ClickHouse/src/Storages/IStorageCluster.cpp

#include <Storages/IStorageCluster.h>

#include <Common/Exception.h>
#include <Core/QueryProcessingStage.h>
#include <DataTypes/DataTypeString.h>
#include <IO/ConnectionTimeouts.h>
#include <Interpreters/Context.h>
#include <Interpreters/getHeaderForProcessingStage.h>
#include <Interpreters/SelectQueryOptions.h>
#include <Interpreters/InterpreterSelectQuery.h>
#include <Interpreters/AddDefaultDatabaseVisitor.h>
#include <Interpreters/TranslateQualifiedNamesVisitor.h>
#include <Interpreters/InterpreterSelectQueryAnalyzer.h>
#include <Parsers/queryToString.h>
#include <Processors/Sources/NullSource.h>
#include <Processors/Sources/RemoteSource.h>
#include <Processors/QueryPlan/SourceStepWithFilter.h>
#include <QueryPipeline/narrowPipe.h>
#include <QueryPipeline/Pipe.h>
#include <QueryPipeline/RemoteQueryExecutor.h>
#include <QueryPipeline/QueryPipelineBuilder.h>
#include <Storages/IStorage.h>
#include <Storages/SelectQueryInfo.h>
#include <Storages/StorageDictionary.h>

#include <memory>
#include <string>

namespace DB
{

IStorageCluster::IStorageCluster(
    const String & cluster_name_,
    const StorageID & table_id_,
    LoggerPtr log_)
    : IStorage(table_id_)
    , log(log_)
    , cluster_name(cluster_name_)
{
}

class ReadFromCluster : public SourceStepWithFilter
{
public:
    std::string getName() const override { return "ReadFromCluster"; }
    void initializePipeline(QueryPipelineBuilder & pipeline, const BuildQueryPipelineSettings &) override;
    void applyFilters() override;

    ReadFromCluster(
        Block sample_block,
        std::shared_ptr<IStorageCluster> storage_,
        ASTPtr query_to_send_,
        QueryProcessingStage::Enum processed_stage_,
        ClusterPtr cluster_,
        LoggerPtr log_,
        ContextPtr context_)
        : SourceStepWithFilter(DataStream{.header = std::move(sample_block)})
        , storage(std::move(storage_))
        , query_to_send(std::move(query_to_send_))
        , processed_stage(processed_stage_)
        , cluster(std::move(cluster_))
        , log(log_)
        , context(std::move(context_))
    {
    }

private:
    std::shared_ptr<IStorageCluster> storage;
    ASTPtr query_to_send;
    QueryProcessingStage::Enum processed_stage;
    ClusterPtr cluster;
    LoggerPtr log;
    ContextPtr context;

    std::optional<RemoteQueryExecutor::Extension> extension;

    void createExtension(const ActionsDAG::Node * predicate);
    ContextPtr updateSettings(const Settings & settings);
};

void ReadFromCluster::applyFilters()
{
    auto filter_actions_dag = ActionsDAG::buildFilterActionsDAG(filter_nodes.nodes);
    const ActionsDAG::Node * predicate = nullptr;
    if (filter_actions_dag)
        predicate = filter_actions_dag->getOutputs().at(0);

    createExtension(predicate);
}

void ReadFromCluster::createExtension(const ActionsDAG::Node * predicate)
{
    if (extension)
        return;

    extension = storage->getTaskIteratorExtension(predicate, context);
}

/// The code executes on initiator
void IStorageCluster::read(
    QueryPlan & query_plan,
    const Names & column_names,
    const StorageSnapshotPtr & storage_snapshot,
    SelectQueryInfo & query_info,
    ContextPtr context,
    QueryProcessingStage::Enum processed_stage,
    size_t /*max_block_size*/,
    size_t /*num_streams*/)
{
    storage_snapshot->check(column_names);

    updateBeforeRead(context);
    auto cluster = getCluster(context);

    /// Calculate the header. This is significant, because some columns could be thrown away in some cases like query with count(*)

