1#pragma once
2
3#include <Core/Block.h>
4#include <DataStreams/IBlockStream_fwd.h>
5#include <Storages/TableStructureLockHolder.h>
6
7#include <boost/noncopyable.hpp>
8
9#include <memory>
10#include <string>
11#include <vector>
12
13
14namespace DB
15{
16
17struct Progress;
18
19/** Interface of stream for writing data (into table, filesystem, network, terminal, etc.)
20 */
21class IBlockOutputStream : private boost::noncopyable
22{
23public:
24 IBlockOutputStream() {}
25
26 /** Get data structure of the stream in a form of "header" block (it is also called "sample block").
27 * Header block contains column names, data types, columns of size 0. Constant columns must have corresponding values.
28 * You must pass blocks of exactly this structure to the 'write' method.
29 */
30 virtual Block getHeader() const = 0;
31
32 /** Write block.
33 */
34 virtual void write(const Block & block) = 0;
35
36 /** Write or do something before all data or after all data.
37 */
38 virtual void writePrefix() {}
39 virtual void writeSuffix() {}
40
41 /** Flush output buffers if any.
42 */
43 virtual void flush() {}
44
45 /** Methods to set additional information for output in formats, that support it.
46 */
47 virtual void setRowsBeforeLimit(size_t /*rows_before_limit*/) {}
48 virtual void setTotals(const Block & /*totals*/) {}
49 virtual void setExtremes(const Block & /*extremes*/) {}
50
51 /** Notify about progress. Method could be called from different threads.
52 * Passed value are delta, that must be summarized.
53 */
54 virtual void onProgress(const Progress & /*progress*/) {}
55
56 /** Content-Type to set when sending HTTP response.
57 */
58 virtual std::string getContentType() const { return "text/plain; charset=UTF-8"; }
59
60 virtual ~IBlockOutputStream() {}
61
62 /** Don't let to alter table while instance of stream is alive.
63 */
64 void addTableLock(const TableStructureReadLockHolder & lock) { table_locks.push_back(lock); }
65
66private:
67 std::vector<TableStructureReadLockHolder> table_locks;
68};
69
70}
71