ClickHouse/dbms/src/Functions/arrayWithConstant.cpp
2019-04-10 22:57:30 +03:00

85 lines
2.8 KiB
C++

#include <Functions/IFunction.h>
#include <Functions/FunctionHelpers.h>
#include <Functions/FunctionFactory.h>
#include <DataTypes/DataTypeArray.h>
#include <DataTypes/DataTypesNumber.h>
#include <Columns/ColumnArray.h>
namespace DB
{
namespace ErrorCodes
{
extern const int ILLEGAL_TYPE_OF_ARGUMENT;
extern const int TOO_LARGE_ARRAY_SIZE;
}
/// Reasonable threshold.
static constexpr size_t max_arrays_size_in_block = 1000000000;
/* arrayWithConstant(num, const) - make array of constants with length num.
* arrayWithConstant(3, 'hello') = ['hello', 'hello', 'hello']
* arrayWithConstant(1, 'hello') = ['hello']
* arrayWithConstant(0, 'hello') = []
*/
class FunctionArrayWithConstant : public IFunction
{
public:
static constexpr auto name = "arrayWithConstant";
static FunctionPtr create(const Context &) { return std::make_shared<FunctionArrayWithConstant>(); }
String getName() const override { return name; }
size_t getNumberOfArguments() const override { return 2; }
DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
{
if (!isNumber(arguments[0]))
throw Exception("Illegal type " + arguments[0]->getName() +
" of argument of function " + getName() +
", expected Integer", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
return std::make_shared<DataTypeArray>(arguments[1]);
}
bool useDefaultImplementationForConstants() const override { return true; }
bool useDefaultImplementationForNulls() const override { return false; }
void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result, size_t num_rows) override
{
const auto * col_num = block.getByPosition(arguments[0]).column.get();
const auto * col_value = block.getByPosition(arguments[1]).column.get();
auto offsets_col = ColumnArray::ColumnOffsets::create();
ColumnArray::Offsets & offsets = offsets_col->getData();
offsets.reserve(num_rows);
ColumnArray::Offset offset = 0;
for (size_t i = 0; i < num_rows; ++i)
{
auto array_size = col_num->getInt(i);
if (unlikely(array_size < 0))
throw Exception("Array size cannot be negative: while executing function " + getName(), ErrorCodes::TOO_LARGE_ARRAY_SIZE);
offset += array_size;
if (unlikely(offset > max_arrays_size_in_block))
throw Exception("Too large array size while executing function " + getName(), ErrorCodes::TOO_LARGE_ARRAY_SIZE);
offsets.push_back(offset);
}
block.getByPosition(result).column = ColumnArray::create(col_value->replicate(offsets), std::move(offsets_col));
}
};
void registerFunctionArrayWithConstant(FunctionFactory & factory)
{
factory.registerFunction<FunctionArrayWithConstant>();
}
}