text: #include <Functions/IFunctionImpl.h>
  #include <Functions/FunctionFactory.h>
  #include <Functions/GatherUtils/GatherUtils.h>
  #include <DataTypes/DataTypeArray.h>
  #include <DataTypes/DataTypeNullable.h>
  #include <DataTypes/getLeastSupertype.h>
  #include <Columns/ColumnArray.h>
  #include <Columns/ColumnConst.h>
  #include <Interpreters/castColumn.h>
  #include <IO/WriteHelpers.h>
  #include <Common/typeid_cast.h>
  
  
  namespace DB
  {
  
  namespace ErrorCodes
  {
      extern const int LOGICAL_ERROR;
      extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
      extern const int ILLEGAL_TYPE_OF_ARGUMENT;
  }
  
  class FunctionArrayResize : public IFunction
  {
  public:
      static constexpr auto name = "arrayResize";
      static FunctionPtr create(const Context &) { return std::make_shared<FunctionArrayResize>(); }
  
      String getName() const override { return name; }
  
      bool isVariadic() const override { return true; }
      size_t getNumberOfArguments() const override { return 0; }
  
      DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
      {
          const size_t number_of_arguments = arguments.size();
  
          if (number_of_arguments < 2 || number_of_arguments > 3)
              throw Exception("Number of arguments for function " + getName() + " doesn't match: passed "
                              + toString(number_of_arguments) + ", should be 2 or 3",
                              ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
  
          if (arguments[0]->onlyNull())
              return arguments[0];
  
          auto array_type = typeid_cast<const DataTypeArray *>(arguments[0].get());
          if (!array_type)
              throw Exception("First argument for function " + getName() + " must be an array but it has type "
                              + arguments[0]->getName() + ".", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
  
          if (WhichDataType(array_type->getNestedType()).isNothing())
              throw Exception("Function " + getName() + " cannot resize " + array_type->getName(), ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
  
          if (!isInteger(removeNullable(arguments[1])) && !arguments[1]->onlyNull())
              throw Exception(
                      "Argument " + toString(1) + " for function " + getName() + " must be integer but it has type "
                      + arguments[1]->getName() + ".", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
  
          if (number_of_arguments == 2)
              return arguments[0];
          else /* if (number_of_arguments == 3) */
              return std::make_shared<DataTypeArray>(getLeastSupertype({array_type->getNestedType(), arguments[2]}));
      }
  
      void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result, size_t input_rows_count) override
      {
          const auto & return_type = block.getByPosition(result).type;
  
          if (return_type->onlyNull())
          {
              block.getByPosition(result).column = return_type->createColumnConstWithDefaultValue(input_rows_count);
              return;
          }
  
          auto result_column = return_type->createColumn();
  
          auto array_column = block.getByPosition(arguments[0]).column;
          auto size_column = block.getByPosition(arguments[1]).column;
  
          if (!block.getByPosition(arguments[0]).type->equals(*return_type))
              array_column = castColumn(block.getByPosition(arguments[0]), return_type);
  
          const DataTypePtr & return_nested_type = typeid_cast<const DataTypeArray &>(*return_type).getNestedType();
          size_t size = array_column->size();
  
          ColumnPtr appended_column;
          if (arguments.size() == 3)
          {
              appended_column = block.getByPosition(arguments[2]).column;
              if (!block.getByPosition(arguments[2]).type->equals(*return_nested_type))
                  appended_column = castColumn(block.getByPosition(arguments[2]), return_nested_type);
          }
          else
              appended_column = return_nested_type->createColumnConstWithDefaultValue(size);
  
          std::unique_ptr<GatherUtils::IArraySource> array_source;
          std::unique_ptr<GatherUtils::IValueSource> value_source;
  
          bool is_const = false;
  
          if (auto const_array_column = typeid_cast<const ColumnConst *>(array_column.get()))
          {
              is_const = true;
              array_column = const_array_column->getDataColumnPtr();
          }
  
          if (auto argument_column_array = typeid_cast<const ColumnArray *>(array_column.get()))
              array_source = GatherUtils::createArraySource(*argument_column_array, is_const, size);
          else
              throw Exception{"First arguments for function " + getName() + " must be array.", ErrorCodes::LOGICAL_ERROR};
  
  
          bool is_appended_const = false;
          if (auto const_appended_column = typeid_cast<const ColumnConst *>(appended_column.get()))
          {
              is_appended_const = true;
              appended_column = const_appended_column->getDataColumnPtr();
          }
  
          value_source = GatherUtils::createValueSource(*appended_column, is_appended_const, size);
  
          auto sink = GatherUtils::createArraySink(typeid_cast<ColumnArray &>(*result_column), size);
  
          if (isColumnConst(*size_column))
              GatherUtils::resizeConstantSize(*array_source, *value_source, *sink, size_column->getInt(0));
          else
              GatherUtils::resizeDynamicSize(*array_source, *value_source, *sink, *size_column);
  
          block.getByPosition(result).column = std::move(result_column);
      }
  
      bool useDefaultImplementationForConstants() const override { return true; }
      bool useDefaultImplementationForNulls() const override { return false; }
  };
  
  
  void registerFunctionArrayResize(FunctionFactory & factory)
  {
      factory.registerFunction<FunctionArrayResize>();
  }
  
  }
  