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#pragma once
#include <functional>
#include <memory>
namespace DB
{
class QueryPipeline;
class Block;
class Chunk;
class LazyOutputFormat;
struct ProfileInfo;
/// Asynchronous pulling executor for QueryPipeline.
/// Always creates extra thread. If query is executed in single thread, use PullingPipelineExecutor.
/// Typical usage is:
///
/// PullingAsyncPipelineExecutor executor(query_pipeline);
/// while (executor.pull(chunk, timeout))
/// ... process chunk ...
class PullingAsyncPipelineExecutor
{
public:
explicit PullingAsyncPipelineExecutor(QueryPipeline & pipeline_);
~PullingAsyncPipelineExecutor();
/// Get structure of returned block or chunk.
const Block & getHeader() const;
/// Methods return false if query is finished.
/// If milliseconds > 0, returns empty object and `true` after timeout exceeded. Otherwise method is blocking.
/// You can use any pull method.
bool pull(Chunk & chunk, uint64_t milliseconds = 0);
bool pull(Block & block, uint64_t milliseconds = 0);
/// Stop execution of all processors. It is not necessary, but helps to stop execution before executor is destroyed.
void cancel();
/// Stop processors which only read data from source.
void cancelReading();
/// Get totals and extremes. Returns empty chunk if doesn't have any.
Chunk getTotals();
Chunk getExtremes();
/// Get totals and extremes. Returns empty chunk if doesn't have any.
Block getTotalsBlock();
Block getExtremesBlock();
/// Get query profile info.
ProfileInfo & getProfileInfo();
/// Internal executor data.
struct Data;
private:
using CancelFunc = std::function<void()>;
void cancelWithExceptionHandling(CancelFunc && cancel_func);
private:
QueryPipeline & pipeline;
std::shared_ptr<LazyOutputFormat> lazy_format;
std::unique_ptr<Data> data;
};
}
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