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create database explain_test_db;
create table explain_test_db.t1 (c int);
insert into explain_test_db.t1 values ('1');
truncate table performance_schema.events_waits_current;
# Connection 1
select connection_id() into @conid;
select * from explain_test_db.t1;
c
1
# Default connection
====================================================================
Testing index for columns THREAD_ID, EVENT_ID
====================================================================
############ Explain for Query ####################################
explain select END_EVENT_ID
from performance_schema.events_waits_current
where THREAD_ID = "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_waits_current NULL ref PRIMARY PRIMARY 8 const # 100.00 Using where
############ Explain for Query ####################################
explain select END_EVENT_ID
from performance_schema.events_waits_current
where THREAD_ID > "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_waits_current NULL ALL PRIMARY NULL NULL NULL # 33.33 Using where
############ Explain for Query ####################################
explain select END_EVENT_ID
from performance_schema.events_waits_current
where THREAD_ID < "2";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_waits_current NULL ALL PRIMARY NULL NULL NULL # 33.33 Using where
############ Explain for Query ####################################
explain select END_EVENT_ID
from performance_schema.events_waits_current
where THREAD_ID = @tid;
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_waits_current NULL ref PRIMARY PRIMARY 8 const # 100.00 NULL
############ Explain for Query ####################################
explain select END_EVENT_ID
from performance_schema.events_waits_current
where THREAD_ID = "impossible"
and EVENT_ID = "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 END_EVENT_ID
from performance_schema.events_waits_current
where THREAD_ID = @tid
and EVENT_ID = "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 END_EVENT_ID
from performance_schema.events_waits_current
where THREAD_ID = @tid
and EVENT_ID > "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_waits_current NULL ref PRIMARY PRIMARY 8 const # 33.33 Using where
############ Explain for Query ####################################
explain select END_EVENT_ID
from performance_schema.events_waits_current
where THREAD_ID = @tid
and EVENT_ID < "2";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_waits_current NULL ref PRIMARY PRIMARY 8 const # 33.33 Using where
############ Explain for Query ####################################
explain select END_EVENT_ID
from performance_schema.events_waits_current
where THREAD_ID = @tid
and EVENT_ID = @eid;
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_waits_current NULL const PRIMARY PRIMARY 16 const,const # 100.00 NULL
############# Explain End #########################################
flush status;
select END_EVENT_ID
from performance_schema.events_waits_current
where THREAD_ID = @tid
and EVENT_ID = @eid;
END_EVENT_ID
#
OK: handler_read_key incremented
drop table explain_test_db.t1;
drop database explain_test_db;
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