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26.12.17.2 Stage Summary Tables
The Performance Schema maintains tables for collecting current and recent stage events, and aggregates that information in summary tables. Section 26.12.5, “Performance Schema Stage Event Tables” describes the events on which stage summaries are based. See that discussion for information about the content of stage events, the current and historical stage event tables, and how to control stage event collection, which is disabled by default.
Example stage event summary information:
- FROM performance_schema.events_stages_summary_global_by_event_name\G
- ...
- *************************** 5. row ***************************
- EVENT_NAME: stage/sql/checking permissions
- COUNT_STAR: 57
- SUM_TIMER_WAIT: 26501888880
- MIN_TIMER_WAIT: 7317456
- AVG_TIMER_WAIT: 464945295
- MAX_TIMER_WAIT: 12858936792
- ...
- *************************** 9. row ***************************
- COUNT_STAR: 37
- SUM_TIMER_WAIT: 662606568
- MIN_TIMER_WAIT: 1593864
- AVG_TIMER_WAIT: 17907891
- MAX_TIMER_WAIT: 437977248
- ...
Each stage summary table has one or more grouping columns to
indicate how the table aggregates events. Event names refer to
names of event instruments in the
setup_instruments table:
events_stages_summary_by_account_by_event_namehasEVENT_NAME,USER, andHOSTcolumns. Each row summarizes events for a given account (user and host combination) and event name.events_stages_summary_by_host_by_event_namehasEVENT_NAMEandHOSTcolumns. Each row summarizes events for a given host and event name.events_stages_summary_by_thread_by_event_namehasTHREAD_IDandEVENT_NAMEcolumns. Each row summarizes events for a given thread and event name.events_stages_summary_by_user_by_event_namehasEVENT_NAMEandUSERcolumns. Each row summarizes events for a given user and event name.events_stages_summary_global_by_event_namehas anEVENT_NAMEcolumn. Each row summarizes events for a given event name.
Each stage summary table has these summary columns containing
aggregated values: COUNT_STAR,
SUM_TIMER_WAIT,
MIN_TIMER_WAIT,
AVG_TIMER_WAIT, and
MAX_TIMER_WAIT. These columns are analogous
to the columns of the same names in the wait event summary
tables (see Section 26.12.17.1, “Wait Event Summary Tables”), except
that the stage summary tables aggregate events from
events_stages_current rather than
events_waits_current.
The stage summary tables have these indexes:
events_stages_summary_by_account_by_event_name:Primary key on (
USER,HOST,EVENT_NAME)
events_stages_summary_by_host_by_event_name:Primary key on (
HOST,EVENT_NAME)
events_stages_summary_by_thread_by_event_name:Primary key on (
THREAD_ID,EVENT_NAME)
events_stages_summary_by_user_by_event_name:Primary key on (
USER,EVENT_NAME)
events_stages_summary_global_by_event_name:Primary key on (
EVENT_NAME)
TRUNCATE TABLE is permitted for
stage summary tables. It has these effects:
For summary tables not aggregated by account, host, or user, truncation resets the summary columns to zero rather than removing rows.
For summary tables aggregated by account, host, or user, truncation removes rows for accounts, hosts, or users with no connections, and resets the summary columns to zero for the remaining rows.
In addition, each stage summary table that is aggregated by
account, host, user, or thread is implicitly truncated by
truncation of the connection table on which it depends, or
truncation of
events_stages_summary_global_by_event_name.
For details, see
Section 26.12.8, “Performance Schema Connection Tables”.
Document created the 26/06/2006, last modified the 26/10/2018
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