1#pragma once
2
3#include <ext/shared_ptr_helper.h>
4
5#include <Common/OptimizedRegularExpression.h>
6#include <Storages/IStorage.h>
7
8
9namespace DB
10{
11
12/** A table that represents the union of an arbitrary number of other tables.
13 * All tables must have the same structure.
14 */
15class StorageMerge : public ext::shared_ptr_helper<StorageMerge>, public IStorage
16{
17 friend struct ext::shared_ptr_helper<StorageMerge>;
18public:
19 std::string getName() const override { return "Merge"; }
20 std::string getTableName() const override { return table_name; }
21 std::string getDatabaseName() const override { return database_name; }
22
23 bool isRemote() const override;
24
25 /// The check is delayed to the read method. It checks the support of the tables used.
26 bool supportsSampling() const override { return true; }
27 bool supportsPrewhere() const override { return true; }
28 bool supportsFinal() const override { return true; }
29 bool supportsIndexForIn() const override { return true; }
30
31 /// Consider columns coming from the underlying tables
32 NameAndTypePair getColumn(const String & column_name) const override;
33 bool hasColumn(const String & column_name) const override;
34
35 QueryProcessingStage::Enum getQueryProcessingStage(const Context &) const override;
36
37 BlockInputStreams read(
38 const Names & column_names,
39 const SelectQueryInfo & query_info,
40 const Context & context,
41 QueryProcessingStage::Enum processed_stage,
42 size_t max_block_size,
43 unsigned num_streams) override;
44
45 void rename(const String & /*new_path_to_db*/, const String & new_database_name, const String & new_table_name, TableStructureWriteLockHolder &) override
46 {
47 table_name = new_table_name;
48 database_name = new_database_name;
49 }
50
51
52 void checkAlterIsPossible(const AlterCommands & commands, const Settings & /* settings */) override;
53
54 /// you need to add and remove columns in the sub-tables manually
55 /// the structure of sub-tables is not checked
56 void alter(const AlterCommands & params, const Context & context, TableStructureWriteLockHolder & table_lock_holder) override;
57
58 bool mayBenefitFromIndexForIn(const ASTPtr & left_in_operand, const Context & query_context) const override;
59
60private:
61 String table_name;
62 String database_name;
63 String source_database;
64 OptimizedRegularExpression table_name_regexp;
65 Context global_context;
66
67 using StorageListWithLocks = std::list<std::pair<StoragePtr, TableStructureReadLockHolder>>;
68
69 StorageListWithLocks getSelectedTables(const String & query_id) const;
70
71 StorageMerge::StorageListWithLocks getSelectedTables(const ASTPtr & query, bool has_virtual_column, bool get_lock, const String & query_id) const;
72
73 template <typename F>
74 StoragePtr getFirstTable(F && predicate) const;
75
76 DatabaseTablesIteratorPtr getDatabaseIterator(const Context & context) const;
77
78protected:
79 StorageMerge(
80 const std::string & database_name_,
81 const std::string & table_name_,
82 const ColumnsDescription & columns_,
83 const String & source_database_,
84 const String & table_name_regexp_,
85 const Context & context_);
86
87 Block getQueryHeader(const Names & column_names, const SelectQueryInfo & query_info,
88 const Context & context, QueryProcessingStage::Enum processed_stage);
89
90 BlockInputStreams createSourceStreams(const SelectQueryInfo & query_info, const QueryProcessingStage::Enum & processed_stage,
91 const UInt64 max_block_size, const Block & header, const StoragePtr & storage,
92 const TableStructureReadLockHolder & struct_lock, Names & real_column_names,
93 Context & modified_context, size_t streams_num, bool has_table_virtual_column,
94 bool concat_streams = false);
95
96 void convertingSourceStream(const Block & header, const Context & context, ASTPtr & query,
97 BlockInputStreamPtr & source_stream, QueryProcessingStage::Enum processed_stage);
98};
99
100}
101