Kill Query

You can cancel currently executing operations or disconnect current connection sessions using the KILL command. This document introduces related operations and considerations.

Getting Query Identifiers

KILL requires a query identifier to cancel the corresponding query request. Query identifiers include: Query ID, Connection ID, and Trace ID.

You can obtain query identifiers through the following methods.

PROCESSLIST

Through the processlist system table, you can get all current session connections and query operations being executed in the connections. This includes the Query ID and Connection ID.

mysql> SHOW PROCESSLIST;
+------------------+------+------+---------------------+---------------------+----------+------+---------+------+-------+-----------------------------------+------------------+---------------+--------------+
| CurrentConnected | Id   | User | Host                | LoginTime           | Catalog  | Db   | Command | Time | State | QueryId                           | Info             | FE            | CloudCluster |
+------------------+------+------+---------------------+---------------------+----------+------+---------+------+-------+-----------------------------------+------------------+---------------+--------------+
| No               |    2 | root | 172.20.32.136:54850 | 2025-05-11 10:41:52 | internal |      | Query   |    6 | OK    | 12ccf7f95c1c4d2c-b03fa9c652757c15 | select sleep(20) | 172.20.32.152 | NULL         |
| Yes              |    3 | root | 172.20.32.136:54862 | 2025-05-11 10:41:55 | internal |      | Query   |    0 | OK    | b710ed990d4144ee-8b15bb53002b7710 | show processlist | 172.20.32.152 | NULL         |
| No               |    1 | root | 172.20.32.136:47964 | 2025-05-11 10:41:54 | internal |      | Sleep   |   11 | EOF   | b60daa992bac4fe4-b29466aacce67d27 |                  | 172.20.32.153 | NULL         |
+------------------+------+------+---------------------+---------------------+----------+------+---------+------+-------+-----------------------------------+------------------+---------------+--------------+

• CurrentConnected: Yes indicates the connection corresponding to the current session.
• Id: The unique identifier of the connection, i.e., Connection ID.
• QueryId: The unique identifier of the Query. Displays the Query Id of the most recently executed or currently executing SQL command.

Note that by default, SHOW PROCESSLIST only displays all session connections on the FE node that the current session is connected to, and does not display session connections from other FE nodes.

If you want to display session connections from all FE nodes, you need to set the following session variable:

SET show_all_fe_connection=true;

Then execute the SHOW PROCESSLIST command again to display session connections from all FE nodes.

You can also view through the system table in information_schema:

SELECT * FROM information_schema.processlist;

By default, processlist displays session connections from all FE nodes without requiring additional settings.

TRACE ID

This feature is supported since versions 2.1.11 and 3.0.7.

By default, the system automatically generates a Query ID for each query. Users need to first obtain the Query ID through the processlist system table before performing a KILL operation.

In addition, users can also customize a Trace ID and perform KILL operations using the Trace ID.

SET session_context = "trace_id:your_trace_id";

Where your_trace_id is the user-defined Trace ID. It can be any string but cannot contain the ; symbol.

Trace ID is a session-level parameter and only applies to the current session. Doris will map subsequent query requests in the current session to this Trace ID.

Kill Requests

The KILL statement supports canceling specified query operations as well as disconnecting specified session connections.

Regular users can cancel queries sent by their own user through the KILL operation. ADMIN users can cancel queries sent by themselves and any other users.

Kill Query

Syntax:

KILL QUERY "query_id" | "trace_id" | connection_id;

KILL QUERY is used to cancel a specified running query operation.

• "query_id"

  The Query ID obtained through the processlist system table. Must be wrapped in quotes. For example:

  KILL QUERY "d36417cc05ff41ab-9d3afe49be251055";

  This operation will attempt to find the Query ID on all FE nodes and cancel the corresponding query.

• "trace_id"

  The Trace ID customized through session_context. Must be wrapped in quotes. For example:

  KILL QUERY "your_trace_id";

  This operation will attempt to find the Trace ID on all FE nodes and cancel the corresponding query.

  This feature is supported since versions 2.1.11 and 3.0.7.

• connection_id

  The Connection ID obtained through the processlist system table. Must be an integer greater than 0 and cannot be wrapped in quotes. For example:

  KILL QUERY 55;

  This operation only applies to session connections on the currently connected FE, and will cancel the query currently being executed on the corresponding session connection.

Kill Connection

Killing a connection will disconnect the specified session connection and also cancel any query operations being executed on the connection.

Syntax:

KILL [CONNECTION] connection_id;

The CONNECTION keyword can be omitted.

• connection_id

  The Connection ID obtained through the processlist system table. Must be an integer greater than 0 and cannot be wrapped in quotes. For example:

  KILL CONNECTION 55;
  KILL 55;

  Connection IDs on different FEs may be the same, but this operation only affects the session connection on the currently connected FE.

Best Practices

1. Implementing query management through custom Trace ID

   Custom Trace IDs allow you to specify unique identifiers for queries in advance, making it easier for management system to implement the [Cancel Query] function. You can customize Trace IDs in the following ways:

   • Set session_context before each query

     Users generate their own Trace ID. It is recommended to use UUID to ensure the uniqueness of the Trace ID.

     SET session_context="trace_id:your_trace_id";
     SELECT * FROM table ...;

   • Add Trace ID in the query statement

     SELECT /*+SET_VAR(session_context=trace_id:your_trace_id)*/ * FROM table ...;

   Afterward, management system can cancel running operations at any time using the Trace ID.