Documentation Home
MySQL 5.7 Reference Manual
Related Documentation Download this Manual
PDF (US Ltr) - 37.9Mb
PDF (A4) - 38.0Mb
PDF (RPM) - 36.5Mb
HTML Download (TGZ) - 9.9Mb
HTML Download (Zip) - 9.9Mb
HTML Download (RPM) - 8.7Mb
Man Pages (TGZ) - 210.0Kb
Man Pages (Zip) - 319.1Kb
Info (Gzip) - 3.5Mb
Info (Zip) - 3.5Mb
Excerpts from this Manual

MySQL 5.7 Reference Manual  /  MySQL Performance Schema  /  Performance Schema Queries

25.5 Performance Schema Queries

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 information to select from the events available after pre-filtering has been applied.

In Section 25.4.3, “Event Pre-Filtering”, an example showed how to pre-filter for file instruments. If the event tables contain both file and nonfile information, post-filtering is another way to see information only for file events. Add a WHERE clause to queries to restrict event selection appropriately:

mysql> SELECT THREAD_ID, NUMBER_OF_BYTES
       FROM performance_schema.events_waits_history
       WHERE EVENT_NAME LIKE 'wait/io/file/%'
       AND NUMBER_OF_BYTES IS NOT NULL;
+-----------+-----------------+
| THREAD_ID | NUMBER_OF_BYTES |
+-----------+-----------------+
|        11 |              66 |
|        11 |              47 |
|        11 |             139 |
|         5 |              24 |
|         5 |             834 |
+-----------+-----------------+

User Comments
User comments in this section are, as the name implies, provided by MySQL users. The MySQL documentation team is not responsible for, nor do they endorse, any of the information provided here.
Sign Up Login You must be logged in to post a comment.