37 lines
1.7 KiB
Plaintext
37 lines
1.7 KiB
Plaintext
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====================================================================
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Testing index for columns VARIABLE_NAME
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====================================================================
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############ Explain for Query ####################################
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explain select VARIABLE_VALUE
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from performance_schema.global_variables
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where VARIABLE_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 VARIABLE_VALUE
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from performance_schema.global_variables
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where VARIABLE_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 global_variables NULL ALL PRIMARY NULL NULL NULL # 33.33 Using where
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############ Explain for Query ####################################
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explain select VARIABLE_VALUE
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from performance_schema.global_variables
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where VARIABLE_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 global_variables NULL ALL PRIMARY NULL NULL NULL # 33.33 Using where
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############ Explain for Query ####################################
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explain select VARIABLE_VALUE
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from performance_schema.global_variables
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where VARIABLE_NAME = "performance_schema";
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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 global_variables NULL const PRIMARY PRIMARY 258 const # 100.00 NULL
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############# Explain End #########################################
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flush status;
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select VARIABLE_VALUE
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from performance_schema.global_variables
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where VARIABLE_NAME = "performance_schema";
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VARIABLE_VALUE
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#
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OK: handler_read_key incremented
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