ClickHouse/dbms/src/DataStreams/IBlockOutputStream.h
2018-02-23 13:43:24 +03:00

76 lines
2.1 KiB
C++

#pragma once
#include <string>
#include <vector>
#include <memory>
#include <boost/noncopyable.hpp>
#include <Core/Block.h>
namespace DB
{
struct Progress;
class TableStructureReadLock;
using TableStructureReadLockPtr = std::shared_ptr<TableStructureReadLock>;
using TableStructureReadLocks = std::vector<TableStructureReadLockPtr>;
struct Progress;
/** Interface of stream for writing data (into table, filesystem, network, terminal, etc.)
*/
class IBlockOutputStream : private boost::noncopyable
{
public:
IBlockOutputStream() {}
/** Get data structure of the stream in a form of "header" block (it is also called "sample block").
* Header block contains column names, data types, columns of size 0. Constant columns must have corresponding values.
* You must pass blocks of exactly this structure to the 'write' method.
*/
virtual Block getHeader() const = 0;
/** Write block.
*/
virtual void write(const Block & block) = 0;
/** Write or do something before all data or after all data.
*/
virtual void writePrefix() {}
virtual void writeSuffix() {}
/** Flush output buffers if any.
*/
virtual void flush() {}
/** Methods to set additional information for output in formats, that support it.
*/
virtual void setRowsBeforeLimit(size_t /*rows_before_limit*/) {}
virtual void setTotals(const Block & /*totals*/) {}
virtual void setExtremes(const Block & /*extremes*/) {}
/** Notify about progress. Method could be called from different threads.
* Passed value are delta, that must be summarized.
*/
virtual void onProgress(const Progress & /*progress*/) {}
/** Content-Type to set when sending HTTP response.
*/
virtual std::string getContentType() const { return "text/plain; charset=UTF-8"; }
virtual ~IBlockOutputStream() {}
/** Don't let to alter table while instance of stream is alive.
*/
void addTableLock(const TableStructureReadLockPtr & lock) { table_locks.push_back(lock); }
private:
TableStructureReadLocks table_locks;
};
using BlockOutputStreamPtr = std::shared_ptr<IBlockOutputStream>;
}