Function recursiveConvertColumn

src/DataTypes/recursiveTypeConversions.h:58–115

template <typename FromColumn>
ColumnPtr recursiveConvertColumn(const ColumnPtr & column, Fn<ColumnPtr(const FromColumn &)> auto && func)
{
    if (!column)
        return column;

    if (const auto * from_column = typeid_cast<const FromColumn *>(column.get()))
        return func(*from_column);

    if (const auto * column_array = typeid_cast<const ColumnArray *>(column.get()))
    {
        const auto & data = column_array->getDataPtr();
        auto converted = recursiveConvertColumn<FromColumn>(data, func);
        if (data.get() == converted.get())
            return column;

        return ColumnArray::create(converted, column_array->getOffsetsPtr());
    }

    if (const auto * column_const = typeid_cast<const ColumnConst *>(column.get()))
    {
        const auto & nested = column_const->getDataColumnPtr();
        auto converted = recursiveConvertColumn<FromColumn>(nested, func);
        if (nested.get() == converted.get())
            return column;

        return ColumnConst::create(converted, column_const->size());
    }

    if (const auto * column_map = typeid_cast<const ColumnMap *>(column.get()))
    {
        const auto & nested = column_map->getNestedColumnPtr();
        auto converted = recursiveConvertColumn<FromColumn>(nested, func);
        if (nested.get() == converted.get())
            return column;

        return ColumnMap::create(converted);
    }

    if (const auto * column_nullable = typeid_cast<const ColumnNullable *>(column.get()))
    {
        const auto & nested = column_nullable->getNestedColumnPtr();
        auto converted = recursiveConvertColumn<FromColumn>(nested, func);
        if (nested.get() == converted.get())
            return column;

        return ColumnNullable::create(converted, column_nullable->getNullMapColumnPtr());
    }

    if (const auto * column_tuple = typeid_cast<const ColumnTuple *>(column.get()))
    {
        auto columns = column_tuple->getColumns();
        for (auto & element : columns)
            element = recursiveConvertColumn<FromColumn>(element, func);
        return ColumnTuple::create(columns);
    }

    return column;
}