added TypeAwareConversion

Author: angelamayxie

enginetest/queries/script_queries.go

@@ -9393,7 +9393,6 @@ where
 		},
 	},
 	{
-		Skip:    true,
 		Name:    "set conversion to strings",
 		Dialect: "mysql",
 		SetUpScript: []string{
@@ -9429,6 +9428,7 @@ where
 				},
 			},
 			{
+				Skip:  true,
 				Query: "select s from t where s like 'a%' order by s;",
 				Expected: []sql.Row{
 					{"abc"},
@@ -9518,6 +9518,7 @@ where
 				},
 			},
 			{
+				Skip:  true,
 				Query: "select s, cast(s as char) from t order by s;",
 				Expected: []sql.Row{
 					{"abc", "abc"},
@@ -9526,6 +9527,7 @@ where
 				},
 			},
 			{
+				Skip:  true,
 				Query: "select s, cast(s as binary) from t order by s;",
 				Expected: []sql.Row{
 					{"abc", []uint8("abc")},

sql/expression/case.go

@@ -136,7 +136,7 @@ func (c *Case) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
 			}
 			// When unable to convert to the type of the case, return the original value
 			// A common error here is "Out of bounds value for decimal type"
-			if ret, _, err := t.Convert(ctx, bval); err == nil {
+			if ret, err := types.TypeAwareConversion(ctx, bval, b.Value.Type(), t); err == nil {
 				return ret, nil
 			}
 			return bval, nil
@@ -150,7 +150,7 @@ func (c *Case) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
 		}
 		// When unable to convert to the type of the case, return the original value
 		// A common error here is "Out of bounds value for decimal type"
-		if ret, _, err := t.Convert(ctx, val); err == nil {
+		if ret, err := types.TypeAwareConversion(ctx, val, c.Else.Type(), t); err == nil {
 			return ret, nil
 		}
 		return val, nil

sql/types/conversion.go

@@ -735,3 +735,17 @@ func GeneralizeTypes(a, b sql.Type) sql.Type {
 	// TODO: decide if we want to make this VarChar to match MySQL, match VarChar length to max of two types
 	return LongText
 }
+
+func TypeAwareConversion(ctx *sql.Context, val interface{}, originalType sql.Type, convertedType sql.Type) (interface{}, error) {
+	var converted interface{}
+	var err error
+	if IsTextOnly(convertedType) {
+		converted, _, err = ConvertToCollatedString(ctx, val, originalType)
+	} else {
+		converted, _, err = convertedType.Convert(ctx, val)
+	}
+	if err != nil {
+		return nil, err
+	}
+	return converted, nil
+}