MySQL Source code---Core class (1) Thread class

Threading is a very important concept for MySQL. Threads are used to handle connections from clients, and threads and connections are 1:1 off. The thread and the THD object are also 1:1 corresponding relationships, some threads are set to take precedence, while some threads have no priority, and the thread's priority is set to Sql/mysql_priv.h

#define Interrupt_prior-2

#define Connect_prior-1

#define Wait_prior0

#define Query_prior2

(THD is the MySQL thread descriptor Class)

Thread initialization work:

void Thd::init (void)

{

Pthread_mutex_lock (&lock_global_system_variables);

Plugin_thdvar_init (this);

Variables.time_format= date_time_format_copy ((thd*) 0,

Variables.time_format);

Variables.date_format= date_time_format_copy ((thd*) 0,

Variables.date_format);

Variables.datetime_format= date_time_format_copy ((thd*) 0,

Variables.datetime_format);

/*

variables= global_system_variables above has reset

variables.pseudo_thread_id to 0. We need to correct it

Avoid temporary tables replication failure.

*/

Variables.pseudo_thread_id= thread_id;

Pthread_mutex_unlock (&lock_global_system_variables);

Server_status= Server_status_autocommit;

if (Variables.sql_mode & Mode_no_backslash_escapes)

Server_status|= server_status_no_backslash_escapes;

Options= thd_startup_options;

if (variables.max_join_size = = Ha_pos_error)

Options |= option_big_selects;

Else

Options &= ~option_big_selects;

transaction.all.modified_non_trans_table= transaction.stmt.modified_non_trans_table= FALSE;

Open_options=ha_open_options;

update_lock_default= (variables.low_priority_updates?

Tl_write_low_priority:

Tl_write);

session_tx_isolation= (enum_tx_isolation) variables.tx_isolation;

Update_charset ();

Reset_current_stmt_binlog_row_based ();

Bzero (char *) &status_var, sizeof (Status_var));

sql_log_bin_toplevel= Options & Option_bin_log;

#if defined (enabled_debug_sync)

/* Initialize the Debug Sync Facility. See debug_sync.cc. */

Debug_sync_init_thread (this);

#endif/* Defined (enabled_debug_sync) */

}

There are some cleanup and other functions that walk in the file to implement

This article is from the Linux OPS blog, so be sure to keep this source http://2853725.blog.51cto.com/2843725/1544160

MySQL Source---core class (1) thread class