Performance Schema events_statements_summary_by_digest Table

MariaDB starting with 10.0

The events_statements_summary_by_digest table, along with many other new Performance Schema tables, was added in MariaDB 10.0.

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:

ColumnDescription
SCHEMA NAMEDatabase name. Records are summarised together with DIGEST.
DIGESTPerformance Schema digest. Records are summarised together with SCHEMA NAME.
DIGEST TEXTThe unhashed form of the digest.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
SUM_LOCK_TIMESum of the LOCK_TIME column in the events_statements_current table.
SUM_ERRORSSum of the ERRORS column in the events_statements_current table.
SUM_WARNINGSSum of the WARNINGS column in the events_statements_current table.
SUM_ROWS_AFFECTEDSum of the ROWS_AFFECTED column in the events_statements_current table.
SUM_ROWS_SENTSum of the ROWS_SENT column in the events_statements_current table.
SUM_ROWS_EXAMINEDSum of the ROWS_EXAMINED column in the events_statements_current table.
SUM_CREATED_TMP_DISK_TABLESSum of the CREATED_TMP_DISK_TABLES column in the events_statements_current table.
SUM_CREATED_TMP_TABLESSum of the CREATED_TMP_TABLES column in the events_statements_current table.
SUM_SELECT_FULL_JOINSum of the SELECT_FULL_JOIN column in the events_statements_current table.
SUM_SELECT_FULL_RANGE_JOINSum of the SELECT_FULL_RANGE_JOIN column in the events_statements_current table.
SUM_SELECT_RANGESum of the SELECT_RANGE column in the events_statements_current table.
SUM_SELECT_RANGE_CHECKSum of the SELECT_RANGE_CHECK column in the events_statements_current table.
SUM_SELECT_SCANSum of the SELECT_SCAN column in the events_statements_current table.
SUM_SORT_MERGE_PASSESSum of the SORT_MERGE_PASSES column in the events_statements_current table.
SUM_SORT_RANGESum of the SORT_RANGE column in the events_statements_current table.
SUM_SORT_ROWSSum of the SORT_ROWS column in the events_statements_current table.
SUM_SORT_SCANSum of the SORT_SCAN column in the events_statements_current table.
SUM_NO_INDEX_USEDSum of the NO_INDEX_USED column in the events_statements_current table.
SUM_NO_GOOD_INDEX_USEDSum of the NO_GOOD_INDEX_USED column in the events_statements_current table.
FIRST_SEENTime at which the digest was first seen.
LAST_SEENTime 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.

Comments

Comments loading...
Content reproduced on this site is the property of its respective owners, and this content is not reviewed in advance by MariaDB. The views, information and opinions expressed by this content do not necessarily represent those of MariaDB or any other party.