The Ultimate Guide to High Availability with MariaDB

Performance Schema file_instances Table

Description

The file_instances table lists instances of instruments seen by the Performance Schema when executing file I/O instrumentation, and the associated files. Only files that have been opened, and that have not been deleted, will be listed in the table.

The performance_schema_max_file_instances system variable specifies the maximum number of instrumented file objects.

ColumnDescription
FILE_NAMEFile name.
EVENT_NAMEInstrument name associated with the file.
OPEN_COUNTOpen handles on the file. A value of greater than zero means that the file is currently open.

Example

SELECT * FROM performance_schema.file_instances WHERE OPEN_COUNT>0;
+----------------------------------------------------+--------------------------------------+------------+
| FILE_NAME                                          | EVENT_NAME                           | OPEN_COUNT |
+----------------------------------------------------+--------------------------------------+------------+
| /var/log/mysql/mariadb-bin.index                   | wait/io/file/sql/binlog_index        |          1 |
| /var/lib/mysql/ibdata1                             | wait/io/file/innodb/innodb_data_file |          2 |
| /var/lib/mysql/ib_logfile0                         | wait/io/file/innodb/innodb_log_file  |          2 |
| /var/lib/mysql/ib_logfile1                         | wait/io/file/innodb/innodb_log_file  |          2 |
| /var/lib/mysql/mysql/gtid_slave_pos.ibd            | wait/io/file/innodb/innodb_data_file |          3 |
| /var/lib/mysql/mysql/innodb_index_stats.ibd        | wait/io/file/innodb/innodb_data_file |          3 |
| /var/lib/mysql/mysql/innodb_table_stats.ibd        | wait/io/file/innodb/innodb_data_file |          3 |
...

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