1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
|
====================================================================
Testing index for columns EVENT_NAME
====================================================================
############ Explain for Query ####################################
explain select LOW_COUNT_USED
from performance_schema.memory_summary_global_by_event_name
where EVENT_NAME = "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL # NULL no matching row in const table
############ Explain for Query ####################################
explain select LOW_COUNT_USED
from performance_schema.memory_summary_global_by_event_name
where EVENT_NAME > "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE memory_summary_global_by_event_name NULL ALL PRIMARY NULL NULL NULL # 33.33 Using where
############ Explain for Query ####################################
explain select LOW_COUNT_USED
from performance_schema.memory_summary_global_by_event_name
where EVENT_NAME < "2";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE memory_summary_global_by_event_name NULL ALL PRIMARY NULL NULL NULL # 33.33 Using where
############ Explain for Query ####################################
explain select LOW_COUNT_USED
from performance_schema.memory_summary_global_by_event_name
where EVENT_NAME = "memory/performance_schema/users";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE memory_summary_global_by_event_name NULL const PRIMARY PRIMARY 514 const # 100.00 NULL
############# Explain End #########################################
flush status;
select LOW_COUNT_USED
from performance_schema.memory_summary_global_by_event_name
where EVENT_NAME = "memory/performance_schema/users";
LOW_COUNT_USED
#
OK: handler_read_key incremented
|
