implement rounding behavior

Author: James Cor

sql/columndefault.go

@@ -82,9 +82,15 @@ func (e *ColumnDefaultValue) Eval(ctx *Context, r Row) (interface{}, error) {
 
 	if e.OutType != nil {
 		var inRange ConvertInRange
-		if val, inRange, err = e.OutType.Convert(ctx, val); err != nil {
+		if roundType, isRoundType := e.OutType.(RoundingNumberType); isRoundType {
+			val, inRange, err = roundType.ConvertRound(ctx, val)
+		} else {
+			val, inRange, err = e.OutType.Convert(ctx, val)
+		}
+		if err != nil {
 			return nil, ErrIncompatibleDefaultType.New()
-		} else if !inRange {
+		}
+		if !inRange {
 			return nil, ErrValueOutOfRange.New(val, e.OutType)
 		}
 	}
@@ -227,13 +233,19 @@ func (e *ColumnDefaultValue) CheckType(ctx *Context) error {
 		if val == nil && !e.ReturnNil {
 			return ErrIncompatibleDefaultType.New()
 		}
-		_, inRange, err := e.OutType.Convert(ctx, val)
+		// TODO: ColumnDefaultValue.Eval() has the same chunk of code; use helper method?
+		var inRange ConvertInRange
+		if roundType, isRoundType := e.OutType.(RoundingNumberType); isRoundType {
+			val, inRange, err = roundType.ConvertRound(ctx, val)
+		} else {
+			val, inRange, err = e.OutType.Convert(ctx, val)
+		}
 		if err != nil {
 			return ErrIncompatibleDefaultType.Wrap(err)
-		} else if !inRange {
+		}
+		if !inRange {
 			return ErrIncompatibleDefaultType.Wrap(ErrValueOutOfRange.New(val, e.Expr))
 		}
-
 	}
 	return nil
 }

sql/rowexec/insert.go

@@ -122,7 +122,14 @@ func (i *insertIter) Next(ctx *sql.Context) (returnRow sql.Row, returnErr error)
 			ctxWithColumnInfo := ctx.WithContext(ctxWithValues)
 			val := row[idx]
 			// TODO: check mysql strict sql_mode
-			converted, inRange, cErr := col.Type.Convert(ctxWithColumnInfo, val)
+			var converted any
+			var inRange sql.ConvertInRange
+			var cErr error
+			if typ, ok := col.Type.(sql.RoundingNumberType); ok {
+				converted, inRange, cErr = typ.ConvertRound(ctx, val)
+			} else {
+				converted, inRange, cErr = col.Type.Convert(ctxWithColumnInfo, val)
+			}
 			if cErr == nil && !inRange {
 				cErr = sql.ErrValueOutOfRange.New(val, col.Type)
 			}

sql/type.go

@@ -128,6 +128,13 @@ type NumberType interface {
 	DisplayWidth() int
 }
 
+// RoundingNumberType represents Number Types that implement an additional interface
+// that supports rounding when converting rather than the default truncation.
+type RoundingNumberType interface {
+	NumberType
+	ConvertRound(context.Context, any) (any, ConvertInRange, error)
+}
+
 // StringType represents all string types, including VARCHAR and BLOB.
 // https://dev.mysql.com/doc/refman/8.0/en/char.html
 // https://dev.mysql.com/doc/refman/8.0/en/binary-varbinary.html