```
CREATE TABLE a
(
    `number` UInt64,
    `x` MATERIALIZED x
)
ENGINE = MergeTree
ORDER BY number;
-- that should fail!

insert into a values (1);
Received exception from server (version 21.7.1):
Code: 47. DB::Exception: Received from localhost:9000. DB::Exception: Missing columns: 'x' while processing query: 'CAST(x, 'UInt8') AS x', required columns: 'x' 'x'. 
```
{
    return getWithSubcolumns(getAll());
}
NamesAndTypesList ColumnsDescription::getAllPhysicalWithSubcolumns() const
{
    return getWithSubcolumns(getAllPhysical());
}
bool ColumnsDescription::hasDefaults() const
{
    for (const auto & column : columns)
        if (column.default_desc.expression)
            return true;
    return false;
}
ColumnDefaults ColumnsDescription::getDefaults() const
{
    ColumnDefaults ret;
    for (const auto & column : columns)
        if (column.default_desc.expression)
            ret.emplace(column.name, column.default_desc);
    return ret;
}
bool ColumnsDescription::hasDefault(const String & column_name) const