Function flattenTupleColumnsRecursive

src/DataTypes/NestedUtils.cpp:383–410

Flatten tuple columns: input a vector of columns, return a new vector with all tuples expanded All tuples are flattened recursively

/// Flatten tuple columns: input a vector of columns, return a new vector with all tuples expanded
/// All tuples are flattened recursively
Columns flattenTupleColumnsRecursive(const Block & header, const Columns & columns)
{
    if (header.columns() != columns.size())
    {
        throw Exception(
            ErrorCodes::LOGICAL_ERROR,
            "Header columns count ({}) does not match columns count ({}) in flattenTupleColumns",
            header.columns(),
            columns.size());
    }

    Columns result;
    result.reserve(columns.size()); /// Lower bound: every column flattens to at least one leaf.

    for (size_t i = 0; i < columns.size(); ++i)
    {
        const auto & header_col = header.getByPosition(i);
        flattenTupleRecursiveImpl(
            columns[i], header_col.type,
            [&result](const ColumnPtr & col, const DataTypePtr &, const String &, const Strings &)
            {
                result.push_back(col);
            },
            {}, {});
    }

    return result;
}

static ColumnPtr reconstructTupleColumnImpl(const DataTypePtr & data_type, const Columns & flattened_columns, size_t & flattened_idx)
{