Feed: Planet MySQL
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Author: Frederic Descamps
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Today, yet another blog post about improvements in MySQL 8.0 related to Performance_Schema. Before MySQL 8.0 it was not always easy to get an example of the queries you could find in Performance_Schema when looking for statements summaries. You had to link several tables (even from sys) to achieve this goal as I explained it in this post.

Now in MySQL 8.0, we have changed the table events_statements_summary_by_digest. This table now contains 6 extra columns:

• QUANTILE_95 : stores the 95th percentile of the statement latency, in picoseconds.
• QUANTILE_99 : stores the 99th percentile of the statement latency, in picoseconds.
• QUANTILE_999 : stores the 99.9th percentile of the statement latency, in picoseconds.
• QUERY_SAMPLE_TEXT : captures a query sample that can be used with EXPLAIN to get a query plan.
• QUERY_SAMPLE_SEEN : stores the timestamp of the query.
• QUERY_SAMPLE_TIMER_WAIT : stores the query sample execution time.

FIRST_SEEN and LAST_SEEN have also been modified to use fractional seconds. The previous definition was:

  Field: LAST_SEEN
   Type: timestamp
   Null: NO
    Key: 
Default: 0000-00-00 00:00:00
  Extra: 

Now it’s

  Field: LAST_SEEN
   Type: timestamp(6)
   Null: NO
    Key: 
Default: 0000-00-00 00:00:00.000000
  Extra: 

The main goal is to capture a full example query like it was made in production with some key information about this query example and to make it easily accessible.