introduction
The previous section introduced loading configuration parameters from the command line and configuration files, and this section introduces other initialization logic. The data structures that can be learned include linked lists and hashes. The content that can be paid attention to includes the calculation methods of parameters such as table_def_size/table_cache_size/max_connections/requested_open_files. In addition, if necessary, you can learn performance_schema in depth.
Source code analysis
initialization command
init_sql_statement_names();
The function here is to store the commands in the sql_statement_names global array. For the command types, please refer to my_sqlcommand.h. The enum_sql_command enumeration type is defined here, as follows:
enum enum_sql_command {
SQLCOM_SELECT,
SQLCOM_CREATE_TABLE,
SQLCOM_CREATE_INDEX,
SQLCOM_ALTER_TABLE,
SQLCOM_UPDATE,
SQLCOM_INSERT,
SQLCOM_INSERT_SELECT,
SQLCOM_DELETE,
SQLCOM_TRUNCATE,
SQLCOM_DROP_TABLE,
SQLCOM_DROP_INDEX,
SQLCOM_SHOW_DATABASES,
SQLCOM_SHOW_TABLES,
SQLCOM_SHOW_FIELDS,
SQLCOM_SHOW_KEYS,
SQLCOM_SHOW_VARIABLES,
SQLCOM_SHOW_STATUS,
SQLCOM_SHOW_ENGINE_LOGS,
SQLCOM_SHOW_ENGINE_STATUS,
SQLCOM_SHOW_ENGINE_MUTEX,
SQLCOM_SHOW_PROCESSLIST,
SQLCOM_SHOW_MASTER_STAT,
SQLCOM_SHOW_SLAVE_STAT,
SQLCOM_SHOW_GRANTS,
SQLCOM_SHOW_CREATE,
SQLCOM_SHOW_CHARSETS,
SQLCOM_SHOW_COLLATIONS,
SQLCOM_SHOW_CREATE_DB,
SQLCOM_SHOW_TABLE_STATUS,
SQLCOM_SHOW_TRIGGERS,
SQLCOM_LOAD,
SQLCOM_SET_OPTION,
SQLCOM_LOCK_TABLES,
SQLCOM_UNLOCK_TABLES,
SQLCOM_GRANT,
SQLCOM_CHANGE_DB,
SQLCOM_CREATE_DB,
SQLCOM_DROP_DB,
SQLCOM_ALTER_DB,
SQLCOM_REPAIR,
SQLCOM_REPLACE,
SQLCOM_REPLACE_SELECT,
SQLCOM_CREATE_FUNCTION,
SQLCOM_DROP_FUNCTION,
SQLCOM_REVOKE,
SQLCOM_OPTIMIZE,
SQLCOM_CHECK,
SQLCOM_ASSIGN_TO_KEYCACHE,
SQLCOM_PRELOAD_KEYS,
SQLCOM_FLUSH,
SQLCOM_KILL,
SQLCOM_ANALYZE,
SQLCOM_ROLLBACK,
SQLCOM_ROLLBACK_TO_SAVEPOINT,
SQLCOM_COMMIT,
SQLCOM_SAVEPOINT,
SQLCOM_RELEASE_SAVEPOINT,
SQLCOM_SLAVE_START,
SQLCOM_SLAVE_STOP,
SQLCOM_START_GROUP_REPLICATION,
SQLCOM_STOP_GROUP_REPLICATION,
SQLCOM_BEGIN,
SQLCOM_CHANGE_MASTER,
SQLCOM_CHANGE_REPLICATION_FILTER,
SQLCOM_RENAME_TABLE,
SQLCOM_RESET,
SQLCOM_PURGE,
SQLCOM_PURGE_BEFORE,
SQLCOM_SHOW_BINLOGS,
SQLCOM_SHOW_OPEN_TABLES,
SQLCOM_HA_OPEN,
SQLCOM_HA_CLOSE,
SQLCOM_HA_READ,
SQLCOM_SHOW_SLAVE_HOSTS,
SQLCOM_DELETE_MULTI,
SQLCOM_UPDATE_MULTI,
SQLCOM_SHOW_BINLOG_EVENTS,
SQLCOM_DO,
SQLCOM_SHOW_WARNS,
SQLCOM_EMPTY_QUERY,
SQLCOM_SHOW_ERRORS,
SQLCOM_SHOW_STORAGE_ENGINES,
SQLCOM_SHOW_PRIVILEGES,
SQLCOM_HELP,
SQLCOM_CREATE_USER,
SQLCOM_DROP_USER,
SQLCOM_RENAME_USER,
SQLCOM_REVOKE_ALL,
SQLCOM_CHECKSUM,
SQLCOM_CREATE_PROCEDURE,
SQLCOM_CREATE_SPFUNCTION,
