fix CreateColumnFromAst

Author: 1261385937

clickhouse/columns/factory.cpp

@@ -137,12 +137,17 @@ static ColumnRef CreateColumnFromAst(const TypeAst& ast, CreateColumnByTypeSetti
 
         case TypeAst::Enum: {
             std::vector<Type::EnumItem> enum_items;
-
-            enum_items.reserve(ast.elements.size() / 2);
-            for (size_t i = 0; i < ast.elements.size(); i += 2) {
+            if (ast.elements.size() == 1) {
                 enum_items.push_back(
-                    Type::EnumItem{ast.elements[i].value_string,
-                                   (int16_t)ast.elements[i + 1].value});
+                    Type::EnumItem{ ast.elements[0].value_string, 0 });
+            }
+            else {
+                enum_items.reserve(ast.elements.size() / 2);
+                for (size_t i = 0; i < ast.elements.size(); i += 2) {
+                    enum_items.push_back(
+                        Type::EnumItem{ ast.elements[i].value_string,
+                                       (int16_t)ast.elements[i + 1].value });
+                }
             }
 
             if (ast.code == Type::Enum8) {