ClickHouse/dbms/Processors/Pipe.h

#pragma once
#include <Processors/IProcessor.h>
#include <Processors/Sources/SourceWithProgress.h>

namespace DB
{

class Pipe;
using Pipes = std::vector<Pipe>;

class IStorage;
using StoragePtr = std::shared_ptr<IStorage>;

/// Pipe is a set of processors which represents the part of pipeline with single output.
/// All processors in pipe are connected. All ports are connected except the output one.
class Pipe
{
public:
    /// Create from source. It must have no input ports and single output.
    explicit Pipe(ProcessorPtr source);
    /// Connect several pipes together with specified transform.
    /// Transform must have the number of inputs equals to the number of pipes. And single output.
    /// Will connect pipes outputs with transform inputs automatically.
    Pipe(Pipes && pipes, ProcessorPtr transform);

    Pipe(const Pipe & other) = delete;
    Pipe(Pipe && other) = default;

    Pipe & operator=(const Pipe & other) = delete;
    Pipe & operator=(Pipe && other) = default;

    OutputPort & getPort() const { return *output_port; }
    const Block & getHeader() const { return output_port->getHeader(); }

    /// Add transform to pipe. It must have single input and single output (is checked).
    /// Input will be connected with current output port, output port will be updated.
    void addSimpleTransform(ProcessorPtr transform);

    Processors detachProcessors() && { return std::move(processors); }

    /// Specify quotas and limits for every ISourceWithProgress.
    void setLimits(const SourceWithProgress::LocalLimits & limits);
    void setQuota(const std::shared_ptr<const EnabledQuota> & quota);

    /// Set information about preferred executor number for sources.
    void pinSources(size_t executor_number);

    void enableQuota();

    void setTotalsPort(OutputPort * totals_) { totals = totals_; }
    OutputPort * getTotalsPort() const { return totals; }

    size_t maxParallelStreams() const { return max_parallel_streams; }

    /// Do not allow to change the table while the processors of pipe are alive.
    /// TODO: move it to pipeline.
    void addTableLock(const TableStructureReadLockHolder & lock) { table_locks.push_back(lock); }
    /// This methods are from QueryPipeline. Needed to make conversion from pipeline to pipe possible.
    void addInterpreterContext(std::shared_ptr<Context> context) { interpreter_context.emplace_back(std::move(context)); }
    void addStorageHolder(StoragePtr storage) { storage_holders.emplace_back(std::move(storage)); }

    const std::vector<TableStructureReadLockHolder> & getTableLocks() const { return table_locks; }
    const std::vector<std::shared_ptr<Context>> & getContexts() const { return interpreter_context; }
    const std::vector<StoragePtr> & getStorageHolders() const { return storage_holders; }

private:
    Processors processors;
    OutputPort * output_port = nullptr;
    OutputPort * totals = nullptr;

    /// It is the max number of processors which can be executed in parallel for each step. See QueryPipeline::Streams.
    size_t max_parallel_streams = 0;

    std::vector<TableStructureReadLockHolder> table_locks;

    /// Some processors may implicitly use Context or temporary Storage created by Interpreter.
    /// But lifetime of Streams is not nested in lifetime of Interpreters, so we have to store it here,
    /// because QueryPipeline is alive until query is finished.
    std::vector<std::shared_ptr<Context>> interpreter_context;
    std::vector<StoragePtr> storage_holders;

    /// This private constructor is used only from QueryPipeline.
    /// It is not public, because QueryPipeline checks that processors are connected and have single output,
    ///  and therefore we can skip those checks.
    /// Note that Pipe represents a tree if it was created using public interface. But this constructor can't assert it.
    /// So, it's possible that TreeExecutorBlockInputStream could be unable to convert such Pipe to IBlockInputStream.
    explicit Pipe(Processors processors_, OutputPort * output_port, OutputPort * totals);

    friend class QueryPipeline;
};

}