MySQL  8.0.27
Source Code Documentation
default_values.h
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22 
23 #ifndef DEFAULT_VALUES_INCLUDED
24 #define DEFAULT_VALUES_INCLUDED
25 
26 #include <stddef.h>
27 
28 #include "my_inttypes.h"
29 
30 /** Forward declarations. */
31 
32 class Create_field;
33 class THD;
34 template <class T>
35 class List;
36 
37 namespace dd {
38 class Column;
39 class Table;
40 } // namespace dd
41 struct TABLE;
42 struct TABLE_SHARE;
43 
44 /**
45  Find the largest field among a list of create fields.
46 
47  Iterates over the list of create fields and find the largest one, i.e.
48  the field with largest pack length.
49 
50  @param create_fields List of create fields.
51  @return Size of the largest field, as number of bytes.
52 */
53 
54 size_t max_pack_length(const List<Create_field> &create_fields);
55 
56 /**
57  Prepare the default value of a single column.
58 
59  This function creates a fake field using the submitted fake table
60  object, which also has assigned a fake table share. The field is
61  create in order to use existing code to store the default value. The
62  value is stored into the submitted buffer, which has been allocated
63  in advance (and will be deleted afterwards). The fake table and
64  share are required by the field infrastructure.
65 
66  After storing the default value into the buffer, the value is read back
67  and copied into the column object's default value field. For bit fields
68  with leftover bits in the preamble, these bits are copied and appended
69  onto the default value as the last byte.
70 
71  @param thd Thread context.
72  @param buf Buffer to store the default value into. The buffer
73  size must be at least two bytes.
74  @param table Fake table to use when storing the default value.
75  @param field Create_field corresponding to the column object.
76  @param [in,out] col_obj Column for which to prepare the default value.
77 
78  @retval true Failure.
79  @retval false Success.
80 */
81 
82 bool prepare_default_value(THD *thd, uchar *buf, TABLE *table,
83  const Create_field &field, dd::Column *col_obj);
84 
85 /**
86  Prepare the default value buffer for an empty record.
87 
88  This function prepares the buffer based on the objects retrieved from the
89  data dictionary. The function will scan the columns of the submitted table
90  objects and calculate the length of the record, the number of null bits,
91  etc. The empty buffer is allocated, and all bits are set to 0, including
92  used null bits, the actual field values, etc. Afterwards, the unused bits
93  in the preamble, up to the next full byte border, are set to 1. Finally,
94  the buffer is assigned to the 'TABLE_SHARE::default_values' field.
95 
96  @note This function does not fill in the actual default values, it just
97  allocates and prepares the buffer.
98 
99  @param thd Thread context.
100  @param table Table for which the default value buffer should
101  be prepared.
102  @param [in,out] share Table share for the table. The default value
103  buffer is assigned to the appropriate table
104  share field.
105 
106  @retval true Failure.
107  @retval false Success.
108 */
109 
111  const dd::Table &table,
112  TABLE_SHARE *share);
113 
114 #endif /* DEFAULT_VALUES_INCLUDED */
Create_field is a description a field/column that may or may not exists in a table.
Definition: create_field.h:50
Definition: sql_list.h:431
For each client connection we create a separate thread with THD serving as a thread/connection descri...
Definition: sql_class.h:821
Definition: column.h:86
Definition: table.h:46
bool prepare_default_value(THD *thd, uchar *buf, TABLE *table, const Create_field &field, dd::Column *col_obj)
Prepare the default value of a single column.
Definition: default_values.cc:188
size_t max_pack_length(const List< Create_field > &create_fields)
Find the largest field among a list of create fields.
Definition: default_values.cc:179
bool prepare_default_value_buffer_and_table_share(THD *thd, const dd::Table &table, TABLE_SHARE *share)
Prepare the default value buffer for an empty record.
Definition: default_values.cc:262
Some integer typedefs for easier portability.
unsigned char uchar
Definition: my_inttypes.h:51
Definition: buf0block_hint.cc:29
The version of the current data dictionary table definitions.
Definition: dictionary_client.h:42
This structure is shared between different table objects.
Definition: table.h:688
Field ** field
Definition: table.h:742
Definition: table.h:1394