ClickHouse/dbms/src/Columns/ColumnConst.cpp

#include <DB/DataTypes/DataTypeString.h>
#include <DB/DataTypes/DataTypeFixedString.h>
#include <DB/DataTypes/DataTypeArray.h>

#include <DB/Columns/ColumnString.h>
#include <DB/Columns/ColumnConst.h>
#include <DB/Columns/ColumnArray.h>
#include <DB/Columns/ColumnTuple.h>
#include <DB/Columns/ColumnFixedString.h>
#include <DB/Columns/ColumnNullable.h>
#include <DB/DataTypes/DataTypeTuple.h>
#include <ext/enumerate.hpp>


namespace DB
{

template <>
ColumnPtr ColumnConst<Null>::convertToFullColumn() const
{
	/// We basically create a column whose rows have NULL values.
	ColumnPtr full_col = std::make_shared<ColumnUInt8>(size(), 0);
	ColumnPtr null_map = std::make_shared<ColumnUInt8>(size(), 1);
	return std::make_shared<ColumnNullable>(full_col, null_map);
}

template <> ColumnPtr ColumnConst<String>::convertToFullColumn() const
{
	if (!data_type || typeid_cast<const DataTypeString *>(&*data_type))
	{
		auto res = std::make_shared<ColumnString>();
		ColumnString::Offsets_t & offsets = res->getOffsets();
		ColumnString::Chars_t & vec = res->getChars();

		size_t string_size = data.size() + 1;
		size_t offset = 0;
		offsets.resize(s);
		vec.resize(s * string_size);

		for (size_t i = 0; i < s; ++i)
		{
			memcpy(&vec[offset], data.data(), string_size);
			offset += string_size;
			offsets[i] = offset;
		}

		return res;
	}
	else if (const DataTypeFixedString * type = typeid_cast<const DataTypeFixedString *>(&*data_type))
	{
		size_t n = type->getN();

		if (data.size() > n)
			throw Exception("Too long value for " + type->getName(), ErrorCodes::TOO_LARGE_STRING_SIZE);

		auto res = std::make_shared<ColumnFixedString>(n);
		ColumnFixedString::Chars_t & vec = res->getChars();

		vec.resize_fill(n * s);
		size_t offset = 0;

		for (size_t i = 0; i < s; ++i)
		{
			memcpy(&vec[offset], data.data(), data.size());
			offset += n;
		}

		return res;
	}
	else
		throw Exception("Invalid data type in ColumnConstString: " + data_type->getName(), ErrorCodes::LOGICAL_ERROR);
}


ColumnPtr ColumnConst<Array>::convertToFullColumn() const
{
	if (!data_type)
		throw Exception("No data type specified for ColumnConstArray", ErrorCodes::LOGICAL_ERROR);

	const DataTypeArray * type = typeid_cast<const DataTypeArray *>(&*data_type);
	if (!type)
		throw Exception("Non-array data type specified for ColumnConstArray", ErrorCodes::LOGICAL_ERROR);

	const Array & array = getDataFromHolderImpl();
	size_t array_size = array.size();

	const auto & nested_type = type->getNestedType();
	ColumnPtr nested_column;

	if (nested_type->isNull())
	{
		/// Special case: an array of Null is actually an array of Nullable(UInt8).
		nested_column = std::make_shared<ColumnNullable>(
			std::make_shared<ColumnUInt8>(), std::make_shared<ColumnUInt8>());
	}
	else
		nested_column = type->getNestedType()->createColumn();

	auto res = std::make_shared<ColumnArray>(nested_column);
	ColumnArray::Offsets_t & offsets = res->getOffsets();

	offsets.resize(s);
	for (size_t i = 0; i < s; ++i)
	{
		offsets[i] = (i + 1) * array_size;
		for (size_t j = 0; j < array_size; ++j)
			nested_column->insert(array[j]);
	}

	return res;
}


StringRef ColumnConst<Array>::getDataAt(size_t n) const
{
	throw Exception("Method getDataAt is not supported for " + this->getName(), ErrorCodes::NOT_IMPLEMENTED);
}

UInt64 ColumnConst<Array>::get64(size_t n) const
{
	throw Exception("Method get64 is not supported for " + this->getName(), ErrorCodes::NOT_IMPLEMENTED);
}

StringRef ColumnConst<Array>::getDataAtWithTerminatingZero(size_t n) const
{
	throw Exception("Method getDataAt is not supported for " + this->getName(), ErrorCodes::NOT_IMPLEMENTED);
}


ColumnPtr ColumnConst<Tuple>::convertToFullColumn() const
{
	return convertToTupleOfConstants()->convertToFullColumnIfConst();
}

ColumnPtr ColumnConst<Tuple>::convertToTupleOfConstants() const
{
	if (!data_type)
		throw Exception("No data type specified for ColumnConstTuple", ErrorCodes::LOGICAL_ERROR);

	const DataTypeTuple * type = typeid_cast<const DataTypeTuple *>(&*data_type);
	if (!type)
		throw Exception("Non-Tuple data type specified for ColumnConstTuple", ErrorCodes::LOGICAL_ERROR);

	/// Create columns for each element and convert to full columns.
	const DataTypes & element_types = type->getElements();
	size_t tuple_size = element_types.size();
	Block block;

	for (size_t i = 0; i < tuple_size; ++i)
		block.insert(ColumnWithTypeAndName{
			element_types[i]->createConstColumn(s, static_cast<const TupleBackend &>(*data)[i]),
			element_types[i],
			""});

	return std::make_shared<ColumnTuple>(block);
}

void ColumnConst<Tuple>::getExtremes(Field & min, Field & max) const
{
	min = *data;
	max = *data;
}

StringRef ColumnConst<Tuple>::getDataAt(size_t n) const
{
	throw Exception("Method getDataAt is not supported for " + this->getName(), ErrorCodes::NOT_IMPLEMENTED);
}

UInt64 ColumnConst<Tuple>::get64(size_t n) const
{
	throw Exception("Method get64 is not supported for " + this->getName(), ErrorCodes::NOT_IMPLEMENTED);
}

StringRef ColumnConst<Tuple>::getDataAtWithTerminatingZero(size_t n) const
{
	throw Exception("Method getDataAt is not supported for " + this->getName(), ErrorCodes::NOT_IMPLEMENTED);
}


}