MySQL  8.0.27
Source Code Documentation
sql_cmd_dml.h
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22 
23 #ifndef SQL_CMD_DML_INCLUDED
24 #define SQL_CMD_DML_INCLUDED
25 
26 #include <assert.h>
27 
28 #include "sql/sql_cmd.h"
29 #include "sql/sql_prepare.h"
30 
31 struct LEX;
32 class Query_result;
33 
34 class Sql_cmd_dml : public Sql_cmd {
35  public:
36  /// @return true if data change statement, false if not (SELECT statement)
37  virtual bool is_data_change_stmt() const { return true; }
38 
39  /**
40  Command-specific resolving (doesn't include LEX::prepare())
41 
42  @param thd Current THD.
43 
44  @returns false on success, true on error
45  */
46  bool prepare(THD *thd) override;
47 
48  /**
49  Execute a DML statement.
50 
51  @param thd thread handler
52 
53  @returns false if success, true if error
54 
55  @details
56  Processing a statement goes through 6 phases (parsing is already done)
57  - Prelocking
58  - Preparation
59  - Locking of tables
60  - Optimization
61  - Execution or explain
62  - Cleanup
63 
64  If the statement is already prepared, this step is skipped.
65 
66  The queries handled by this function are:
67 
68  SELECT
69  INSERT ... SELECT
70  INSERT ... VALUES
71  REPLACE ... SELECT
72  REPLACE ... VALUES
73  UPDATE (single-table and multi-table)
74  DELETE (single-table and multi-table)
75  DO
76 
77  @todo make this function also handle SET.
78  */
79  bool execute(THD *thd) override;
80 
81  bool is_dml() const override { return true; }
82 
83  virtual bool may_use_cursor() const { return false; }
84 
85  bool is_single_table_plan() const override { return false; }
86 
87  /// @return the query result associated with a prepared query
88  Query_result *query_result() const;
89 
90  /// Set query result object for this query statement
92 
93  /// Signal that root result object needs preparing in next execution
94  void set_lazy_result() { m_lazy_result = true; }
95 
96  protected:
98  : Sql_cmd(),
99  lex(nullptr),
100  result(nullptr),
101  m_empty_query(false),
102  m_lazy_result(false) {}
103 
104  /// @return true if query is guaranteed to return no data
105  /**
106  @todo Also check this for the following cases:
107  - Empty source for multi-table UPDATE and DELETE.
108  - Check empty query expression for INSERT
109  */
110  bool is_empty_query() const {
111  assert(is_prepared());
112  return m_empty_query;
113  }
114 
115  /// Set statement as returning no data
116  void set_empty_query() { m_empty_query = true; }
117 
118  /**
119  Perform a precheck of table privileges for the specific operation.
120 
121  @details
122  Check that user has some relevant privileges for all tables involved in
123  the statement, e.g. SELECT privileges for tables selected from, INSERT
124  privileges for tables inserted into, etc. This function will also populate
125  TABLE_LIST::grant with all privileges the user has for each table, which
126  is later used during checking of column privileges.
127  Note that at preparation time, views are not expanded yet. Privilege
128  checking is thus rudimentary and must be complemented with later calls to
129  Query_block::check_view_privileges().
130  The reason to call this function at such an early stage is to be able to
131  quickly reject statements for which the user obviously has insufficient
132  privileges.
133  This function is called before preparing the statement.
134  The function must also be complemented with proper privilege checks for all
135  involved columns (e.g. check_column_grant_*).
136  @see also the function comment of Query_block::prepare().
137  During execution of a prepared statement, call check_privileges() instead.
138 
139  @param thd thread handler
140 
141  @returns false if success, true if false
142  */
143  virtual bool precheck(THD *thd) = 0;
144 
145  /**
146  Check privileges on a prepared statement, called at start of execution
147  of the statement.
148 
149  @details
150  Check that user has all relevant privileges to the statement,
151  ie. INSERT privilege for columns inserted into, UPDATE privilege
152  for columns that are updated, DELETE privilege for tables that are
153  deleted from, SELECT privilege for columns that are referenced, etc.
