Performance Schema memory_global_by_event_name Table

MariaDB starting with 10.5.2

The memory_summary_global_by_event_name table was introduced in MariaDB 10.5.2.

There are five memory summary tables in the Performance Schema that share a number of fields in common. These include:

The memory_summary_global_by_event_name table contains memory usage statistics aggregated by event and event.

The table contains the following columns:

FieldTypeNullDefaultDescription
EVENT_NAMEvarchar(128)NONULLEvent name.
COUNT_ALLOCbigint(20) unsignedNONULLTotal number of allocations to memory.
COUNT_FREEbigint(20) unsignedNONULLTotal number of attempts to free the allocated memory.
SUM_NUMBER_OF_BYTES_ALLOCbigint(20) unsignedNONULLTotal number of bytes allocated.
SUM_NUMBER_OF_BYTES_FREEbigint(20) unsignedNONULLTotal number of bytes freed
LOW_COUNT_USEDbigint(20)NONULLLowest number of allocated blocks (lowest value of CURRENT_COUNT_USED).
CURRENT_COUNT_USEDbigint(20)NONULLCurrently allocated blocks that have not been freed (COUNT_ALLOC minus COUNT_FREE).
HIGH_COUNT_USEDbigint(20)NONULLHighest number of allocated blocks (highest value of CURRENT_COUNT_USED).
LOW_NUMBER_OF_BYTES_USEDbigint(20)NONULLLowest number of bytes used.
CURRENT_NUMBER_OF_BYTES_USEDbigint(20)NONULLCurrent number of bytes used (total allocated minus total freed).
HIGH_NUMBER_OF_BYTES_USEDbigint(20)NONULLHighest number of bytes used.

Example

Seeing what memory was most often allocated for:

SELECT * FROM memory_summary_global_by_event_name 
  ORDER BY count_alloc DESC LIMIT 1\G
*************************** 1. row ***************************
                  EVENT_NAME: memory/sql/QUICK_RANGE_SELECT::alloc
                 COUNT_ALLOC: 147976
                  COUNT_FREE: 147976
   SUM_NUMBER_OF_BYTES_ALLOC: 600190656
    SUM_NUMBER_OF_BYTES_FREE: 600190656
              LOW_COUNT_USED: 0
          CURRENT_COUNT_USED: 0
             HIGH_COUNT_USED: 68
    LOW_NUMBER_OF_BYTES_USED: 0
CURRENT_NUMBER_OF_BYTES_USED: 0
   HIGH_NUMBER_OF_BYTES_USED: 275808

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