NamesAndTypesList getStructureOfRemoteTable(
const Cluster & cluster,
const std::string & database,
const std::string & table,
const Context & context)
{
/// Запрос на описание таблицы
String query = "DESC TABLE " + backQuoteIfNeed(database) + "." + backQuoteIfNeed(table);
Settings settings = context.getSettings();
NamesAndTypesList res;
/// Отправляем на первый попавшийся удалённый шард.
const auto & shard_info = cluster.getAnyShardInfo();
if (shard_info.isLocal())
return context.getTable(database, table)->getColumnsList();
ConnectionPoolPtr pool = shard_info.pool;
BlockInputStreamPtr input =
std::make_shared<RemoteBlockInputStream>(
pool.get(), query, &settings, nullptr,
Tables(), QueryProcessingStage::Complete, context);
input->readPrefix();
const DataTypeFactory & data_type_factory = DataTypeFactory::instance();
while (Block current = input->read())
{
ColumnPtr name = current.getByName("name").column;
ColumnPtr type = current.getByName("type").column;
size_t size = name->size();
for (size_t i = 0; i < size; ++i)
{
String column_name = (*name)[i].get<const String &>();
String data_type_name = (*type)[i].get<const String &>();
res.emplace_back(column_name, data_type_factory.get(data_type_name));
}
}
return res;
}
ColumnPtr recursiveLowCardinalityConversion(const ColumnPtr & column, const DataTypePtr & from_type, const DataTypePtr & to_type)
{
if (!column)
return column;
if (from_type->equals(*to_type))
return column;
if (const auto * column_const = typeid_cast<const ColumnConst *>(column.get()))
return ColumnConst::create(recursiveLowCardinalityConversion(column_const->getDataColumnPtr(), from_type, to_type),
column_const->size());
if (const auto * low_cardinality_type = typeid_cast<const DataTypeLowCardinality *>(from_type.get()))
{
if (to_type->equals(*low_cardinality_type->getDictionaryType()))
return column->convertToFullColumnIfLowCardinality();
}
if (const auto * low_cardinality_type = typeid_cast<const DataTypeLowCardinality *>(to_type.get()))
{
if (from_type->equals(*low_cardinality_type->getDictionaryType()))
{
auto col = low_cardinality_type->createColumn();
static_cast<ColumnLowCardinality &>(*col).insertRangeFromFullColumn(*column, 0, column->size());
return std::move(col);
}
}
if (const auto * from_array_type = typeid_cast<const DataTypeArray *>(from_type.get()))
{
if (const auto * to_array_type = typeid_cast<const DataTypeArray *>(to_type.get()))
{
const auto * column_array = typeid_cast<const ColumnArray *>(column.get());
if (!column_array)
throw Exception("Unexpected column " + column->getName() + " for type " + from_type->getName(),
ErrorCodes::ILLEGAL_COLUMN);
auto & nested_from = from_array_type->getNestedType();
auto & nested_to = to_array_type->getNestedType();
return ColumnArray::create(
recursiveLowCardinalityConversion(column_array->getDataPtr(), nested_from, nested_to),
column_array->getOffsetsPtr());
}
}
if (const auto * from_tuple_type = typeid_cast<const DataTypeTuple *>(from_type.get()))
{
if (const auto * to_tuple_type = typeid_cast<const DataTypeTuple *>(to_type.get()))
{
const auto * column_tuple = typeid_cast<const ColumnTuple *>(column.get());
if (!column_tuple)
throw Exception("Unexpected column " + column->getName() + " for type " + from_type->getName(),
ErrorCodes::ILLEGAL_COLUMN);
Columns columns = column_tuple->getColumns();
auto & from_elements = from_tuple_type->getElements();
auto & to_elements = to_tuple_type->getElements();
for (size_t i = 0; i < columns.size(); ++i)
{
auto & element = columns[i];
element = recursiveLowCardinalityConversion(element, from_elements.at(i), to_elements.at(i));
}
return ColumnTuple::create(columns);
}
}
throw Exception("Cannot convert: " + from_type->getName() + " to " + to_type->getName(), ErrorCodes::TYPE_MISMATCH);
}