SQLCOM_CALL,
SQLCOM_DROP_PROCEDURE,
SQLCOM_ALTER_PROCEDURE,
SQLCOM_ALTER_FUNCTION,
SQLCOM_SHOW_CREATE_PROC,
SQLCOM_SHOW_CREATE_FUNC,
SQLCOM_SHOW_STATUS_PROC,
SQLCOM_SHOW_STATUS_FUNC,
SQLCOM_PREPARE,
SQLCOM_EXECUTE,
SQLCOM_DEALLOCATE_PREPARE,
SQLCOM_CREATE_VIEW,
SQLCOM_DROP_VIEW,
SQLCOM_CREATE_TRIGGER,
SQLCOM_DROP_TRIGGER,
SQLCOM_XA_START,
SQLCOM_XA_END,
SQLCOM_XA_PREPARE,
SQLCOM_XA_COMMIT,
SQLCOM_XA_ROLLBACK,
SQLCOM_XA_RECOVER,
SQLCOM_SHOW_PROC_CODE,
SQLCOM_SHOW_FUNC_CODE,
SQLCOM_ALTER_TABLESPACE,
SQLCOM_INSTALL_PLUGIN,
SQLCOM_UNINSTALL_PLUGIN,
SQLCOM_BINLOG_BASE64_EVENT,
SQLCOM_SHOW_PLUGINS,
SQLCOM_CREATE_SERVER,
SQLCOM_DROP_SERVER,
SQLCOM_ALTER_SERVER,
SQLCOM_CREATE_EVENT,
SQLCOM_ALTER_EVENT,
SQLCOM_DROP_EVENT,
SQLCOM_SHOW_CREATE_EVENT,
SQLCOM_SHOW_EVENTS,
SQLCOM_SHOW_CREATE_TRIGGER,
SQLCOM_ALTER_DB_UPGRADE,
SQLCOM_SHOW_PROFILE,
SQLCOM_SHOW_PROFILES,
SQLCOM_SIGNAL,
SQLCOM_RESIGNAL,
SQLCOM_SHOW_RELAYLOG_EVENTS,
SQLCOM_GET_DIAGNOSTICS,
SQLCOM_ALTER_USER,
SQLCOM_EXPLAIN_OTHER,
SQLCOM_SHOW_CREATE_USER,
SQLCOM_SHUTDOWN,
SQLCOM_ALTER_INSTANCE,
SQLCOM_END
};
Stored in the array SQLCOM_SELECT corresponds to "select", and SQLCOM_SIGNAL corresponds to "signal". This mapping is taken from the com_status_vars array, and the rest are the same. The only exception is the last SQLCOM_END, which corresponds to "error". The types of sql_statement_names array elements are as follows:
struct st_mysql_const_lex_string
{
const char *str;
size_t length;
};
So in addition to storing the command name, the length of the command name is also recorded.
Initialize system variables
if (my_hash_init(&system_variable_hash, system_charset_info, 100, 0,
0, (my_hash_get_key) get_sys_var_length, 0, HASH_UNIQUE,
PSI_INSTRUMENT_ME))
goto error;
Initialize the hash table system_variable_hash, the structure is as follows:
typedef struct st_hash {
size_t key_offset,key_length;
size_t blength;
ulong records;
uint flags;
DYNAMIC_ARRAY array;
my_hash_get_key get_key;
void (*free)(void *);
CHARSET_INFO *charset;
my_hash_function hash_function;
PSI_memory_key m_psi_key;
} HASH;
size_t is actually long unsigned int type, ulong is unsigned long int type, uint is unsigned int uint type, PSI_memory_key is also unsigned int type, get_key is hash function, free is destructor, CHARSET_INFO *charset is used to store character set, DYNAMIC_ARRAY
array It is a dynamic array with the following structure:
typedef struct st_dynamic_array
{
uchar *buffer;
uint elements,max_element;
uint alloc_increment;
uint size_of_element;
PSI_memory_key m_psi_key;
} DYNAMIC_ARRAY;
Next insert the contents of all_sys_vars into the hash table.
