```
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'. 
```
{
    NamesAndTypesList ret;
    for (const auto & col : columns)
        if (col.default_desc.kind == ColumnDefaultKind::Materialized)
            ret.emplace_back(col.name, col.type);
    return ret;
}
NamesAndTypesList ColumnsDescription::getAliases() const
{
    NamesAndTypesList ret;
    for (const auto & col : columns)
        if (col.default_desc.kind == ColumnDefaultKind::Alias)
            ret.emplace_back(col.name, col.type);
    return ret;
}
NamesAndTypesList ColumnsDescription::getAll() const
{
    NamesAndTypesList ret;
    for (const auto & col : columns)
        ret.emplace_back(col.name, col.type);
    return ret;
}
bool ColumnsDescription::has(const String & column_name) const
{
    return columns.get<1>().find(column_name) != columns.get<1>().end();
}
bool ColumnsDescription::hasNested(const String & column_name) const