CLIENT_ERRORS_SUMMARY_BY_USER

The table CLIENT_ERRORS_SUMMARY_BY_USER provides a summary of SQL errors and warnings that have been returned to clients that connect to a TiDB server. These include:

Malformed SQL statements.
Division by zero errors.
The attempt to insert out-of-range or duplicate key values.
Permission errors.
A table that does not exist.

Client errors are returned to the client via the MySQL server protocol, where applications are expected to take appropriate action. The information_schema.CLIENT_ERRORS_SUMMARY_BY_USER table provides an useful method to inspect errors in the scenario where applications are not correctly handling (or logging) errors returned by the TiDB server.

Because CLIENT_ERRORS_SUMMARY_BY_USER summarizes the errors on a per-user basis, it can be useful to diagnose scenarios where one user server is generating more errors than other servers. Possible scenarios include:

Permission errors.
Missing tables, or relational objects.
Incorrect SQL syntax, or incompatibilities between the application and the version of TiDB.

The summarized counts can be reset with the statement FLUSH CLIENT_ERRORS_SUMMARY. The summary is local to each TiDB server and is only retained in memory. Summaries will be lost if the TiDB server restarts.

USE information_schema;
DESC CLIENT_ERRORS_SUMMARY_BY_USER;

+---------------+---------------+------+------+---------+-------+
| Field         | Type          | Null | Key  | Default | Extra |
+---------------+---------------+------+------+---------+-------+
| USER          | varchar(64)   | NO   |      | NULL    |       |
| ERROR_NUMBER  | bigint(64)    | NO   |      | NULL    |       |
| ERROR_MESSAGE | varchar(1024) | NO   |      | NULL    |       |
| ERROR_COUNT   | bigint(64)    | NO   |      | NULL    |       |
| WARNING_COUNT | bigint(64)    | NO   |      | NULL    |       |
| FIRST_SEEN    | timestamp     | YES  |      | NULL    |       |
| LAST_SEEN     | timestamp     | YES  |      | NULL    |       |
+---------------+---------------+------+------+---------+-------+
7 rows in set (0.00 sec)

Field description:

USER: The authenticated user.
ERROR_NUMBER: The MySQL-compatible error number that was returned.
ERROR_MESSAGE: The error message which matches the error number (in prepared statement form).
ERROR_COUNT: The number of times this error was returned to the user.
WARNING_COUNT: The number of times this warning was returned to the user.
FIRST_SEEN: The first time this error (or warning) was sent to the user.
LAST_SEEN: The most recent time this error (or warning) was sent to the user.

The following example shows a warning being generated when the client connects to a local TiDB server. The summary is reset after executing FLUSH CLIENT_ERRORS_SUMMARY:

SELECT 0/0;
SELECT * FROM CLIENT_ERRORS_SUMMARY_BY_USER;
FLUSH CLIENT_ERRORS_SUMMARY;
SELECT * FROM CLIENT_ERRORS_SUMMARY_BY_USER;

+-----+
| 0/0 |
+-----+
| NULL |
+-----+
1 row in set, 1 warning (0.00 sec)

+------+--------------+---------------+-------------+---------------+---------------------+---------------------+
| USER | ERROR_NUMBER | ERROR_MESSAGE | ERROR_COUNT | WARNING_COUNT | FIRST_SEEN          | LAST_SEEN           |
+------+--------------+---------------+-------------+---------------+---------------------+---------------------+
| root |         1365 | Division by 0 |           0 |             1 | 2021-03-18 13:05:36 | 2021-03-18 13:05:36 |
+------+--------------+---------------+-------------+---------------+---------------------+---------------------+
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

Empty set (0.00 sec)