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

#pragma once

#include <iomanip>

#include <Yandex/logger_useful.h>

#include <DB/Columns/ColumnAggregateFunction.h>

#include <DB/DataStreams/IProfilingBlockInputStream.h>


namespace DB
{

using Poco::SharedPtr;


/** Преобразует агрегатные функции (с промежуточным состоянием) в потоке блоков в конечные значения.
  */
class FinalizingAggregatedBlockInputStream : public IProfilingBlockInputStream
{
public:
	FinalizingAggregatedBlockInputStream(BlockInputStreamPtr input_)
		: log(&Logger::get("FinalizingAggregatedBlockInputStream"))
	{
		children.push_back(input_);
	}

	String getName() const { return "FinalizingAggregatedBlockInputStream"; }

	String getID() const
	{
		std::stringstream res;
		res << "FinalizingAggregated(" << children.back()->getID() << ")";
		return res.str();
	}

protected:
	Block readImpl()
	{
		Block res = children.back()->read();

		if (!res)
			return res;

		LOG_TRACE(log, "Finalizing aggregate functions");
		Stopwatch watch;

		size_t rows = res.rows();
		size_t columns = res.columns();
		for (size_t i = 0; i < columns; ++i)
		{
			ColumnWithNameAndType & column = res.getByPosition(i);
			if (ColumnAggregateFunction * col = dynamic_cast<ColumnAggregateFunction *>(&*column.column))
			{
				ColumnAggregateFunction::Container_t & data = col->getData();
				IAggregateFunction * func = col->getFunction();
				column.type = func->getReturnType();
				ColumnPtr finalized_column = column.type->createColumn();
				finalized_column->reserve(rows);

				for (size_t j = 0; j < rows; ++j)
					finalized_column->insert(func->getResult(data[j]));

				column.column = finalized_column;
			}
		}

		double elapsed_seconds = watch.elapsedSeconds();
		if (elapsed_seconds > 0.001)
		{
			LOG_TRACE(log, std::fixed << std::setprecision(3)
				<< "Finalized aggregate functions. "
				<< res.rows() << " rows, " << res.bytes() / 1048576.0 << " MiB"
				<< " in " << elapsed_seconds << " sec."
				<< " (" << res.rows() / elapsed_seconds << " rows/sec., " << res.bytes() / elapsed_seconds / 1048576.0 << " MiB/sec.)");
		}

		return res;
	}

private:
	Logger * log;
};

}