154 
155  @param thd thread handler
156 
157  @returns false if success, true if false
158  */
159  virtual bool check_privileges(THD *thd) = 0;
160 
161  /**
162  Read and check privileges for all tables in a DML statement.
163 
164  @param thd thread handler
165 
166  @returns false if success, true if false
167 
168  */
169  bool check_all_table_privileges(THD *thd);
170 
171  /**
172  Perform the command-specific parts of DML command preparation,
173  to be called from prepare()
174 
175  @param thd the current thread
176 
177  @returns false if success, true if error
178  */
179  virtual bool prepare_inner(THD *thd) = 0;
180 
181  /**
182  The inner parts of query optimization and execution.
183  Single-table DML operations needs to reimplement this.
184 
185  @param thd Thread handler
186 
187  @returns false on success, true on error
188  */
189  virtual bool execute_inner(THD *thd);
190 
191  /**
192  Restore command properties before execution
193  - Bind metadata for tables and fields
194  - Restore clauses (e.g ORDER BY, GROUP BY) that were destroyed in
195  last optimization.
196  */
197  virtual bool restore_cmd_properties(THD *thd);
198 
199  /// Save command properties, such as prepared query details and table props
200  virtual bool save_cmd_properties(THD *thd);
201 
202  /**
203  Helper function that checks if the command is eligible for secondary engine
204  and if that's true returns the name of that eligible secondary storage
205  engine.
206 
207  @return nullptr if not eligible or the name of the engine otherwise
208  */
210 
211  protected:
212  LEX *lex; ///< Pointer to LEX for this statement
213  Query_result *result; ///< Pointer to object for handling of the result
214  bool m_empty_query; ///< True if query will produce no rows
215  bool m_lazy_result; ///< True: prepare query result on next execution
216 };
217 
218 #endif /* SQL_CMD_DML_INCLUDED */
Definition: query_result.h:55
Definition: sql_cmd_dml.h:34
bool is_empty_query() const
Definition: sql_cmd_dml.h:110
bool is_dml() const override
Definition: sql_cmd_dml.h:81
virtual bool precheck(THD *thd)=0
Perform a precheck of table privileges for the specific operation.
virtual bool prepare_inner(THD *thd)=0
Perform the command-specific parts of DML command preparation, to be called from prepare()
LEX * lex
Pointer to LEX for this statement.
Definition: sql_cmd_dml.h:212
Sql_cmd_dml()
Definition: sql_cmd_dml.h:97
virtual bool may_use_cursor() const
Definition: sql_cmd_dml.h:83
virtual bool is_data_change_stmt() const
Definition: sql_cmd_dml.h:37
void set_empty_query()
Set statement as returning no data.
Definition: sql_cmd_dml.h:116
void set_lazy_result()
Signal that root result object needs preparing in next execution.
Definition: sql_cmd_dml.h:94
bool m_lazy_result
True: prepare query result on next execution.
Definition: sql_cmd_dml.h:215
virtual bool check_privileges(THD *thd)=0
Check privileges on a prepared statement, called at start of execution of the statement.
bool m_empty_query
True if query will produce no rows.
Definition: sql_cmd_dml.h:214
Query_result * result
Pointer to object for handling of the result.
Definition: sql_cmd_dml.h:213
bool is_single_table_plan() const override
Definition: sql_cmd_dml.h:85
Representation of an SQL command.
Definition: sql_cmd.h:64
bool is_prepared() const
Definition: sql_cmd.h:92
For each client connection we create a separate thread with THD serving as a thread/connection descri...
Definition: sql_class.h:821
Dialog Client Authentication nullptr
Definition: dialog.cc:352
bool prepare(THD *thd) override
Command-specific resolving (doesn't include LEX::prepare())
Definition: sql_select.cc:313
bool check_all_table_privileges(THD *thd)
Read and check privileges for all tables in a DML statement.
Definition: sql_select.cc:935
bool execute(THD *thd) override
Execute a DML statement.
Definition: sql_select.cc:483
Query_result * query_result() const
Definition: sql_select.cc:796
void set_query_result(Query_result *result)
Set query result object for this query statement.
Definition: sql_select.cc:803
virtual bool save_cmd_properties(THD *thd)
Save command properties, such as prepared query details and table props.
Definition: sql_select.cc:792
virtual bool restore_cmd_properties(THD *thd)
Restore command properties before execution.
Definition: sql_select.cc:785
const MYSQL_LEX_CSTRING * get_eligible_secondary_engine() const
Helper function that checks if the command is eligible for secondary engine and if that's true return...
Definition: sql_select.cc:972
virtual bool execute_inner(THD *thd)
The inner parts of query optimization and execution.
Definition: sql_select.cc:761
Representation of an SQL command.
The LEX object currently serves three different purposes:
Definition: sql_lex.h:3654
Definition: mysql_lex_string.h:39
Definition: result.h:29