void FunctionCoalesce::executeImpl(Block & block, const ColumnNumbers & arguments, size_t result)
{
/// coalesce(arg0, arg1, ..., argN) is essentially
/// multiIf(isNotNull(arg0), assumeNotNull(arg0), isNotNull(arg1), assumeNotNull(arg1), ..., argN)
/// with constant NULL arguments removed.
ColumnNumbers filtered_args;
filtered_args.reserve(arguments.size());
for (const auto & arg : arguments)
{
const auto & type = block.getByPosition(arg).type;
if (type->onlyNull())
continue;
filtered_args.push_back(arg);
if (!type->isNullable())
break;
}
FunctionIsNotNull is_not_null;
FunctionAssumeNotNull assume_not_null;
ColumnNumbers multi_if_args;
Block temp_block = block;
for (size_t i = 0; i < filtered_args.size(); ++i)
{
size_t res_pos = temp_block.columns();
bool is_last = i + 1 == filtered_args.size();
if (is_last)
{
multi_if_args.push_back(filtered_args[i]);
}
else
{
temp_block.insert({nullptr, std::make_shared<DataTypeUInt8>(), ""});
is_not_null.execute(temp_block, {filtered_args[i]}, res_pos);
temp_block.insert({nullptr, removeNullable(block.getByPosition(filtered_args[i]).type), ""});
assume_not_null.execute(temp_block, {filtered_args[i]}, res_pos + 1);
multi_if_args.push_back(res_pos);
multi_if_args.push_back(res_pos + 1);
}
}
/// If all arguments appeared to be NULL.
if (multi_if_args.empty())
{
block.getByPosition(result).column = block.getByPosition(result).type->createColumnConstWithDefaultValue(block.rows());
return;
}
if (multi_if_args.size() == 1)
{
block.getByPosition(result).column = block.getByPosition(multi_if_args.front()).column;
return;
}
FunctionMultiIf{context}.execute(temp_block, multi_if_args, result);
ColumnPtr res = std::move(temp_block.getByPosition(result).column);
/// if last argument is not nullable, result should be also not nullable
if (!block.getByPosition(multi_if_args.back()).column->isColumnNullable() && res->isColumnNullable())
res = static_cast<const ColumnNullable &>(*res).getNestedColumnPtr();
block.getByPosition(result).column = std::move(res);
}
void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result, size_t input_rows_count) override
{
/// coalesce(arg0, arg1, ..., argN) is essentially
/// multiIf(isNotNull(arg0), assumeNotNull(arg0), isNotNull(arg1), assumeNotNull(arg1), ..., argN)
/// with constant NULL arguments removed.
ColumnNumbers filtered_args;
filtered_args.reserve(arguments.size());
for (const auto & arg : arguments)
{
const auto & type = block.getByPosition(arg).type;
if (type->onlyNull())
continue;
filtered_args.push_back(arg);
if (!type->isNullable())
break;
}
auto is_not_null = FunctionFactory::instance().get("isNotNull", context);
auto assume_not_null = FunctionFactory::instance().get("assumeNotNull", context);
auto multi_if = FunctionFactory::instance().get("multiIf", context);
ColumnNumbers multi_if_args;
Block temp_block = block;
for (size_t i = 0; i < filtered_args.size(); ++i)
{
size_t res_pos = temp_block.columns();
bool is_last = i + 1 == filtered_args.size();
if (is_last)
{
multi_if_args.push_back(filtered_args[i]);
}
else
{
temp_block.insert({nullptr, std::make_shared<DataTypeUInt8>(), ""});
is_not_null->build({temp_block.getByPosition(filtered_args[i])})->execute(temp_block, {filtered_args[i]}, res_pos, input_rows_count);
temp_block.insert({nullptr, removeNullable(block.getByPosition(filtered_args[i]).type), ""});
assume_not_null->build({temp_block.getByPosition(filtered_args[i])})->execute(temp_block, {filtered_args[i]}, res_pos + 1, input_rows_count);
multi_if_args.push_back(res_pos);
multi_if_args.push_back(res_pos + 1);
}
}
/// If all arguments appeared to be NULL.
if (multi_if_args.empty())
{
block.getByPosition(result).column = block.getByPosition(result).type->createColumnConstWithDefaultValue(input_rows_count);
return;
}
if (multi_if_args.size() == 1)
{
block.getByPosition(result).column = block.getByPosition(multi_if_args.front()).column;
return;
}
ColumnsWithTypeAndName multi_if_args_elems;
multi_if_args_elems.reserve(multi_if_args.size());
for (auto column_num : multi_if_args)
multi_if_args_elems.emplace_back(temp_block.getByPosition(column_num));
multi_if->build(multi_if_args_elems)->execute(temp_block, multi_if_args, result, input_rows_count);
ColumnPtr res = std::move(temp_block.getByPosition(result).column);
/// if last argument is not nullable, result should be also not nullable
if (!block.getByPosition(multi_if_args.back()).column->isColumnNullable() && res->isColumnNullable())
res = static_cast<const ColumnNullable &>(*res).getNestedColumnPtr();
block.getByPosition(result).column = std::move(res);
}