```
CREATE TABLE t (x UInt8, PROJECTION p (SELECT x GROUP BY x)) ENGINE = MergeTree ORDER BY ();
INSERT INTO t VALUES (0);

SET group_by_overflow_mode = 'any', max_rows_to_group_by = 1000, totals_mode = 'after_having_auto';
SELECT x FROM t GROUP BY x WITH TOTALS;
```
{
    MergeTreeData * src_data = dynamic_cast<MergeTreeData *>(&source_table);
    if (!src_data)
        throw Exception("Table " + source_table.getStorageID().getNameForLogs() +
                        " supports attachPartitionFrom only for MergeTree family of table engines."
                        " Got " + source_table.getName(), ErrorCodes::NOT_IMPLEMENTED);
    if (my_snapshot->getColumns().getAllPhysical().sizeOfDifference(src_snapshot->getColumns().getAllPhysical()))
        throw Exception("Tables have different structure", ErrorCodes::INCOMPATIBLE_COLUMNS);
    auto query_to_string = [] (const ASTPtr & ast)
    {
        return ast ? queryToString(ast) : "";
    };
    if (query_to_string(my_snapshot->getSortingKeyAST()) != query_to_string(src_snapshot->getSortingKeyAST()))
        throw Exception("Tables have different ordering", ErrorCodes::BAD_ARGUMENTS);
    if (query_to_string(my_snapshot->getPartitionKeyAST()) != query_to_string(src_snapshot->getPartitionKeyAST()))
        throw Exception("Tables have different partition key", ErrorCodes::BAD_ARGUMENTS);
    if (format_version != src_data->format_version)
        throw Exception("Tables have different format_version", ErrorCodes::BAD_ARGUMENTS);
    if (query_to_string(my_snapshot->getPrimaryKeyAST()) != query_to_string(src_snapshot->getPrimaryKeyAST()))
        throw Exception("Tables have different primary key", ErrorCodes::BAD_ARGUMENTS);
    return *src_data;
}
MergeTreeData & MergeTreeData::checkStructureAndGetMergeTreeData(