76 lines
3.4 KiB
Plaintext
76 lines
3.4 KiB
Plaintext
select FILE_NAME, EVENT_NAME from performance_schema.file_instances
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limit 1
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into @fname, @ename;
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====================================================================
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Testing index for columns FILE_NAME
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====================================================================
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############ Explain for Query ####################################
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explain select count(*)
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from performance_schema.file_instances
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where FILE_NAME = "impossible";
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id select_type table partitions type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE NULL NULL NULL NULL NULL NULL NULL # NULL no matching row in const table
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############ Explain for Query ####################################
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explain select count(*)
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from performance_schema.file_instances
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where FILE_NAME > "impossible";
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id select_type table partitions type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE file_instances NULL ALL PRIMARY NULL NULL NULL # 33.33 Using where
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############ Explain for Query ####################################
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explain select count(*)
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from performance_schema.file_instances
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where FILE_NAME < "2";
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id select_type table partitions type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE file_instances NULL ALL PRIMARY NULL NULL NULL # 33.33 Using where
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############ Explain for Query ####################################
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explain select count(*)
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from performance_schema.file_instances
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where FILE_NAME = @fname;
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id select_type table partitions type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE file_instances NULL const PRIMARY PRIMARY 2050 const # 100.00 NULL
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############# Explain End #########################################
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flush status;
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select count(*)
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from performance_schema.file_instances
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where FILE_NAME = @fname;
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count(*)
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#
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OK: handler_read_key incremented
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====================================================================
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Testing index for columns EVENT_NAME
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====================================================================
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############ Explain for Query ####################################
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explain select count(*)
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from performance_schema.file_instances
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where EVENT_NAME = "impossible";
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id select_type table partitions type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE file_instances NULL ref EVENT_NAME EVENT_NAME 514 const # 100.00 NULL
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############ Explain for Query ####################################
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explain select count(*)
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from performance_schema.file_instances
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where EVENT_NAME > "impossible";
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id select_type table partitions type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE file_instances NULL ALL EVENT_NAME NULL NULL NULL # 33.33 Using where
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############ Explain for Query ####################################
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explain select count(*)
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from performance_schema.file_instances
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where EVENT_NAME < "2";
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id select_type table partitions type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE file_instances NULL ALL EVENT_NAME NULL NULL NULL # 33.33 Using where
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############ Explain for Query ####################################
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explain select count(*)
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from performance_schema.file_instances
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where EVENT_NAME = @ename;
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id select_type table partitions type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE file_instances NULL ref EVENT_NAME EVENT_NAME 514 const # 100.00 NULL
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############# Explain End #########################################
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flush status;
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select count(*)
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from performance_schema.file_instances
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where EVENT_NAME = @ename;
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count(*)
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#
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OK: handler_read_key incremented
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