**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'
```
sorting_key.recalculateWithNewAST(order_by_ast, new_metadata.columns, getContext());
            if (primary_key.definition_ast == nullptr)
            {
                
                
                auto old_sorting_key_ast = old_metadata.getSortingKey().definition_ast;
                primary_key = KeyDescription::getKeyFromAST(
                    old_sorting_key_ast, new_metadata.columns, getContext());
            }
        }
        if (metadata_diff.sampling_expression_changed)
        {
            auto sample_by_ast = parse_key_expr(metadata_diff.new_sampling_expression);
            new_metadata.sampling_key.recalculateWithNewAST(sample_by_ast, new_metadata.columns, getContext());
        }
        if (metadata_diff.skip_indices_changed)
            new_metadata.secondary_indices = IndicesDescription::parse(metadata_diff.new_skip_indices, new_columns, getContext());
        if (metadata_diff.constraints_changed)
            new_metadata.constraints = ConstraintsDescription::parse(metadata_diff.new_constraints);
        if (metadata_diff.projections_changed)
            new_metadata.projections = ProjectionsDescription::parse(metadata_diff.new_projections, new_columns, getContext());
        if (metadata_diff.ttl_table_changed)
        {
            if (!metadata_diff.new_ttl_table.empty())
            {
                ParserTTLExpressionList parser;
                auto ttl_for_table_ast = parseQuery(parser, metadata_diff.new_ttl_table, 0, DBMS_DEFAULT_MAX_PARSER_DEPTH);
                new_metadata.table_ttl = TTLTableDescription::getTTLForTableFromAST(
                    ttl_for_table_ast, new_metadata.columns, getContext(), new_metadata.primary_key);
            }