IBlockOutputStream.h

#pragma once

#include <boost/noncopyable.hpp>
#include <DB/Storages/IStorage.h>


namespace DB
{

class Block;


/** Interface of stream for writing data (into table, filesystem, network, terminal, etc.)
  */
class IBlockOutputStream : private boost::noncopyable
{
public:
	IBlockOutputStream() {}

	/** 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) {}

	/** Content-Type to set when sending HTTP response.
	  */
	virtual 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 IStorage::TableStructureReadLockPtr & lock) { table_locks.push_back(lock); }

protected:
	IStorage::TableStructureReadLocks table_locks;
};

using BlockOutputStreamPtr = std::shared_ptr<IBlockOutputStream>;

}