26.12.16.3 Statement Summary Tables

events_statements_summary_by_account_by_event_name has EVENT_NAME, USER, and HOST columns. Each row summarizes events for a given account (user and host combination) and event name.

events_statements_summary_by_digest has SCHEMA_NAME and DIGEST columns. Each row summarizes events per schema and digest value. (The DIGEST_TEXT column contains the corresponding normalized statement digest text, but is neither a grouping nor a summary column. The QUERY_SAMPLE_TEXT, QUERY_SAMPLE_SEEN, and QUERY_SAMPLE_TIMER_WAIT columns also are neither grouping nor summary columns; they support statement sampling.)

The maximum number of rows in the table is autosized at server startup. To set this maximum explicitly, set the performance_schema_digests_size system variable at server startup.

events_statements_summary_by_host_by_event_name has EVENT_NAME and HOST columns. Each row summarizes events for a given host and event name.

events_statements_summary_by_program has OBJECT_TYPE, OBJECT_SCHEMA, and OBJECT_NAME columns. Each row summarizes events for a given stored program (stored procedure or function, trigger, or event).

events_statements_summary_by_thread_by_event_name has THREAD_ID and EVENT_NAME columns. Each row summarizes events for a given thread and event name.

events_statements_summary_by_user_by_event_name has EVENT_NAME and USER columns. Each row summarizes events for a given user and event name.

events_statements_summary_global_by_event_name has an EVENT_NAME column. Each row summarizes events for a given event name.

prepared_statements_instances has an OBJECT_INSTANCE_BEGIN column. Each row summarizes events for a given prepared statement.

COUNT_STAR, SUM_TIMER_WAIT, MIN_TIMER_WAIT, AVG_TIMER_WAIT, MAX_TIMER_WAIT

These columns are analogous to the columns of the same names in the wait event summary tables (see Section 26.12.16.1, “Wait Event Summary Tables”), except that the statement summary tables aggregate events from events_statements_current rather than events_waits_current.

The prepared_statements_instances table does not have these columns.

SUM_xxx

The aggregate of the corresponding xxx column in the events_statements_current table. For example, the SUM_LOCK_TIME and SUM_ERRORS columns in statement summary tables are the aggregates of the LOCK_TIME and ERRORS columns in events_statements_current table.

FIRST_SEEN, LAST_SEEN

Timestamps indicating when statements with the given digest value were first seen and most recently seen.

QUANTILE_95: The 95th percentile of the statement latency, in picoseconds. This percentile is a high estimate, computed from the histogram data collected. In other words, for a given digest, 95% of the statements measured have a latency lower than QUANTILE_95.

For access to the histogram data, use the tables described in Section 26.12.16.4, “Statement Histogram Summary Tables”.

QUANTILE_99: Similar to QUANTILE_95, but for the 99th percentile.

QUANTILE_999: Similar to QUANTILE_95, but for the 99.9th percentile.

QUERY_SAMPLE_TEXT

A sample SQL statement that produces the digest value in the row. This column enables applications to access, for a given digest value, a statement actually seen by the server that produces that digest. One use for this might be to run EXPLAIN on the statement to examine the execution plan for a representative statement associated with a frequently occurring digest.

When the QUERY_SAMPLE_TEXT column is assigned a value, the QUERY_SAMPLE_SEEN and QUERY_SAMPLE_TIMER_WAIT columns are assigned values as well.

The maximum space available for statement display is 1024 bytes by default. To change this value, set the performance_schema_max_sql_text_length system variable at server startup. (Changing this value affects columns in other Performance Schema tables as well. See Section 26.10, “Performance Schema Statement Digests and Sampling”.)

For information about statement sampling, see Section 26.10, “Performance Schema Statement Digests and Sampling”.

QUERY_SAMPLE_SEEN

A timestamp indicating when the statement in the QUERY_SAMPLE_TEXT column was seen.

QUERY_SAMPLE_TIMER_WAIT

The wait time for the sample statement in the QUERY_SAMPLE_TEXT column.

COUNT_STATEMENTS, SUM_STATEMENTS_WAIT, MIN_STATEMENTS_WAIT, AVG_STATEMENTS_WAIT, MAX_STATEMENTS_WAIT

Statistics about nested statements invoked during stored program execution.

COUNT_EXECUTE, SUM_TIMER_EXECUTE, MIN_TIMER_EXECUTE, AVG_TIMER_EXECUTE, MAX_TIMER_EXECUTE

Aggregated statistics for executions of the prepared statement.

events_transactions_summary_by_account_by_event_name:

events_statements_summary_by_digest:

events_transactions_summary_by_host_by_event_name:

events_statements_summary_by_program:

events_statements_summary_by_thread_by_event_name:

events_transactions_summary_by_user_by_event_name:

events_statements_summary_global_by_event_name:

For events_statements_summary_by_digest, it removes the rows.

For other summary tables not aggregated by account, host, or user, truncation resets the summary columns to zero rather than removing rows.

For other 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.