Performance Schema events_statements_summary_by_digest Table

The Performance Schema digest is a hashed, normalized form of a statement with the specific data values removed. It allows statistics to be gathered for similar kinds of statements.

The Performance Schema events_statements_summary_by_digest table records statement events summarized by schema and digest. It contains the following columns:

Column	Description
Column	Description
SCHEMA NAME	Database name. Records are summarised together with DIGEST.
DIGEST	Performance Schema digest. Records are summarised together with SCHEMA NAME.
DIGEST TEXT	The unhashed form of the digest.
COUNT_STAR	Number of summarized events
SUM_TIMER_WAIT	Total wait time of the summarized events that are timed.
MIN_TIMER_WAIT	Minimum wait time of the summarized events that are timed.
AVG_TIMER_WAIT	Average wait time of the summarized events that are timed.
MAX_TIMER_WAIT	Maximum wait time of the summarized events that are timed.
SUM_LOCK_TIME	Sum of the LOCK_TIME column in the events_statements_current table.
SUM_ERRORS	Sum of the ERRORS column in the events_statements_current table.
SUM_WARNINGS	Sum of the WARNINGS column in the events_statements_current table.
SUM_ROWS_AFFECTED	Sum of the ROWS_AFFECTED column in the events_statements_current table.
SUM_ROWS_SENT	Sum of the ROWS_SENT column in the events_statements_current table.
SUM_ROWS_EXAMINED	Sum of the ROWS_EXAMINED column in the events_statements_current table.
SUM_CREATED_TMP_DISK_TABLES	Sum of the CREATED_TMP_DISK_TABLES column in the events_statements_current table.
SUM_CREATED_TMP_TABLES	Sum of the CREATED_TMP_TABLES column in the events_statements_current table.
SUM_SELECT_FULL_JOIN	Sum of the SELECT_FULL_JOIN column in the events_statements_current table.
SUM_SELECT_FULL_RANGE_JOIN	Sum of the SELECT_FULL_RANGE_JOIN column in the events_statements_current table.
SUM_SELECT_RANGE	Sum of the SELECT_RANGE column in the events_statements_current table.
SUM_SELECT_RANGE_CHECK	Sum of the SELECT_RANGE_CHECK column in the events_statements_current table.
SUM_SELECT_SCAN	Sum of the SELECT_SCAN column in the events_statements_current table.
SUM_SORT_MERGE_PASSES	Sum of the SORT_MERGE_PASSES column in the events_statements_current table.
SUM_SORT_RANGE	Sum of the SORT_RANGE column in the events_statements_current table.
SUM_SORT_ROWS	Sum of the SORT_ROWS column in the events_statements_current table.
SUM_SORT_SCAN	Sum of the SORT_SCAN column in the events_statements_current table.
SUM_NO_INDEX_USED	Sum of the NO_INDEX_USED column in the events_statements_current table.
SUM_NO_GOOD_INDEX_USED	Sum of the NO_GOOD_INDEX_USED column in the events_statements_current table.
FIRST_SEEN	Time at which the digest was first seen.
LAST_SEEN	Time at which the digest was most recently seen.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

The events_statements_summary_by_digest table is limited in size by the performance_schema_digests_size system variable. Once the limit has been reached and the table is full, all entries are aggregated in a row with a NULL digest. The COUNT_STAR value of this NULL row indicates how many digests are recorded in the row and therefore gives an indication of whether performance_schema_digests_size should be increased to provide more accurate statistics.

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