I have a table with one million rows of data. And It's schema is like:
```
create table redis_dictionary_test
(
	date String,
	id String,
	value Int64
)
engine = MergeTree()
partition by date
order by id
settings index_granularity = 8192;
```

I also inserted one million key-value pairs into Redis.
The dictionary is like:
```
create dictionary redis_dict
(
	date String,
	id String,
	value Int64
)
PRIMARY KEY date, id
SOURCE(REDIS(
	host '127.0.0.1'
	port 6379
	storage_type 'hash_map'
	db_index 0
))
LAYOUT(COMPLEX_KEY_DIRECT())
```
When I execute this query: `SELECT COUNT(DISTINCT dictGet('redis_dict', 'value', tuple(date, id))) FROM redis_dictionary_test;`, ClickHouse seems stuck. Progress was in this state: 122.88 thousand rows, 5.84 MB (1.20 million rows/s., 56.83 MB/s.)  12% about five minutes. Finally, I canceled query.

I am sure Redis is fine. Because I monitored Redis and it could accept read and write commands.

I also executed this query on 1000, 10000 and 100000 rows of data. They can return data normally.

What happened to ClickHouse? Where can I find out the reason?
{
            throw Exception(ErrorCodes::NOT_IMPLEMENTED, "Method loadUpdatedAll is unsupported for RedisDictionarySource");
        }
        bool supportsSelectiveLoad() const override { return true; }
        Pipe loadIds(const std::vector<UInt64> & ids) override;
        Pipe loadKeys(const Columns & key_columns, const std::vector<size_t> & requested_rows) override;
        bool isModified() const override { return true; }
        bool hasUpdateField() const override { return false; }
        DictionarySourcePtr clone() const override { return std::make_shared<RedisDictionarySource>(*this); }
        std::string toString() const override;
    private:
        static RedisStorageType parseStorageType(const std::string& storage_type);
        const DictionaryStructure dict_struct;
        const std::string host;
        const UInt16 port;
        const UInt8 db_index;
        const std::string password;
        const RedisStorageType storage_type;
        Block sample_block;
        std::shared_ptr<Poco::Redis::Client> client;
    };
}