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 | |
14 | namespace DB |
15 | { |
16 | |
17 | struct Progress; |
18 | |
19 | /** Interface of stream for writing data (into table, filesystem, network, terminal, etc.) |
20 | */ |
21 | class IBlockOutputStream : private boost::noncopyable |
22 | { |
23 | public: |
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 () 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 | |
66 | private: |
67 | std::vector<TableStructureReadLockHolder> table_locks; |
68 | }; |
69 | |
70 | } |
71 | |