    Block sample_block;
    ASTPtr query_to_send = query_info.query;

    if (context->getSettingsRef().allow_experimental_analyzer)
    {
        sample_block = InterpreterSelectQueryAnalyzer::getSampleBlock(query_info.query, context, SelectQueryOptions(processed_stage));
    }
    else
    {
        auto interpreter = InterpreterSelectQuery(query_info.query, context, SelectQueryOptions(processed_stage).analyze());
        sample_block = interpreter.getSampleBlock();
        query_to_send = interpreter.getQueryInfo().query->clone();
    }

    updateQueryToSendIfNeeded(query_to_send, storage_snapshot, context);

    RestoreQualifiedNamesVisitor::Data data;
    data.distributed_table = DatabaseAndTableWithAlias(*getTableExpression(query_info.query->as<ASTSelectQuery &>(), 0));
    data.remote_table.database = context->getCurrentDatabase();
    data.remote_table.table = getName();
    RestoreQualifiedNamesVisitor(data).visit(query_to_send);
    AddDefaultDatabaseVisitor visitor(context, context->getCurrentDatabase(),
                                      /* only_replace_current_database_function_= */false,
                                      /* only_replace_in_join_= */true);
    visitor.visit(query_to_send);

    auto this_ptr = std::static_pointer_cast<IStorageCluster>(shared_from_this());

    auto reading = std::make_unique<ReadFromCluster>(
        sample_block,
        std::move(this_ptr),
        std::move(query_to_send),
        processed_stage,
        cluster,
        log,
        context);

    query_plan.addStep(std::move(reading));
}

void ReadFromCluster::initializePipeline(QueryPipelineBuilder & pipeline, const BuildQueryPipelineSettings &)
{
    createExtension(nullptr);

    const Scalars & scalars = context->hasQueryContext() ? context->getQueryContext()->getScalars() : Scalars{};
    const bool add_agg_info = processed_stage == QueryProcessingStage::WithMergeableState;

    Pipes pipes;
    auto new_context = updateSettings(context->getSettingsRef());
    const auto & current_settings = new_context->getSettingsRef();
    auto timeouts = ConnectionTimeouts::getTCPTimeoutsWithFailover(current_settings);
    for (const auto & shard_info : cluster->getShardsInfo())
    {
        auto try_results = shard_info.pool->getMany(timeouts, current_settings, PoolMode::GET_MANY);
        for (auto & try_result : try_results)
        {
            auto remote_query_executor = std::make_shared<RemoteQueryExecutor>(
                std::vector<IConnectionPool::Entry>{try_result},
                queryToString(query_to_send),
                getOutputStream().header,
                new_context,
                /*throttler=*/nullptr,
                scalars,
                Tables(),
                processed_stage,
                extension);

            remote_query_executor->setLogger(log);
            pipes.emplace_back(std::make_shared<RemoteSource>(remote_query_executor, add_agg_info, false, false));
        }
    }

    auto pipe = Pipe::unitePipes(std::move(pipes));
    if (pipe.empty())
        pipe = Pipe(std::make_shared<NullSource>(getOutputStream().header));

    for (const auto & processor : pipe.getProcessors())
        processors.emplace_back(processor);

    pipeline.init(std::move(pipe));
}

QueryProcessingStage::Enum IStorageCluster::getQueryProcessingStage(
    ContextPtr context, QueryProcessingStage::Enum to_stage, const StorageSnapshotPtr &, SelectQueryInfo &) const
{
    /// Initiator executes query on remote node.
    if (context->getClientInfo().query_kind == ClientInfo::QueryKind::INITIAL_QUERY)
        if (to_stage >= QueryProcessingStage::Enum::WithMergeableState)
            return QueryProcessingStage::Enum::WithMergeableState;

    /// Follower just reads the data.
    return QueryProcessingStage::Enum::FetchColumns;
}

ContextPtr ReadFromCluster::updateSettings(const Settings & settings)
{
    Settings new_settings = settings;

    /// Cluster table functions should always skip unavailable shards.
    new_settings.skip_unavailable_shards = true;

    auto new_context = Context::createCopy(context);
    new_context->setSettings(new_settings);
    return new_context;
}

ClusterPtr IStorageCluster::getCluster(ContextPtr context) const
{
    return context->getCluster(cluster_name)->getClusterWithReplicasAsShards(context->getSettingsRef());
}

}