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select OBJECT_INSTANCE_BEGIN from performance_schema.file_summary_by_instance limit 1
into @oib;
select FILE_NAME from performance_schema.file_summary_by_instance limit 1
into @fname;
select EVENT_NAME from performance_schema.file_summary_by_instance limit 1
into @ename;
====================================================================
Testing index for columns OBJECT_INSTANCE_BEGIN
====================================================================
############ Explain for Query ####################################
explain select COUNT(*)
from performance_schema.file_summary_by_instance
where OBJECT_INSTANCE_BEGIN = "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 COUNT(*)
from performance_schema.file_summary_by_instance
where OBJECT_INSTANCE_BEGIN > "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE file_summary_by_instance NULL ALL PRIMARY NULL NULL NULL # 33.33 Using where
############ Explain for Query ####################################
explain select COUNT(*)
from performance_schema.file_summary_by_instance
where OBJECT_INSTANCE_BEGIN < "2";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE file_summary_by_instance NULL ALL PRIMARY NULL NULL NULL # 33.33 Using where
############ Explain for Query ####################################
explain select COUNT(*)
from performance_schema.file_summary_by_instance
where OBJECT_INSTANCE_BEGIN = @oib;
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE file_summary_by_instance NULL const PRIMARY PRIMARY 8 const # 100.00 NULL
############# Explain End #########################################
flush status;
select COUNT(*)
from performance_schema.file_summary_by_instance
where OBJECT_INSTANCE_BEGIN = @oib;
COUNT(*)
#
OK: handler_read_key incremented
====================================================================
Testing index for columns FILE_NAME
====================================================================
############ Explain for Query ####################################
explain select COUNT(*)
from performance_schema.file_summary_by_instance
where FILE_NAME = "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE file_summary_by_instance NULL ref FILE_NAME FILE_NAME 2050 const # 100.00 NULL
############ Explain for Query ####################################
explain select COUNT(*)
from performance_schema.file_summary_by_instance
where FILE_NAME > "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE file_summary_by_instance NULL ALL FILE_NAME NULL NULL NULL # 33.33 Using where
############ Explain for Query ####################################
explain select COUNT(*)
from performance_schema.file_summary_by_instance
where FILE_NAME < "2";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE file_summary_by_instance NULL ALL FILE_NAME NULL NULL NULL # 33.33 Using where
############ Explain for Query ####################################
explain select COUNT(*)
from performance_schema.file_summary_by_instance
where FILE_NAME = @fname;
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE file_summary_by_instance NULL ref FILE_NAME FILE_NAME 2050 const # 100.00 NULL
############# Explain End #########################################
flush status;
select COUNT(*)
from performance_schema.file_summary_by_instance
where FILE_NAME = @fname;
COUNT(*)
#
OK: handler_read_key incremented
====================================================================
Testing index for columns EVENT_NAME
====================================================================
############ Explain for Query ####################################
explain select COUNT(*)
from performance_schema.file_summary_by_instance
where EVENT_NAME = "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE file_summary_by_instance NULL ref EVENT_NAME EVENT_NAME 514 const # 100.00 NULL
############ Explain for Query ####################################
explain select COUNT(*)
from performance_schema.file_summary_by_instance
where EVENT_NAME > "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE file_summary_by_instance NULL ALL EVENT_NAME NULL NULL NULL # 33.33 Using where
############ Explain for Query ####################################
explain select COUNT(*)
from performance_schema.file_summary_by_instance
where EVENT_NAME < "2";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE file_summary_by_instance NULL ALL EVENT_NAME NULL NULL NULL # 33.33 Using where
############ Explain for Query ####################################
explain select COUNT(*)
from performance_schema.file_summary_by_instance
where EVENT_NAME = @ename;
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE file_summary_by_instance NULL ref EVENT_NAME EVENT_NAME 514 const # 100.00 NULL
############# Explain End #########################################
flush status;
select COUNT(*)
from performance_schema.file_summary_by_instance
where EVENT_NAME = @ename;
COUNT(*)
#
OK: handler_read_key incremented
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