ClickHouse/dbms/include/DB/DataStreams/AddingDefaultBlockInputStream.h

#pragma once

#include <Poco/SharedPtr.h>

#include <DB/DataStreams/IProfilingBlockInputStream.h>
#include <DB/Interpreters/evaluateMissingDefaults.h>
#include <DB/Columns/ColumnConst.h>

#include <DB/Storages/ColumnDefault.h>


namespace DB
{


/** Добавляет в блок недостающие столбцы со значениями по-умолчанию.
  * Эти столбцы - материалированные (не константы).
  */
class AddingDefaultBlockInputStream : public IProfilingBlockInputStream
{
public:
	AddingDefaultBlockInputStream(
		BlockInputStreamPtr input_,
		NamesAndTypesListPtr required_columns_,
		const ColumnDefaults & column_defaults_,
		const Context & context_)
		: required_columns(required_columns_),
		  column_defaults(column_defaults_), context(context_)
	{
		children.push_back(input_);
	}

	AddingDefaultBlockInputStream(BlockInputStreamPtr input_, NamesAndTypesListPtr required_columns_, const Context & context_)
		: AddingDefaultBlockInputStream{input_, required_columns_, ColumnDefaults{}, context_}
	{
	}

	String getName() const override { return "AddingDefault"; }

	String getID() const override
	{
		std::stringstream res;
		res << "AddingDefault(" << children.back()->getID();

		for (NamesAndTypesList::const_iterator it = required_columns->begin(); it != required_columns->end(); ++it)
			res << ", " << it->name << ", " << it->type->getName();

		res << ")";
		return res.str();
	}

protected:
	Block readImpl() override
	{
		Block res = children.back()->read();
		if (!res)
			return res;
		/** @todo if somehow block does not contain values for implicitly-defaulted columns that are prerequisites
		 *	for explicitly-defaulted ones, exception will be thrown during evaluating such columns
		 *	(implicitly-defaulted columns are evaluated on the line after following one. */
		evaluateMissingDefaults(res, *required_columns, column_defaults, context);
		res.addDefaults(*required_columns);
		return res;
	}

private:
	NamesAndTypesListPtr required_columns;
	const ColumnDefaults & column_defaults;
	Context context;
};

}