https://dev.mysql.com/performance-schema-queries.html
Pre-filtering limits which event information is collected and is independent of any particular user. By contrast, post-filtering is performed by individual users through the use of queries with appropriate WHERE clauses that restrict what event ...
https://dev.mysql.com/performance-schema-restrictions.html
If the values in this table for a given timer name are NULL, that timer is not supported on your platform. The Performance Schema avoids using mutexes to collect or produce data, so there are no guarantees of consistency and results can sometimes ...
https://dev.mysql.com/performance-schema-statement-digests.html
If the table becomes full, the Performance Schema groups statements that have SCHEMA_NAME and DIGEST values not matching existing values in the table in a special row with SCHEMA_NAME and DIGEST set to NULL. The MySQL server is capable of ...
https://dev.mysql.com/performance-schema-summary-tables.html
Generally, the effect is to reset the summary columns to 0 or NULL, not to remove rows. Summary tables provide aggregated information for terminated events over time. The tables in this group summarize event data in different ways. Tables that ...
https://dev.mysql.com/performance-schema-table-characteristics.html
Generally, the effect is to reset the summary columns to 0 or NULL, not to remove rows. The name of the performance_schema database is lowercase, as are the names of tables within it. Many tables in the performance_schema database are read only and ...
https://dev.mysql.com/performance-timers-table.html
For an explanation of how event timing occurs, see Section 26.4.1, “Performance Schema Event Timing”. For a cycle timer, the frequency is generally related to the CPU speed. For example, on a system with a 2.4GHz processor, the CYCLE may be ...
https://dev.mysql.com/plugin-loading.html
These can be identified as those that have a library name of NULL in the output from INFORMATION_SCHEMA.PLUGINS or SHOW PLUGINS. Server plugins must be loaded into the server before they can be used. It is also possible to control the activation ...
https://dev.mysql.com/plugins-table.html
If the library name is NULL, the plugin is compiled in and cannot be uninstalled with UNINSTALL PLUGIN. The PLUGINS table has these columns: PLUGIN_NAME The name used to refer to the plugin in statements such as INSTALL PLUGIN and UNINSTALL PLUGIN.
https://dev.mysql.com/point-in-time-recovery-binlog.html
If your binary log contains \0 (null) characters, that output cannot be parsed by mysql unless you invoke it with the --binary-mode option. This section explains the general idea of using the binary log to perform a point-in-time-recovery. The next ...
https://dev.mysql.com/precision-math.html
Similarly, you can treat division by zero as an error rather than as an operation that produces a result of NULL. MySQL provides support for precision math: numeric value handling that results in extremely accurate results and a high degree control ...
