MySQL  8.0.18
Source Code Documentation
dd_schema.h
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22 
23 #ifndef DD_SCHEMA_INCLUDED
24 #define DD_SCHEMA_INCLUDED
25 
26 #include <stddef.h>
27 
28 #include "sql/mdl.h" // enum_mdl_duration
29 
30 class MDL_ticket;
31 class THD;
32 
33 struct CHARSET_INFO;
34 
35 namespace dd {
36 
37 /**
38  Check if given schema exists.
39 
40  @param thd Thread context.
41  @param schema_name Schema to check for.
42  @param [out] exists true if schema exists, else false.
43  @return false if success, true if error.
44 */
45 bool schema_exists(THD *thd, const char *schema_name, bool *exists);
46 
47 /** Create a schema record into dd.schemata. */
48 bool create_schema(THD *thd, const char *schema_name,
50  const bool default_encryption);
51 
52 /**
53  Acquire MDL on schema name.
54  @param thd Thread context.
55  @param schema_name Schema to check for.
56  @param duration Duration type for MDL
57  @param ticket Where to store ticket pointer
58  (default: nullptr, no ticket pointer will be stored)
59  @return false if success, true if error.
60 */
61 bool mdl_lock_schema(THD *thd, const char *schema_name,
62  enum_mdl_duration duration, MDL_ticket **ticket = nullptr);
63 
64 /**
65  RAII based class to acquire and release schema meta data locks.
66 
67  When an instance of this class is created, and 'ensure_lock()' is called,
68  it will acquire an IX lock on the submitted schema name, unless we already
69  have one. When the instance goes out of scope or is deleted, the ticket
70  registered will be released.
71 
72  @note It is vital that the order of releasing and unlocking the schema
73  is correct. The Schema_MDL_locker must always be declared *before*
74  the corresponding Auto_releaser to make sure that the schema locker
75  is deleted *after* the auto releaser. Otherwise, there will be
76  situations where we have the schema object referenced locally, but
77  without a meta data lock. This may, in turn, violate asserts in the
78  shared cache, and open up for improper usage.
79 
80  @todo TODO: Re-design this for a more complete long term solution of
81  this problem. The current solution will mean that e.g. deadlock
82  errors are propagated even when autocommit == 1.
83 */
84 
86  private:
87  THD *m_thd; // Thread context.
88  MDL_ticket *m_ticket; // MDL ticket.
89 
90  public:
92 
93  /**
94  Make sure we have an IX meta data lock on the schema name.
95 
96  If the circumstances indicate that we need a meta data lock, and
97  we do not already have one, then an IX meta data lock is acquired.
98 
99  @param schema_name The name of the schema.
100 
101  @retval true Failed to ensure that the schema name is locked.
102  false It is ensured that we have at least an IX lock on
103  the schema name.
104  */
105 
106  bool ensure_locked(const char *schema_name);
107 
108  /**
109  Release the MDL ticket, if any, when the instance of this
110  class leaves scope or is deleted.
111  */
112 
114 };
115 
116 } // namespace dd
117 #endif // DD_SCHEMA_INCLUDED
A granted metadata lock.
Definition: mdl.h:963
Schema_MDL_locker(THD *thd)
Definition: dd_schema.h:91
MDL_ticket * m_ticket
Definition: dd_schema.h:88
bool ensure_locked(const char *schema_name)
Make sure we have an IX meta data lock on the schema name.
Definition: dd_schema.cc:125
~Schema_MDL_locker()
Release the MDL ticket, if any, when the instance of this class leaves scope or is deleted...
Definition: dd_schema.cc:129
bool schema_exists(THD *thd, const char *schema_name, bool *exists)
Check if given schema exists.
Definition: dd_schema.cc:46
RAII based class to acquire and release schema meta data locks.
Definition: dd_schema.h:85
bool mdl_lock_schema(THD *thd, const char *schema_name, enum_mdl_duration duration, MDL_ticket **ticket)
Acquire MDL on schema name.
Definition: dd_schema.cc:82
static const CHARSET_INFO * charset_info
Definition: mysql.cc:223
Definition: m_ctype.h:359
bool create_schema(THD *thd, const char *schema_name, const CHARSET_INFO *charset_info, bool default_encryption)
Create a schema record into dd.schemata.
Definition: dd_schema.cc:61
THD * m_thd
Definition: dd_schema.h:87
#define NULL
Definition: types.h:55
enum_mdl_duration
Duration of metadata lock.
Definition: mdl.h:316
The version of the current data dictionary table definitions.
Definition: dictionary_client.h:39
static int exists(node_address *name, node_list const *nodes, u_int with_uid)
Definition: node_list.c:108
For each client connection we create a separate thread with THD serving as a thread/connection descri...
Definition: sql_class.h:778