- 24.2.3 C API Function Descriptions
- 24.2.3.1 mysql_affected_rows()
- 24.2.3.2 mysql_autocommit()
- 24.2.3.3 mysql_change_user()
- 24.2.3.4 mysql_character_set_name()
- 24.2.3.5 mysql_close()
- 24.2.3.6 mysql_commit()
- 24.2.3.7 mysql_connect()
- 24.2.3.8 mysql_create_db()
- 24.2.3.9 mysql_data_seek()
- 24.2.3.10 mysql_debug()
- 24.2.3.11 mysql_drop_db()
- 24.2.3.12 mysql_dump_debug_info()
- 24.2.3.13 mysql_eof()
- 24.2.3.14 mysql_errno()
- 24.2.3.15 mysql_error()
- 24.2.3.16 mysql_escape_string()
- 24.2.3.17 mysql_fetch_field()
- 24.2.3.18 mysql_fetch_field_direct()
- 24.2.3.19 mysql_fetch_fields()
- 24.2.3.20 mysql_fetch_lengths()
- 24.2.3.21 mysql_fetch_row()
- 24.2.3.22 mysql_field_count()
- 24.2.3.23 mysql_field_seek()
- 24.2.3.24 mysql_field_tell()
- 24.2.3.25 mysql_free_result()
- 24.2.3.26 mysql_get_character_set_info()
- 24.2.3.27 mysql_get_client_info()
- 24.2.3.28 mysql_get_client_version()
- 24.2.3.29 mysql_get_host_info()
- 24.2.3.30 mysql_get_proto_info()
- 24.2.3.31 mysql_get_server_info()
- 24.2.3.32 mysql_get_server_version()
- 24.2.3.33 mysql_get_ssl_cipher()
- 24.2.3.34 mysql_hex_string()
- 24.2.3.35 mysql_info()
- 24.2.3.36 mysql_init()
- 24.2.3.37 mysql_insert_id()
- 24.2.3.38 mysql_kill()
- 24.2.3.39 mysql_library_end()
- 24.2.3.40 mysql_library_init()
- 24.2.3.41 mysql_list_dbs()
- 24.2.3.42 mysql_list_fields()
- 24.2.3.43 mysql_list_processes()
- 24.2.3.44 mysql_list_tables()
- 24.2.3.45 mysql_more_results()
- 24.2.3.46 mysql_next_result()
- 24.2.3.47 mysql_num_fields()
- 24.2.3.48 mysql_num_rows()
- 24.2.3.49 mysql_options()
- 24.2.3.50 mysql_ping()
- 24.2.3.51 mysql_query()
- 24.2.3.52 mysql_real_connect()
- 24.2.3.53 mysql_real_escape_string()
- 24.2.3.54 mysql_real_query()
- 24.2.3.55 mysql_refresh()
- 24.2.3.56 mysql_reload()
- 24.2.3.57 mysql_rollback()
- 24.2.3.58 mysql_row_seek()
- 24.2.3.59 mysql_row_tell()
- 24.2.3.60 mysql_select_db()
- 24.2.3.61 mysql_set_character_set()
- 24.2.3.62 mysql_set_local_infile_default()
- 24.2.3.63 mysql_set_local_infile_handler()
- 24.2.3.64 mysql_set_server_option()
- 24.2.3.65 mysql_shutdown()
- 24.2.3.66 mysql_sqlstate()
- 24.2.3.67 mysql_ssl_set()
- 24.2.3.68 mysql_stat()
- 24.2.3.69 mysql_store_result()
- 24.2.3.70 mysql_thread_id()
- 24.2.3.71 mysql_use_result()
- 24.2.3.72 mysql_warning_count()
int mysql_ping(MYSQL *mysql)
Description
Checks whether the connection to the server is working. If the connection has gone down, an attempt to reconnect is made unless auto-reconnect is disabled.
This function can be used by clients that remain idle for a long while, to check whether the server has closed the connection and reconnect if necessary.
Return Values
Zero if the connection to the server is alive. Non-zero if an error occurred. A non-zero return does not indicate whether the MySQL server itself is down; the connection might be broken for other reasons such as network problems.
Errors
-
CR_COMMANDS_OUT_OF_SYNCCommands were executed in an improper order.
-
CR_SERVER_GONE_ERRORThe MySQL server has gone away.
-
CR_UNKNOWN_ERRORAn unknown error occurred.
User Comments
An important thing to keep in mind, especially if you're using threads to keep a database connection open/persistant:
A call to mysql_ping, even if the connection never went down, will wipe the results of a mysql_affected_rows, if it somehow occurs between a command execution, and the call.
Symptom: mysql_affected_rows returns -1, when you expect a different number.
(Note - there could be other reasons, this is just one way to guarantee this behavior.)
mysql_ping will only attempt to automatically reconnect if that option has been previously set. As of 5.0.3 the default is to not reconnect.
In order to automatically reconnect, call mysql_options( &mysql, MYSQL_OPT_RECONNECT, ... ) AFTER mysql_real_connect.
Be aware that mysql_ping can cause a SIGPIPE if the connection has idled out. If you aren't expecting a SIGPIPE this can be a little bit of an unpleasant surprize, especially if you're running multithreaded.
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