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:
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.
© 2019 MariaDB
Licensed under the Creative Commons Attribution 3.0 Unported License and the GNU Free Documentation License.
https://mariadb.com/kb/en/performance-schema-events_statements_summary_by_digest-table/