**Describe the bug**

I have a table like:

```
CREATE TABLE test (
    time DateTime64(3)
    ...
) ENGINE = MergeTree()
PARTITION BY toStartOfInterval(time, INTERVAL 1 HOUR)
...
```

But when I search in `system.parts` it does not appear to have the `min/max` columns appropriately set?

```
partition:                             2020-06-01 01:00:00
min_date:                              1970-01-01
max_date:                              1970-01-01
min_time:                              1970-01-01 00:00:00
max_time:                              1970-01-01 00:00:00
```

I assume that if these were correctly set, doing a `select toStartOfInterval(time, interval 1 day), count()` type query would be pretty instant rather than trying to scan everything? I am guessing this is due to the `DateTime64` type in use?

Clickhouse 20.11.3.3

const KeyDescription & key,
    const IndicesDescription & indices,
    const ColumnsDescription & columns,
    const Context & context)
{
    ASTPtr combined_expr_list = key.expression_list_ast->clone();
    for (const auto & index : indices)
        for (const auto & index_expr : index.expression_list_ast->children)
            combined_expr_list->children.push_back(index_expr->clone());
    auto syntax_result = TreeRewriter(context).analyze(combined_expr_list, columns.getAllPhysical());
    return ExpressionAnalyzer(combined_expr_list, syntax_result, context).getActions(false);
}
}
ExpressionActionsPtr MergeTreeData::getMinMaxExpr(const KeyDescription & partition_key, const ExpressionActionsSettings & settings)
{
    NamesAndTypesList partition_key_columns;
    if (!partition_key.column_names.empty())
        partition_key_columns = partition_key.expression->getRequiredColumnsWithTypes();
    return std::make_shared<ExpressionActions>(std::make_shared<ActionsDAG>(partition_key_columns), settings);
}
Names MergeTreeData::getMinMaxColumnsNames(const KeyDescription & partition_key)
{
    if (!partition_key.column_names.empty())
        return partition_key.expression->getRequiredColumns();
    return {};
}
DataTypes MergeTreeData::getMinMaxColumnsTypes(const KeyDescription & partition_key)