85 lines
3.8 KiB
Plaintext
85 lines
3.8 KiB
Plaintext
create database explain_test_db;
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create table explain_test_db.t1 (c int);
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insert into explain_test_db.t1 values ('1');
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truncate table performance_schema.events_waits_current;
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# Connection 1
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select connection_id() into @conid;
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select * from explain_test_db.t1;
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c
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1
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# Default connection
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====================================================================
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Testing index for columns THREAD_ID, EVENT_ID
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====================================================================
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############ Explain for Query ####################################
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explain select END_EVENT_ID
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from performance_schema.events_waits_current
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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 events_waits_current NULL ref PRIMARY PRIMARY 8 const # 100.00 Using where
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############ Explain for Query ####################################
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explain select END_EVENT_ID
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from performance_schema.events_waits_current
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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 events_waits_current NULL ALL PRIMARY NULL NULL NULL # 33.33 Using where
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############ Explain for Query ####################################
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explain select END_EVENT_ID
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from performance_schema.events_waits_current
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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 events_waits_current NULL ALL PRIMARY NULL NULL NULL # 33.33 Using where
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############ Explain for Query ####################################
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explain select END_EVENT_ID
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from performance_schema.events_waits_current
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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 events_waits_current NULL ref PRIMARY PRIMARY 8 const # 100.00 Using where
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############ Explain for Query ####################################
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explain select END_EVENT_ID
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from performance_schema.events_waits_current
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where THREAD_ID = "impossible"
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and EVENT_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 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 END_EVENT_ID
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from performance_schema.events_waits_current
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where THREAD_ID = @tid
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and EVENT_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 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 END_EVENT_ID
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from performance_schema.events_waits_current
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where THREAD_ID = @tid
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and EVENT_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 events_waits_current NULL ref PRIMARY PRIMARY 8 const # 33.33 Using where
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############ Explain for Query ####################################
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explain select END_EVENT_ID
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from performance_schema.events_waits_current
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where THREAD_ID = @tid
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and EVENT_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 events_waits_current NULL ref PRIMARY PRIMARY 8 const # 33.33 Using where
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############ Explain for Query ####################################
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explain select END_EVENT_ID
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from performance_schema.events_waits_current
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where THREAD_ID = @tid
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and EVENT_ID = @eid;
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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 events_waits_current NULL const PRIMARY PRIMARY 16 const,const # 100.00 NULL
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############# Explain End #########################################
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flush status;
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select END_EVENT_ID
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from performance_schema.events_waits_current
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where THREAD_ID = @tid
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and EVENT_ID = @eid;
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END_EVENT_ID
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#
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OK: handler_read_key incremented
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drop table explain_test_db.t1;
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drop database explain_test_db;
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