```
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 getCodecOrDefault(column_name, CompressionCodecFactory::instance().getDefaultCodec());
}
ASTPtr ColumnsDescription::getCodecDescOrDefault(const String & column_name, CompressionCodecPtr default_codec) const
{
    const auto it = columns.get<1>().find(column_name);
    if (it == columns.get<1>().end() || !it->codec)
        return default_codec->getFullCodecDesc();
    return it->codec;
}
ColumnsDescription::ColumnTTLs ColumnsDescription::getColumnTTLs() const
{
    ColumnTTLs ret;
    for (const auto & column : columns)
        if (column.ttl)
            ret.emplace(column.name, column.ttl);
    return ret;
}
String ColumnsDescription::toString() const
{
    WriteBufferFromOwnString buf;
    writeCString("columns format version: 1\n", buf);
    DB::writeText(columns.size(), buf);
    writeCString(" columns:\n", buf);
    for (const ColumnDescription & column : columns)
        column.writeText(buf);
    return buf.str();
}
ColumnsDescription ColumnsDescription::parse(const String & str)