https://clickhouse.com/docs/en/sql-reference/statements/create/dictionary/

```
CREATE DICTIONARY [IF NOT EXISTS] [db.]dictionary_name [ON CLUSTER cluster]
(
    key1 type1  [DEFAULT|EXPRESSION expr1] [HIERARCHICAL|INJECTIVE|IS_OBJECT_ID],
    key2 type2  [DEFAULT|EXPRESSION expr2] [HIERARCHICAL|INJECTIVE|IS_OBJECT_ID],
    attr1 type2 [DEFAULT|EXPRESSION expr3],
    attr2 type2 [DEFAULT|EXPRESSION expr4]

```

`[HIERARCHICAL|INJECTIVE|IS_OBJECT_ID]` -- about attr1 not key1. 
And what is `IS_OBJECT_ID` ?
#include "DictionaryStructure.h"
#include <Columns/IColumn.h>
#include <DataTypes/DataTypeFactory.h>
#include <DataTypes/DataTypeNullable.h>
#include <DataTypes/DataTypeArray.h>
#include <Functions/FunctionHelpers.h>
#include <Formats/FormatSettings.h>
#include <IO/WriteHelpers.h>
#include <IO/Operators.h>
#include <Common/StringUtils/StringUtils.h>
#include <numeric>
#include <unordered_map>
#include <unordered_set>
namespace DB
{
namespace ErrorCodes
{
    extern const int UNKNOWN_TYPE;
    extern const int TYPE_MISMATCH;
    extern const int BAD_ARGUMENTS;
}
namespace
{
DictionaryTypedSpecialAttribute makeDictionaryTypedSpecialAttribute(