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)