80 lines
3.8 KiB
Plaintext
80 lines
3.8 KiB
Plaintext
select connection_id() into @conid;
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select thread_id from performance_schema.threads
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where PROCESSLIST_ID = @conid
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into @tid;
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set @a=1;
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set @b=2;
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set @c=3;
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====================================================================
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Testing index for columns THREAD_ID, 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.user_variables_by_thread
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where THREAD_ID = "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 user_variables_by_thread NULL ref PRIMARY PRIMARY 8 const # 100.00 Using where
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############ Explain for Query ####################################
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explain select VARIABLE_VALUE
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from performance_schema.user_variables_by_thread
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where THREAD_ID > "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 user_variables_by_thread 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.user_variables_by_thread
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where THREAD_ID < "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 user_variables_by_thread 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.user_variables_by_thread
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where THREAD_ID = @tid;
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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 user_variables_by_thread NULL ref PRIMARY PRIMARY 8 const # 100.00 Using where
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############ Explain for Query ####################################
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explain select VARIABLE_VALUE
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from performance_schema.user_variables_by_thread
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where THREAD_ID = "impossible"
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and 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.user_variables_by_thread
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where THREAD_ID = @tid
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and 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.user_variables_by_thread
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where THREAD_ID = @tid
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and 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 user_variables_by_thread NULL ref PRIMARY PRIMARY 8 const # 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.user_variables_by_thread
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where THREAD_ID = @tid
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and 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 user_variables_by_thread NULL ref PRIMARY PRIMARY 8 const # 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.user_variables_by_thread
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where THREAD_ID = @tid
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and VARIABLE_NAME = "a";
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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 user_variables_by_thread NULL const PRIMARY PRIMARY 266 const,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.user_variables_by_thread
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where THREAD_ID = @tid
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and VARIABLE_NAME = "a";
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VARIABLE_VALUE
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#
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OK: handler_read_key incremented
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