Sys Schema sys_config Table

The sys_config table holds persistent configuration options for the Sys Schema, stored using the Aria storage engine to maintain settings across restarts.

Sys Schema is available from MariaDB 10.6.

The sys.sys_config table holds configuration options for the Sys Schema.

This is a persistent table (using the Aria storage engine), with the configuration persisting across upgrades (new options are added with INSERT IGNORE.

The table also has two related triggers, which maintain the user that INSERTs or UPDATEs the configuration - sys_config_insert_set_user and sys_config_update_set_user respectively.

Its structure is as follows:

+----------+--------------+------+-----+-------------------+-----------------------------+
| Field    | Type         | Null | Key | Default           | Extra                       |
+----------+--------------+------+-----+-------------------+-----------------------------+
| variable | varchar(128) | NO   | PRI | NULL              |                             |
| value    | varchar(128) | YES  |     | NULL              |                             |
| set_time | timestamp    | NO   |     | CURRENT_TIMESTAMP | on update CURRENT_TIMESTAMP |
| set_by   | varchar(128) | YES  |     | NULL              |                             |
+----------+--------------+------+-----+-------------------+-----------------------------+

Note, when functions check for configuration options, they first check whether a similar named user variable exists with a value, and if this is not set then pull the configuration option from this table in to that named user variable. This is done for performance reasons (to not continually SELECT from the table), however this comes with the side effect that once inited, the values last with the session, somewhat like how session variables are inited from global variables. If the values within this table are changed, they will not take effect until the user logs in again.

Options Included

Variable	Default Value	Description
statement_truncate_len	64	Sets the size to truncate statements to, for the format_statement function.
statement_performance_analyzer.limit	100	The maximum number of rows to include for the views that does not have a built-in limit (e.g. the 95th percentile view). If not set the limit is 100.
statement_performance_analyzer.view	NULL	Used together with the 'custom' view. If the value contains a space, it is considered a query, otherwise it must be an existing view querying the performance_schema.events_statements_summary_by_digest table.
diagnostics.allow_i_s_tables	OFF	Specifies whether it is allowed to do table scan queries on information_schema.TABLES for the diagnostics procedure.
diagnostics.include_raw	OFF	Set to 'ON' to include the raw data (e.g. the original output of "SELECT * FROM sys.metrics") for the diagnostics procedure.
ps_thread_trx_info.max_length	65535	Sets the maximum output length for JSON object output by the ps_thread_trx_info() function.

Notes

Some early versions of sys_config were stored in InnoDB format.

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