The Ultimate Guide to High Availability with MariaDB

OK_Packet

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Contents

  1. Direction
  2. Fields
  3. Server status flag
  4. Session state info
    1. Session change type
    2. session data's change
      1. SESSION_TRACK_SCHEMA
      2. SESSION_TRACK_SYSTEM_VARIABLES
      3. SESSION_TRACK_STATE_CHANGE
      4. SESSION_TRACK_GTIDS
      5. SESSION_TRACK_TRANSACTION_CHARACTERISTICS
      6. SESSION_TRACK_TRANSACTION_STATE
  5. Notes

OK_Packet is sent by the server to the client and indicates a successful completion of a command sent by the client before.

Direction

Server to client.

Fields


The length-encoded info string is not always included in the packet. Check the length of the packet to detect if there is data after the warning count. For the first OK_Packet in the connection it contains (if present) the SSL certificate verification signature. For the following OK_Packets it contains (if present) various human-readable information.

Server status flag

Values of server status flag

SERVER_STATUS_IN_TRANS1A transaction is currently active
SERVER_STATUS_AUTOCOMMIT2Autocommit mode is set
SERVER_MORE_RESULTS_EXISTS8more results exists (more packet follow)
SERVER_QUERY_NO_GOOD_INDEX_USED16
SERVER_QUERY_NO_INDEX_USED32the query did not use an index
SERVER_STATUS_CURSOR_EXISTS64when using COM_STMT_FETCH, indicate that current cursor still has result
SERVER_STATUS_LAST_ROW_SENT128when using COM_STMT_FETCH, indicate that current cursor has finished to send results
SERVER_STATUS_DB_DROPPED1<<8database has been dropped
SERVER_STATUS_NO_BACKSLASH_ESCAPES1<<9current escape mode is "no backslash escape"
SERVER_STATUS_METADATA_CHANGED1<<10A DDL change did have an impact on an existing PREPARE (an automatic reprepare has been executed)
SERVER_QUERY_WAS_SLOW1<<11the query was slower than long_query_time
SERVER_PS_OUT_PARAMS1<<12this resultset contain stored procedure output parameter
SERVER_STATUS_IN_TRANS_READONLY1<<13current transaction is a read-only transaction
SERVER_SESSION_STATE_CHANGED1<<14session state change. see Session change type for more information


Session state info


Session change type

0SESSION_TRACK_SYSTEM_VARIABLES
1SESSION_TRACK_SCHEMA
2SESSION_TRACK_STATE_CHANGE
3SESSION_TRACK_GTIDS
4SESSION_TRACK_TRANSACTION_CHARACTERISTICS
5SESSION_TRACK_TRANSACTION_STATE


session data's change

Each type of data has his own kind of format :

SESSION_TRACK_SCHEMA
SESSION_TRACK_SYSTEM_VARIABLES

while there is remaining data :

for each variable data :

Possible tracked variables list is tracked by session_track_system_variables

special variable value description:

  • redirect_url: format is `mariadb/mysql:[<user>[:<password>]@]<host>[:<port>]/[<db>[?<opt1>=<value1>[&<opt2>=<value2>]]]`. Possible options:
    • `ttl` : cache timeout in ms to remember redirection, in order to reconnect directly to new host. 0=no caching
SESSION_TRACK_STATE_CHANGE

indicates if session state changes occured. The value is represented as "1".

SESSION_TRACK_GTIDS

This tracker is not implemented by MariaDB.

SESSION_TRACK_TRANSACTION_CHARACTERISTICS

The transaction characteristics is the set of SQL statements that reproduces the type and state of the current transaction. It can consist of the following SQL statements:

SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
SET TRANSACTION ISOLATION LEVEL READ COMMITTED;
SET TRANSACTION ISOLATION LEVEL REPEATABLE READ;
SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;
START TRANSACTION;
START TRANSACTION WITH CONSISTENT SNAPSHOT;
START TRANSACTION WITH CONSISTENT SNAPSHOT, READ ONLY;
START TRANSACTION WITH CONSISTENT SNAPSHOT, READ WRITE;
SET TRANSACTION READ ONLY;
SET TRANSACTION READ WRITE;
XA START <XA specification>;
SESSION_TRACK_TRANSACTION_STATE

The transaction state string is always 8 characters long. The characters, in order, are:

  1. No transaction: _ Explicit transaction: T Implicit transaction: I
  2. Transaction read safe: _ Transaction read unsafe: r
  3. Unknown transaction type: _ Read-only transaction: R
  4. Transaction write safe: _ Transaction write unsafe: w
  5. Unknown transaction type: _ Read-write transaction: W
  6. Transaction statement safe: _ Transaction statement unsafe: s
  7. Transaction does not have resultsets: _ Transaction with resultsets: S
  8. No locked tables: _ Tables have been locked: L

Notes

  • Session tracking is supported from MariaDB 10.2. To determine if session tracking is enabled, check if the CLIENT_SESSION_TRACK flag is set in server_capabilities.

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