ClickHouse/src/Processors/QueryPlan/ReadFromRemote.cpp

#include <Processors/QueryPlan/ReadFromRemote.h>
#include <Processors/QueryPlan/QueryPlan.h>
#include <Processors/QueryPlan/ExpressionStep.h>
#include <Processors/QueryPlan/Optimizations/QueryPlanOptimizationSettings.h>
#include <QueryPipeline/RemoteQueryExecutor.h>
#include <Parsers/ASTSelectQuery.h>
#include <Parsers/formatAST.h>
#include <Processors/Sources/RemoteSource.h>
#include <Processors/Sources/DelayedSource.h>
#include <Processors/Transforms/ExpressionTransform.h>
#include <Interpreters/ActionsDAG.h>
#include <Interpreters/InterpreterSelectQuery.h>
#include <IO/ConnectionTimeoutsContext.h>
#include <Common/checkStackSize.h>

namespace DB
{

namespace ErrorCodes
{
    extern const int ALL_CONNECTION_TRIES_FAILED;
}

static ActionsDAGPtr getConvertingDAG(const Block & block, const Block & header)
{
    /// Convert header structure to expected.
    /// Also we ignore constants from result and replace it with constants from header.
    /// It is needed for functions like `now64()` or `randConstant()` because their values may be different.
    return ActionsDAG::makeConvertingActions(
        block.getColumnsWithTypeAndName(),
        header.getColumnsWithTypeAndName(),
        ActionsDAG::MatchColumnsMode::Name,
        true);
}

void addConvertingActions(QueryPlan & plan, const Block & header)
{
    if (blocksHaveEqualStructure(plan.getCurrentDataStream().header, header))
        return;

    auto convert_actions_dag = getConvertingDAG(plan.getCurrentDataStream().header, header);
    auto converting = std::make_unique<ExpressionStep>(plan.getCurrentDataStream(), convert_actions_dag);
    plan.addStep(std::move(converting));
}

static void addConvertingActions(Pipe & pipe, const Block & header)
{
    if (blocksHaveEqualStructure(pipe.getHeader(), header))
        return;

    auto convert_actions = std::make_shared<ExpressionActions>(getConvertingDAG(pipe.getHeader(), header));
    pipe.addSimpleTransform([&](const Block & cur_header, Pipe::StreamType) -> ProcessorPtr
    {
        return std::make_shared<ExpressionTransform>(cur_header, convert_actions);
    });
}

static String formattedAST(const ASTPtr & ast)
{
    if (!ast)
        return {};
    WriteBufferFromOwnString buf;
    formatAST(*ast, buf, false, true);
    return buf.str();
}

static std::unique_ptr<QueryPlan> createLocalPlan(
    const ASTPtr & query_ast,
    const Block & header,
    ContextPtr context,
    QueryProcessingStage::Enum processed_stage,
    UInt32 shard_num,
    UInt32 shard_count)
{
    checkStackSize();

    auto query_plan = std::make_unique<QueryPlan>();

    InterpreterSelectQuery interpreter(
        query_ast, context, SelectQueryOptions(processed_stage).setShardInfo(shard_num, shard_count));
    interpreter.buildQueryPlan(*query_plan);

    addConvertingActions(*query_plan, header);

    return query_plan;
}


ReadFromRemote::ReadFromRemote(
    ClusterProxy::IStreamFactory::Shards shards_,
    Block header_,
    QueryProcessingStage::Enum stage_,
    StorageID main_table_,
    ASTPtr table_func_ptr_,
    ContextPtr context_,
    ThrottlerPtr throttler_,
    Scalars scalars_,
    Tables external_tables_,
    Poco::Logger * log_,
    UInt32 shard_count_)
    : ISourceStep(DataStream{.header = std::move(header_)})
    , shards(std::move(shards_))
    , stage(stage_)
    , main_table(std::move(main_table_))
    , table_func_ptr(std::move(table_func_ptr_))
    , context(std::move(context_))
    , throttler(std::move(throttler_))
    , scalars(std::move(scalars_))
    , external_tables(std::move(external_tables_))
    , log(log_)
    , shard_count(shard_count_)
{
}

void ReadFromRemote::addLazyPipe(Pipes & pipes, const ClusterProxy::IStreamFactory::Shard & shard)
{
    bool add_agg_info = stage == QueryProcessingStage::WithMergeableState;
    bool add_totals = false;
    bool add_extremes = false;
    bool async_read = context->getSettingsRef().async_socket_for_remote;
    if (stage == QueryProcessingStage::Complete)
    {
        add_totals = shard.query->as<ASTSelectQuery &>().group_by_with_totals;
        add_extremes = context->getSettingsRef().extremes;
    }

