**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

#pragma once
#include <DataStreams/IBlockInputStream.h>
#include <Core/Row.h>
#include <Core/Block.h>
#include <common/types.h>
#include <Core/NamesAndTypes.h>
#include <Storages/IStorage.h>
#include <Storages/MergeTree/MergeTreeIndexGranularity.h>
#include <Storages/MergeTree/MergeTreeIndexGranularityInfo.h>
#include <Storages/MergeTree/MergeTreeIndices.h>
#include <Storages/MergeTree/MergeTreePartInfo.h>
#include <Storages/MergeTree/MergeTreePartition.h>
#include <Storages/MergeTree/MergeTreeDataPartChecksum.h>
#include <Storages/MergeTree/MergeTreeDataPartTTLInfo.h>
#include <Storages/MergeTree/MergeTreeIOSettings.h>
#include <Storages/MergeTree/KeyCondition.h>
#include <Columns/IColumn.h>
#include <Poco/Path.h>
#include <shared_mutex>
namespace zkutil
{
    class ZooKeeper;