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?
{
        if (!client->isConnected())
            client->connect(host, port);
        if (key_columns.size() != dict_struct.key->size())
            throw Exception(ErrorCodes::LOGICAL_ERROR, "The size of key_columns does not equal to the size of dictionary key");
        RedisArray keys;
        for (auto row : requested_rows)
        {
            RedisArray key;
            for (size_t i = 0; i < key_columns.size(); ++i)
            {
                const auto & type = dict_struct.key->at(i).type;
                if (isInteger(type))
                    key << DB::toString(key_columns[i]->get64(row));
                else if (isString(type))
                    key << get<String>((*key_columns[i])[row]);
                else
                    throw Exception(ErrorCodes::LOGICAL_ERROR, "Unexpected type of key in Redis dictionary");
            }
            keys.add(key);
        }
        return Pipe(std::make_shared<RedisSource>(client, std::move(keys), storage_type, sample_block, max_block_size));
    }
    String RedisDictionarySource::toString() const