    auto lazily_create_stream = [
            pool = shard.pool, shard_num = shard.shard_num, shard_count = shard_count, query = shard.query, header = shard.header,
            context = context, throttler = throttler,
            main_table = main_table, table_func_ptr = table_func_ptr,
            scalars = scalars, external_tables = external_tables,
            stage = stage, local_delay = shard.local_delay,
            add_agg_info, add_totals, add_extremes, async_read]() mutable
        -> Pipe
    {
        auto current_settings = context->getSettingsRef();
        auto timeouts = ConnectionTimeouts::getTCPTimeoutsWithFailover(
            current_settings).getSaturated(
                current_settings.max_execution_time);
        std::vector<ConnectionPoolWithFailover::TryResult> try_results;
        try
        {
            if (table_func_ptr)
                try_results = pool->getManyForTableFunction(timeouts, &current_settings, PoolMode::GET_MANY);
            else
                try_results = pool->getManyChecked(timeouts, &current_settings, PoolMode::GET_MANY, main_table.getQualifiedName());
        }
        catch (const Exception & ex)
        {
            if (ex.code() == ErrorCodes::ALL_CONNECTION_TRIES_FAILED)
                LOG_WARNING(&Poco::Logger::get("ClusterProxy::SelectStreamFactory"),
                    "Connections to remote replicas of local shard {} failed, will use stale local replica", shard_num);
            else
                throw;
        }

        double max_remote_delay = 0.0;
        for (const auto & try_result : try_results)
        {
            if (!try_result.is_up_to_date)
                max_remote_delay = std::max(try_result.staleness, max_remote_delay);
        }

        if (try_results.empty() || local_delay < max_remote_delay)
        {
            auto plan = createLocalPlan(query, header, context, stage, shard_num, shard_count);
            return QueryPipelineBuilder::getPipe(std::move(*plan->buildQueryPipeline(
                QueryPlanOptimizationSettings::fromContext(context),
                BuildQueryPipelineSettings::fromContext(context))));
        }
        else
        {
            std::vector<IConnectionPool::Entry> connections;
            connections.reserve(try_results.size());
            for (auto & try_result : try_results)
                connections.emplace_back(std::move(try_result.entry));

            String query_string = formattedAST(query);

            scalars["_shard_num"]
                = Block{{DataTypeUInt32().createColumnConst(1, shard_num), std::make_shared<DataTypeUInt32>(), "_shard_num"}};
            auto remote_query_executor = std::make_shared<RemoteQueryExecutor>(
                pool, std::move(connections), query_string, header, context, throttler, scalars, external_tables, stage);

            return createRemoteSourcePipe(remote_query_executor, add_agg_info, add_totals, add_extremes, async_read);
        }
    };

    pipes.emplace_back(createDelayedPipe(shard.header, lazily_create_stream, add_totals, add_extremes));
    pipes.back().addInterpreterContext(context);
    addConvertingActions(pipes.back(), output_stream->header);
}

void ReadFromRemote::addPipe(Pipes & pipes, const ClusterProxy::IStreamFactory::Shard & shard)
{
    bool add_agg_info = stage == QueryProcessingStage::WithMergeableState;
    bool add_totals = false;
    bool add_extremes = false;
    bool async_read = context->getSettingsRef().async_socket_for_remote;
    if (stage == QueryProcessingStage::Complete)
    {
        add_totals = shard.query->as<ASTSelectQuery &>().group_by_with_totals;
        add_extremes = context->getSettingsRef().extremes;
    }

    String query_string = formattedAST(shard.query);

    scalars["_shard_num"]
        = Block{{DataTypeUInt32().createColumnConst(1, shard.shard_num), std::make_shared<DataTypeUInt32>(), "_shard_num"}};
    auto remote_query_executor = std::make_shared<RemoteQueryExecutor>(
        shard.pool, query_string, shard.header, context, throttler, scalars, external_tables, stage);
    remote_query_executor->setLogger(log);

    remote_query_executor->setPoolMode(PoolMode::GET_MANY);
    if (!table_func_ptr)
        remote_query_executor->setMainTable(main_table);

    pipes.emplace_back(createRemoteSourcePipe(remote_query_executor, add_agg_info, add_totals, add_extremes, async_read));
    pipes.back().addInterpreterContext(context);
    addConvertingActions(pipes.back(), output_stream->header);
}

void ReadFromRemote::initializePipeline(QueryPipelineBuilder & pipeline, const BuildQueryPipelineSettings &)
{
    Pipes pipes;
    for (const auto & shard : shards)
    {
        if (shard.lazy)
            addLazyPipe(pipes, shard);
        else
            addPipe(pipes, shard);
    }

    auto pipe = Pipe::unitePipes(std::move(pipes));
    pipeline.init(std::move(pipe));
}

}