ClickHouse/dbms/src/Storages/System/StorageSystemMetrics.cpp

#include <DB/Common/CurrentMetrics.h>
#include <DB/Columns/ColumnString.h>
#include <DB/DataTypes/DataTypeString.h>
#include <DB/DataTypes/DataTypesNumberFixed.h>
#include <DB/DataStreams/OneBlockInputStream.h>
#include <DB/Storages/System/StorageSystemMetrics.h>


namespace DB
{


StorageSystemMetrics::StorageSystemMetrics(const std::string & name_)
	: name(name_),
	columns
	{
		{"metric", 		new DataTypeString},
		{"value",		new DataTypeInt64},
	}
{
}

StoragePtr StorageSystemMetrics::create(const std::string & name_)
{
	return (new StorageSystemMetrics(name_))->thisPtr();
}


BlockInputStreams StorageSystemMetrics::read(
	const Names & column_names,
	ASTPtr query,
	const Context & context,
	const Settings & settings,
	QueryProcessingStage::Enum & processed_stage,
	const size_t max_block_size,
	const unsigned threads)
{
	check(column_names);
	processed_stage = QueryProcessingStage::FetchColumns;

	Block block;

	ColumnWithTypeAndName col_metric;
	col_metric.name = "metric";
	col_metric.type = new DataTypeString;
	col_metric.column = std::make_shared<ColumnString>();
	block.insert(col_metric);

	ColumnWithTypeAndName col_value;
	col_value.name = "value";
	col_value.type = new DataTypeInt64;
	col_value.column = std::make_shared<ColumnInt64>();
	block.insert(col_value);

	for (size_t i = 0; i < CurrentMetrics::END; ++i)
	{
		auto value = CurrentMetrics::values[i];

		col_metric.column->insert(String(CurrentMetrics::getDescription(CurrentMetrics::Metric(i))));
		col_value.column->insert(value);
	}

	return BlockInputStreams(1, new OneBlockInputStream(block));
}


}