Performance Schema threads Table
Each server thread is represented as a row in the threads table.
The threads table contains the following columns:
| Column | Description |
|---|---|
THREAD_ID | A unique thread identifier. |
NAME | Name associated with the server's thread instrumentation code, for example thread/sql/main for the server's main() function, and thread/sql/one_connection for a user connection. |
TYPE | FOREGROUND or BACKGROUND, depending on the thread type. User connection threads are FOREGROUND, internal server threads are BACKGROUND. |
PROCESSLIST_ID | The PROCESSLIST.ID value for threads displayed in the INFORMATION_SCHEMA.PROCESSLIST table, or 0 for background threads. Also corresponds with the CONNECTION_ID() return value for the thread. |
PROCESSLIST_USER | Foreground thread user, or NULL for a background thread. |
PROCESSLIST_HOST | Foreground thread host, or NULL for a background thread. |
PROCESSLIST_DB | Thread's default database, or NULL if none exists. |
PROCESSLIST_COMMAND | Type of command executed by the thread. These correspond to the the COM_xxx client/server protocol commands, and the Com_xxx status variables. See Thread Command Values. |
PROCESSLIST_TIME | Time in seconds the thread has been in its current state. |
PROCESSLIST_STATE | Action, event or state indicating what the thread is doing. |
PROCESSLIST_INFO | Statement being executed by the thread, or NULL if a statement is not being executed. If a statement results in calling other statements, such as for a stored procedure, the innermost statement from the stored procedure is shown here. |
PARENT_THREAD_ID | THREAD_ID of the parent thread, if any. Subthreads can for example be spawned as a result of INSERT DELAYED statements. |
ROLE | Unused. |
INSTRUMENTED | YES or NO for Whether the thread is instrumented or not. For foreground threads, the initial value is determined by whether there's a user/host match in the setup_actors table. Subthreads are again matched, while for background threads, this will be set to YES by default. To monitor events that the thread executes, INSTRUMENTED must be YES and the thread_instrumentation consumer in the setup_consumers table must also be YES. |
HISTORY | YES or NO for Whether to log historical events for the thread. For foreground threads, the initial value is determined by whether there's a user/host match in the setup_actors table. Subthreads are again matched, while for background threads, this will be set to YES by default. To monitor events that the thread executes, INSTRUMENTED must be YES and the thread_instrumentation consumer in the setup_consumers table must also be YES. Added in MariaDB 10.5. |
CONNECTION_TYPE | The protocol used to establish the connection. One of TCP/IP, SSL/TLS, Socket, Named Pipe, Shared Memory, or NULL for background threads. Added in MariaDB 10.5. |
THREAD_OS_ID | The thread or task identifier as defined by the underlying operating system, if there is one. Added in MariaDB 10.5 |
Example
SELECT * FROM performance_schema.threads\G;
*************************** 1. row ***************************
THREAD_ID: 1
NAME: thread/sql/main
TYPE: BACKGROUND
PROCESSLIST_ID: NULL
PROCESSLIST_USER: NULL
PROCESSLIST_HOST: NULL
PROCESSLIST_DB: NULL
PROCESSLIST_COMMAND: NULL
PROCESSLIST_TIME: 215859
PROCESSLIST_STATE: Table lock
PROCESSLIST_INFO: INTERNAL DDL LOG RECOVER IN PROGRESS
PARENT_THREAD_ID: NULL
ROLE: NULL
INSTRUMENTED: YES
...
*************************** 21. row ***************************
THREAD_ID: 64
NAME: thread/sql/one_connection
TYPE: FOREGROUND
PROCESSLIST_ID: 44
PROCESSLIST_USER: root
PROCESSLIST_HOST: localhost
PROCESSLIST_DB: NULL
PROCESSLIST_COMMAND: Query
PROCESSLIST_TIME: 0
PROCESSLIST_STATE: Sending data
PROCESSLIST_INFO: SELECT * FROM performance_schema.threads
PARENT_THREAD_ID: NULL
ROLE: NULL
INSTRUMENTED: YES
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