select * from performance_schema.memory_summary_global_by_event_name
where event_name like 'memory/%' limit 1;
select * from performance_schema.memory_summary_global_by_event_name
where event_name='FOO';
insert into performance_schema.memory_summary_global_by_event_name
set event_name='FOO',
count_alloc=1, count_free=2, sum_number_of_bytes_alloc=3,
sum_number_of_bytes_free=4, low_count_used=5;
ERROR 42000: INSERT command denied to user 'root'@'localhost' for table `performance_schema`.`memory_summary_global_by_event_name`
update performance_schema.memory_summary_global_by_event_name
set count_alloc=12;
ERROR 42000: UPDATE command denied to user 'root'@'localhost' for table `performance_schema`.`memory_summary_global_by_event_name`
update performance_schema.memory_summary_global_by_event_name
set count_alloc=12 where event_name like "FOO";
ERROR 42000: UPDATE command denied to user 'root'@'localhost' for table `performance_schema`.`memory_summary_global_by_event_name`
delete from performance_schema.memory_summary_global_by_event_name
where count_alloc=1;
ERROR 42000: DELETE command denied to user 'root'@'localhost' for table `performance_schema`.`memory_summary_global_by_event_name`
delete from performance_schema.memory_summary_global_by_event_name;
ERROR 42000: DELETE command denied to user 'root'@'localhost' for table `performance_schema`.`memory_summary_global_by_event_name`
LOCK TABLES performance_schema.memory_summary_global_by_event_name READ;
ERROR 42000: SELECT, LOCK TABLES command denied to user 'root'@'localhost' for table `performance_schema`.`memory_summary_global_by_event_name`
UNLOCK TABLES;
LOCK TABLES performance_schema.memory_summary_global_by_event_name WRITE;
ERROR 42000: SELECT, LOCK TABLES command denied to user 'root'@'localhost' for table `performance_schema`.`memory_summary_global_by_event_name`
UNLOCK TABLES;
#
# MDEV-25325 column_comment for performance_schema tables
#
select column_name, column_comment 
from information_schema.columns 
where table_schema='performance_schema' and table_name='memory_summary_global_by_event_name';
column_name	column_comment
EVENT_NAME	Event name.
COUNT_ALLOC	Total number of allocations to memory.
COUNT_FREE	Total number of attempts to free the allocated memory.
SUM_NUMBER_OF_BYTES_ALLOC	Total number of bytes allocated.
SUM_NUMBER_OF_BYTES_FREE	Total number of bytes freed
LOW_COUNT_USED	Lowest number of allocated blocks (lowest value of CURRENT_COUNT_USED).
CURRENT_COUNT_USED	Currently allocated blocks that have not been freed (COUNT_ALLOC minus COUNT_FREE).
HIGH_COUNT_USED	Highest number of allocated blocks (highest value of CURRENT_COUNT_USED).
LOW_NUMBER_OF_BYTES_USED	Lowest number of bytes used.
CURRENT_NUMBER_OF_BYTES_USED	Current number of bytes used (total allocated minus total freed).
HIGH_NUMBER_OF_BYTES_USED	Highest number of bytes used.