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26.12.17.5 Transaction Summary Tables
The Performance Schema maintains tables for collecting current and recent transaction events, and aggregates that information in summary tables. Section 26.12.7, “Performance Schema Transaction Tables” describes the events on which transaction summaries are based. See that discussion for information about the content of transaction events, the current and historical transaction event tables, and how to control transaction event collection, which is disabled by default.
Example transaction event summary information:
- FROM performance_schema.events_transactions_summary_global_by_event_name
- LIMIT 1\G
- *************************** 1. row ***************************
- EVENT_NAME: transaction
- COUNT_STAR: 5
- SUM_TIMER_WAIT: 19550092000
- MIN_TIMER_WAIT: 2954148000
- AVG_TIMER_WAIT: 3910018000
- MAX_TIMER_WAIT: 5486275000
- COUNT_READ_WRITE: 5
- SUM_TIMER_READ_WRITE: 19550092000
- MIN_TIMER_READ_WRITE: 2954148000
- AVG_TIMER_READ_WRITE: 3910018000
- MAX_TIMER_READ_WRITE: 5486275000
- COUNT_READ_ONLY: 0
- SUM_TIMER_READ_ONLY: 0
- MIN_TIMER_READ_ONLY: 0
- AVG_TIMER_READ_ONLY: 0
- MAX_TIMER_READ_ONLY: 0
Each transaction 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_transactions_summary_by_account_by_event_namehasUSER,HOST, andEVENT_NAMEcolumns. Each row summarizes events for a given account (user and host combination) and event name.events_transactions_summary_by_host_by_event_namehasHOSTandEVENT_NAMEcolumns. Each row summarizes events for a given host and event name.events_transactions_summary_by_thread_by_event_namehasTHREAD_IDandEVENT_NAMEcolumns. Each row summarizes events for a given thread and event name.events_transactions_summary_by_user_by_event_namehasUSERandEVENT_NAMEcolumns. Each row summarizes events for a given user and event name.events_transactions_summary_global_by_event_namehas anEVENT_NAMEcolumn. Each row summarizes events for a given event name.
Each transaction summary table has these summary columns containing aggregated values:
COUNT_STAR,SUM_TIMER_WAIT,MIN_TIMER_WAIT,AVG_TIMER_WAIT,MAX_TIMER_WAITThese 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 transaction summary tables aggregate events from
events_transactions_currentrather thanevents_waits_current. These columns summarize read-write and read-only transactions.COUNT_READ_WRITE,SUM_TIMER_READ_WRITE,MIN_TIMER_READ_WRITE,AVG_TIMER_READ_WRITE,MAX_TIMER_READ_WRITEThese are similar to the
COUNT_STARandxxx_TIMER_WAITCOUNT_READ_ONLY,SUM_TIMER_READ_ONLY,MIN_TIMER_READ_ONLY,AVG_TIMER_READ_ONLY,MAX_TIMER_READ_ONLYThese are similar to the
COUNT_STARandxxx_TIMER_WAIT
The transaction summary tables have these indexes:
events_transactions_summary_by_account_by_event_name:Primary key on (
USER,HOST,EVENT_NAME)
events_transactions_summary_by_host_by_event_name:Primary key on (
HOST,EVENT_NAME)
events_transactions_summary_by_thread_by_event_name:Primary key on (
THREAD_ID,EVENT_NAME)
events_transactions_summary_by_user_by_event_name:Primary key on (
USER,EVENT_NAME)
events_transactions_summary_global_by_event_name:Primary key on (
EVENT_NAME)
TRUNCATE TABLE is permitted for
transaction 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 transaction 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_transactions_summary_global_by_event_name.
For details, see
Section 26.12.8, “Performance Schema Connection Tables”.
Transaction Aggregation Rules
Transaction event collection occurs without regard to isolation level, access mode, or autocommit mode.
Transaction event collection occurs for all non-aborted transactions initiated by the server, including empty transactions.
Read-write transactions are generally more resource intensive than read-only transactions, therefore transaction summary tables include separate aggregate columns for read-write and read-only transactions.
Resource requirements may also vary with transaction isolation level. However, presuming that only one isolation level would be used per server, aggregation by isolation level is not provided.
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Document créé le 26/06/2006, dernière modification le 26/10/2018
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