MySQL 8.0.31
Source Code Documentation
Notices

Topics in this section:

Notices are a way to send axillary data from the server to the client that can be:

  • global
  • local to the current message sequence

Notices don't affect the state of the current message sequence, that means: the client is may ignore notices and still be able to properly understand the message sequence.

Global Notices

Global Notices are sent by the server in case of events happen that are unrelated to the currently active message sequence:

  • server is shutting down
  • replication slave disconnected
  • group replication state change
  • schema or table dropped

Server Shutting Down

The server indicates that it shuts down in a clean way.

Warning
Not supported yet

Replication slave disconnected

The slave stopped to replicate changes from the master/group and may contain stale information.

Note
Checking for SHOW SLAVE STATUS and io_thread and sql_thread leads to a race condition for the following query. One would have to check after query of the slave is still running to see if it didn't stop in between.
Warning
Not supported yet

Group replication state change

Following changes inside the group, trigger this notice: quorum loss, view changed, role of the node changed, state changed. This information is transfered inside GROUP_REPLICATION_STATE_CHANGED notice, using following message Mysqlx::Notice::GroupReplicationStateChanged.

Schema or Table Dropped/Altered/...

If a client maintains a cache of recent queries + resultsets it would improve the caching behavior if the client would be notified if a underlying table or schema was dropped, changed, and so on.

Warning
Not supported yet

Local Notices

Local Notices are related to the currently active Message Sequence like:

Session Variable Changed

Via Mysqlx::Notice::SessionVariableChanged

It allows intermediates to track state changes on the clients session that may be otherwise unnoticeable like:

CREATE PROCEDURE init() BEGIN
SET @@sql_mode=ANSI;
END

Session variable changes are usually done from the client via SET @@... or SELECT @@... := 1, but can also be done via:

  • stored procedures
  • triggers
  • connection setup
    • @@character_set_server
      Note
      Part of this functionality is provided in the MySQL C/S Protocol via WL#4797 SESSION_SYSVAR_TRACKER and the initial handshake packet.

Session State Changed

Via Mysqlx::Notice::SessionStateChanged.

  • Account Expired while Authentication
  • current schema changes: USE ...
  • sever-side generated primary keys (like AUTO_INCREMENT)
  • rows-found, rows-matched, rows-affected
CURRENT_SCHEMA
Sent after statement that changes the current schema like USE ...
Warning
Not supported yet
GENERATED_INSERT_ID
Sent after an ID was created by an INSERT-operation.
Note
Multiple GENERATED_INSERT_ID notices may be sent per message sequence. Stored Procedures, Multi-Row INSERTs, and so on.
ROWS_FOUND
Rows that would be found if LIMIT wasn't applied (see SQL_CALC_FOUND_ROWS)
Warning
Not supported yet
ROWS_AFFECTED
Rows affected by a modifying statement
ROWS_MATCHED
Rows matched by the criteria of a modifying statement (UPDATE, INSERT, DELETE, ...)
Note
ROWS_AFFECTED and ROWS_MATCHED where sent in the MySQL C/S Protocol as plain text info for a OK packet after an UPDATE:
Rows matched: 0 Changed: 0 Warnings: 0
ACCOUNT_EXPIRED
Sent after a successful authentication before Mysqlx::Session::AuthenticateOk
TRX_COMMITTED
Sent after a transaction was committed. .value may contain a transaction identifier.
Note
Used to track implicit, explicit and auto commits.
Warning
Not supported yet
See also
http://dev.mysql.com/doc/en/innodb-implicit-commit.html
TRX_ROLLEDBACK
Sent after a transaction was rolled back.
Note
Used to track implicit and explicit rollback operations.
Warning
Not supported yet
See also
http://dev.mysql.com/doc/en/innodb-implicit-commit.html
SESSION_ID
Sent after a session ID is assigned by the server.
Note
The MySQL C/S provided some of this information via functions:
Parameter Information Functions
CURRENT_SCHEMA DATABASE()
GENERATED_INSERT_ID LAST_INSERT_ID()
ROWS_FOUND FOUND_ROWS()
ROWS_AFFECTED ROW_COUNT()
SESSION_ID CONNECTION_ID()