if (mysql_add_sys_var_chain(all_sys_vars.first))
goto error;
Among them, all_sys_vars is a linked list composed of sys_var type, and the head and tail nodes are initialized to NULL, as follows:
sys_var_chain all_sys_vars = { NULL, NULL };
The subclasses of sys_var are declared in sys_vars.h, including Sys_var_integer/Sys_var_typelib/Sys_var_multi_enum/Sys_var_charptr/Sys_var_proxy_user/Sys_var_dbug/Sys_var_double/Sys_var_plugin/Sys_var_debug_sync/Sys_var_have/Sys_var_struct/S ys_var_tz/Sys_var_gtid_next/Sys_var_gtid_set/Sys_var_charptr_func/Sys_var_gtid_purged etc. The data in the all_sys_vars linked list is generated in their constructors. as follows:
Sys_var_integer(const char *name_arg,
const char *comment, int flag_args, ptrdiff_t off, size_t size,
CMD_LINE getopt,
T min_val, T max_val, T def_val, uint block_size, PolyLock *lock=0,
enum binlog_status_enum binlog_status_arg=VARIABLE_NOT_IN_BINLOG,
on_check_function on_check_func=0,
on_update_function on_update_func=0,
const char *substitute=0,
int parse_flag= PARSE_NORMAL)
: sys_var(&all_sys_vars, name_arg, comment, flag_args, off, getopt.id,
getopt.arg_type, SHOWT, def_val, lock, binlog_status_arg,
on_check_func, on_update_func,
substitute, parse_flag)
The system variable object comes from sys_vars.cc, intercept one of them, as follows:
static Sys_var_mybool Sys_pfs_enabled(
"performance_schema",
"Enable the performance schema.",
READ_ONLY GLOBAL_VAR(pfs_param.m_enabled),
CMD_LINE(OPT_ARG), DEFAULT(TRUE),
PFS_TRAILING_PROPERTIES);
Adjustment parameters
adjust_open_files_limit(requested_open_files);
adjust_max_connections(*requested_open_files);
adjust_table_cache_size(*requested_open_files);
adjust_table_def_size();
In adjust_open_files_limit, request_open_files takes the maximum value from the following three calculation formulas. And requested_open_files takes the minimum value of effective_open_files and request_open_files. effective_open_files is calculated as 65536 by default, and request_open_files is calculated as 5000 by default. open_files_limit controls the maximum number of file descriptors that the mysqld process can use, using the value of effective_open_files.
limit_1= 10 + max_connections + table_cache_size * 2;
limit_2= max_connections * 5;
limit_3= open_files_limit ? open_files_limit : 5000;
Next, set max_connections in adjust_max_connections, that is, the maximum number of connections, and take the minimum value of limit and the original value. The limit algorithm is as follows:
limit= requested_open_files - 10 - TABLE_OPEN_CACHE_MIN * 2;
Among them, TABLE_OPEN_CACHE_MIN is 400, so the limit defaults to 4190, and the max_connections usually set is smaller, so it remains unchanged.
limit= max<ulong>((requested_open_files - 10 - max_connections) / 2, TABLE_OPEN_CACHE_MIN);
Set table_cache_size and table_cache_size_per_instance in adjust_table_cache_size. table_cache_size specifies the number of tables that can be opened in memory, similar to max_connections, and takes the minimum value of limit and itself. table_cache_size_per_instance is obtained by dividing table_cache_size by the number of instances.
void adjust_table_def_size()
{
ulong default_value;
sys_var *var;
default_value= min<ulong> (400 + table_cache_size / 2, 2000);
var= intern_find_sys_var(STRING_WITH_LEN("table_definition_cache"));
DBUG_ASSERT(var != NULL);
var->update_default(default_value);
if (! table_definition_cache_specified)
table_def_size= default_value;
}
table_def_size is the number of open table structures in memory. Here, look up the table_definition_cache system variable from the system_variable_hash hash table introduced earlier, and update default_value to option.def_value.
initialize pfs
pfs_param.m_hints.m_table_definition_cache= table_def_size;
pfs_param.m_hints.m_table_open_cache= table_cache_size;
pfs_param.m_hints.m_max_connections= max_connections;
pfs_param.m_hints.m_open_files_limit= requested_open_files;
pfs_param.m_hints.m_max_prepared_stmt_count= max_prepared_stmt_count;
PSI_hook= initialize_performance_schema(&pfs_param);
pfs is performance_schema, which is used to record information such as performance, resources, and wait events during operation. The previously set table_def_size/table_cache_size/max_connections/requested_open_files and other parameters are also set to performance_schema.
Key words
Initialize commands; initialize system variables; adjust parameters; initialize pfs
