expression: throw "too big precision" error for CAST(AS TIME)

expression/builtin_cast.go

@@ -1001,7 +1001,7 @@ func (b *builtinCastDecimalAsDurationSig) Clone() builtinFunc {
 func (b *builtinCastDecimalAsDurationSig) evalDuration(row chunk.Row) (res types.Duration, isNull bool, err error) {
 	val, isNull, err := b.args[0].EvalDecimal(b.ctx, row)
 	if isNull || err != nil {
-		return res, false, err
+		return res, true, err
 	}
 	res, err = types.ParseDuration(b.ctx.GetSessionVars().StmtCtx, string(val.ToString()), b.tp.Decimal)
 	if types.ErrTruncatedWrongVal.Equal(err) {

expression/integration_test.go

@@ -3797,3 +3797,33 @@ func (s *testIntegrationSuite) TestUserVarMockWindFunc(c *C) {
 		`3 6 3 key3-value6 insert_order6`,
 	))
 }
+
+func (s *testIntegrationSuite) TestCastAsTime(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec(`use test;`)
+	tk.MustExec(`drop table if exists t;`)
+	tk.MustExec(`create table t (col1 bigint, col2 double, col3 decimal, col4 varchar(20), col5 json);`)
+	tk.MustExec(`insert into t values (1, 1, 1, "1", "1");`)
+	tk.MustExec(`insert into t values (null, null, null, null, null);`)
+	tk.MustQuery(`select cast(col1 as time), cast(col2 as time), cast(col3 as time), cast(col4 as time), cast(col5 as time) from t where col1 = 1;`).Check(testkit.Rows(
+		`00:00:01 00:00:01 00:00:01 00:00:01 00:00:01`,
+	))
+	tk.MustQuery(`select cast(col1 as time), cast(col2 as time), cast(col3 as time), cast(col4 as time), cast(col5 as time) from t where col1 is null;`).Check(testkit.Rows(
+		`<nil> <nil> <nil> <nil> <nil>`,
+	))
+
+	err := tk.ExecToErr(`select cast(col1 as time(31)) from t where col1 is null;`)
+	c.Assert(err.Error(), Equals, "[expression:1426]Too big precision 31 specified for column 'CAST'. Maximum is 6.")
+
+	err = tk.ExecToErr(`select cast(col2 as time(31)) from t where col1 is null;`)
+	c.Assert(err.Error(), Equals, "[expression:1426]Too big precision 31 specified for column 'CAST'. Maximum is 6.")
+
+	err = tk.ExecToErr(`select cast(col3 as time(31)) from t where col1 is null;`)
+	c.Assert(err.Error(), Equals, "[expression:1426]Too big precision 31 specified for column 'CAST'. Maximum is 6.")
+
+	err = tk.ExecToErr(`select cast(col4 as time(31)) from t where col1 is null;`)
+	c.Assert(err.Error(), Equals, "[expression:1426]Too big precision 31 specified for column 'CAST'. Maximum is 6.")
+
+	err = tk.ExecToErr(`select cast(col5 as time(31)) from t where col1 is null;`)
+	c.Assert(err.Error(), Equals, "[expression:1426]Too big precision 31 specified for column 'CAST'. Maximum is 6.")
+}

planner/core/errors.go

@@ -60,6 +60,7 @@ const (
 	codeWindowNoInherentFrame           = mysql.ErrWindowNoInherentFrame
 	codeWindowNoRedefineOrderBy         = mysql.ErrWindowNoRedefineOrderBy
 	codeWindowDuplicateName             = mysql.ErrWindowDuplicateName
+	codeErrTooBigPrecision              = mysql.ErrTooBigPrecision
 )
 
 // error definitions.
@@ -106,6 +107,7 @@ var (
 	ErrWindowNoInherentFrame           = terror.ClassOptimizer.New(codeWindowNoInherentFrame, mysql.MySQLErrName[mysql.ErrWindowNoInherentFrame])
 	ErrWindowNoRedefineOrderBy         = terror.ClassOptimizer.New(codeWindowNoRedefineOrderBy, mysql.MySQLErrName[mysql.ErrWindowNoRedefineOrderBy])
 	ErrWindowDuplicateName             = terror.ClassOptimizer.New(codeWindowDuplicateName, mysql.MySQLErrName[mysql.ErrWindowDuplicateName])
+	errTooBigPrecision                 = terror.ClassExpression.New(mysql.ErrTooBigPrecision, mysql.MySQLErrName[mysql.ErrTooBigPrecision])
 )
 
 func init() {
@@ -142,6 +144,7 @@ func init() {
 		codeWindowNoInherentFrame:           mysql.ErrWindowNoInherentFrame,
 		codeWindowNoRedefineOrderBy:         mysql.ErrWindowNoRedefineOrderBy,
 		codeWindowDuplicateName:             mysql.ErrWindowDuplicateName,
+		codeErrTooBigPrecision:              mysql.ErrTooBigPrecision,
 	}
 	terror.ErrClassToMySQLCodes[terror.ClassOptimizer] = mysqlErrCodeMap
 }

planner/core/expression_rewriter.go

@@ -793,10 +793,18 @@ func (er *expressionRewriter) Leave(originInNode ast.Node) (retNode ast.Node, ok
 		er.caseToExpression(v)
 	case *ast.FuncCastExpr:
 		arg := er.ctxStack[len(er.ctxStack)-1]
+
 		er.err = expression.CheckArgsNotMultiColumnRow(arg)
 		if er.err != nil {
 			return retNode, false
 		}
+
+		// check the decimal precision of "CAST(AS TIME)".
+		er.err = er.checkTimePrecision(v.Tp)
+		if er.err != nil {
+			return retNode, false
+		}
+
 		er.ctxStack[len(er.ctxStack)-1] = expression.BuildCastFunction(er.ctx, arg, v.Tp)
 	case *ast.PatternLikeExpr:
 		er.likeToScalarFunc(v)
@@ -827,6 +835,13 @@ func (er *expressionRewriter) Leave(originInNode ast.Node) (retNode ast.Node, ok
 	return originInNode, true
 }
 
+func (er *expressionRewriter) checkTimePrecision(ft *types.FieldType) error {
+	if ft.EvalType() == types.ETDuration && ft.Decimal > types.MaxFsp {
+		return errTooBigPrecision.GenWithStackByArgs(ft.Decimal, "CAST", types.MaxFsp)
+	}
+	return nil
+}
+
 func (er *expressionRewriter) useCache() bool {
 	return er.ctx.GetSessionVars().StmtCtx.UseCache
 }