil {
 		return 0, true, errors.Trace(err)
 	}
 
+	// in MySQL, if p is invalid but n is NULL, the result is NULL, so we have to check if n is NULL first.
+	if !validPeriod(p) {
+		return 0, false, errIncorrectArgs.GenWithStackByArgs("period_add")
+	}
+
 	sumMonth := int64(period2Month(uint64(p))) + n
 	return int64(month2Period(uint64(sumMonth))), false, nil
 }

expression/builtin_time_test.go

@@ -2146,8 +2146,8 @@ func (s *testEvaluatorSuite) TestPeriodAdd(c *C) {
 		{201611, -13, true, 201510},
 		{1611, 3, true, 201702},
 		{7011, 3, true, 197102},
-		{12323, 10, true, 12509},
-		{0, 3, true, 0},
+		{12323, 10, false, 0},
+		{0, 3, false, 0},
 	}
 
 	fc := funcs[ast.PeriodAdd]

expression/integration_test.go

@@ -1438,10 +1438,16 @@ func (s *testIntegrationSuite) TestTimeBuiltin(c *C) {
 	result.Check(testkit.Rows("123456 10 <nil> <nil>"))
 
 	// for period_add
-	result = tk.MustQuery(`SELECT period_add(191, 2), period_add(191, -2), period_add(0, 20), period_add(0, 0);`)
-	result.Check(testkit.Rows("200809 200805 0 0"))
-	result = tk.MustQuery(`SELECT period_add(NULL, 2), period_add(-191, NULL), period_add(NULL, NULL), period_add(12.09, -2), period_add("21aa", "11aa"), period_add("", "");`)
-	result.Check(testkit.Rows("<nil> <nil> <nil> 200010 200208 0"))
+	result = tk.MustQuery(`SELECT period_add(200807, 2), period_add(200807, -2);`)
+	result.Check(testkit.Rows("200809 200805"))
+	result = tk.MustQuery(`SELECT period_add(NULL, 2), period_add(-191, NULL), period_add(NULL, NULL), period_add(12.09, -2), period_add("200207aa", "1aa");`)
+	result.Check(testkit.Rows("<nil> <nil> <nil> 200010 200208"))
+	for _, errPeriod := range []string{
+		"period_add(0, 20)", "period_add(0, 0)", "period_add(-1, 1)", "period_add(200013, 1)", "period_add(-200012, 1)", "period_add('', '')",
+	} {
+		err := tk.QueryToErr(fmt.Sprintf("SELECT %v;", errPeriod))
+		c.Assert(err.Error(), Equals, "[expression:1210]Incorrect arguments to period_add")
+	}
 
 	// for period_diff
 	result = tk.MustQuery(`SELECT period_diff(191, 2), period_diff(191, -2), period_diff(0, 0), period_diff(191, 191);`)