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

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


namespace DB
{


StorageSystemMetrics::StorageSystemMetrics(const std::string & name_)
    : name(name_)
{
    setColumns(ColumnsDescription({
        {"metric", std::make_shared<DataTypeString>()},
        {"value",  std::make_shared<DataTypeInt64>()},
    }));
}


BlockInputStreams StorageSystemMetrics::read(
    const Names & column_names,
    const SelectQueryInfo &,
    const Context &,
    QueryProcessingStage::Enum & processed_stage,
    const size_t /*max_block_size*/,
    const unsigned /*num_streams*/)
{
    check(column_names);
    processed_stage = QueryProcessingStage::FetchColumns;

    MutableColumns res_columns = getSampleBlock().cloneEmptyColumns();

    for (size_t i = 0, end = CurrentMetrics::end(); i < end; ++i)
    {
        Int64 value = CurrentMetrics::values[i].load(std::memory_order_relaxed);

        res_columns[0]->insert(String(CurrentMetrics::getDescription(CurrentMetrics::Metric(i))));
        res_columns[1]->insert(value);
    }

    return BlockInputStreams(1, std::make_shared<OneBlockInputStream>(getSampleBlock().cloneWithColumns(std::move(res_columns))));
}


}