**Use case**

Currently, `system.replicas` table has `total_replicas` and `active_replicas` columns which are useful to check/alert when some replicas are down. One problem, these columns are numbers. They tell when there is a problem, but you need to further check ZooKeeper or query all the nodes to detect what exact replicas (hosts) are down/inactive/have problems.

**Describe the solution you'd like**

Add a replicas column maybe as a map which would contain the replica name, and it's status. Or, add 2 array columns with `replica_names` and `active_replica_names`

**Alternative**

Something along the line

```sql
select path, value from system.zookeeper where path IN (
    select concat(path, '/', name) from system.zookeeper where path in (select concat(zookeeper_path, '/replicas') from system.replicas)
)
and name = 'is_active'
```
{
    String part_path = fs::path(replica_path) / "parts" / part_name;
    if (has_children)
    {
        ops.emplace_back(zkutil::makeRemoveRequest(fs::path(part_path) / "checksums", -1));
        ops.emplace_back(zkutil::makeRemoveRequest(fs::path(part_path) / "columns", -1));
    }
    ops.emplace_back(zkutil::makeRemoveRequest(part_path, -1));
}
void StorageReplicatedMergeTree::removePartFromZooKeeper(const String & part_name)
{
    auto zookeeper = getZooKeeper();
    String part_path = fs::path(replica_path) / "parts" / part_name;
    Coordination::Stat stat;
    
    if (!zookeeper->exists(part_path, &stat))
        return;
    Coordination::Requests ops;
    removePartFromZooKeeper(part_name, ops, stat.numChildren > 0);
    zookeeper->multi(ops);
}
void StorageReplicatedMergeTree::removePartAndEnqueueFetch(const String & part_name)