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select connection_id() into @conid;
====================================================================
Testing index for columns ID
====================================================================
############ Explain for Query ####################################
explain select ID
from performance_schema.processlist
where 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 ID
from performance_schema.processlist
where ID > "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE processlist NULL ALL PRIMARY NULL NULL NULL # 33.33 Using where
############ Explain for Query ####################################
explain select ID
from performance_schema.processlist
where ID < "2";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE processlist NULL ALL PRIMARY NULL NULL NULL # 33.33 Using where
############ Explain for Query ####################################
explain select ID
from performance_schema.processlist
where ID = @conid;
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE processlist NULL const PRIMARY PRIMARY 8 const # 100.00 NULL
############# Explain End #########################################
flush status;
select ID
from performance_schema.processlist
where ID = @conid;
ID
#
OK: handler_read_key incremented
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