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create database explain_test_db;
create table explain_test_db.explain_test_table(c int);
truncate table performance_schema.table_io_waits_summary_by_table;
insert into explain_test_db.explain_test_table values('1');
====================================================================
Testing index for columns OBJECT_TYPE, OBJECT_SCHEMA, OBJECT_NAME
====================================================================
############ Explain for Query ####################################
explain select COUNT_STAR
from performance_schema.table_io_waits_summary_by_table
where OBJECT_TYPE = "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE table_io_waits_summary_by_table NULL ref OBJECT OBJECT 259 const # 100.00 NULL
############ Explain for Query ####################################
explain select COUNT_STAR
from performance_schema.table_io_waits_summary_by_table
where OBJECT_TYPE > "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE table_io_waits_summary_by_table NULL ALL OBJECT NULL NULL NULL # 33.33 Using where
############ Explain for Query ####################################
explain select COUNT_STAR
from performance_schema.table_io_waits_summary_by_table
where OBJECT_TYPE < "2";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE table_io_waits_summary_by_table NULL ALL OBJECT NULL NULL NULL # 33.33 Using where
############ Explain for Query ####################################
explain select COUNT_STAR
from performance_schema.table_io_waits_summary_by_table
where OBJECT_TYPE = "TABLE";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE table_io_waits_summary_by_table NULL ref OBJECT OBJECT 259 const # 100.00 NULL
############ Explain for Query ####################################
explain select COUNT_STAR
from performance_schema.table_io_waits_summary_by_table
where OBJECT_TYPE = "impossible"
and OBJECT_SCHEMA = "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE table_io_waits_summary_by_table NULL ref OBJECT OBJECT 518 const,const # 100.00 NULL
############ Explain for Query ####################################
explain select COUNT_STAR
from performance_schema.table_io_waits_summary_by_table
where OBJECT_TYPE = "TABLE"
and OBJECT_SCHEMA = "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE table_io_waits_summary_by_table NULL ref OBJECT OBJECT 518 const,const # 100.00 NULL
############ Explain for Query ####################################
explain select COUNT_STAR
from performance_schema.table_io_waits_summary_by_table
where OBJECT_TYPE = "TABLE"
and OBJECT_SCHEMA > "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE table_io_waits_summary_by_table NULL ref OBJECT OBJECT 259 const # 33.33 Using where
############ Explain for Query ####################################
explain select COUNT_STAR
from performance_schema.table_io_waits_summary_by_table
where OBJECT_TYPE = "TABLE"
and OBJECT_SCHEMA < "2";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE table_io_waits_summary_by_table NULL ref OBJECT OBJECT 259 const # 33.33 Using where
############ Explain for Query ####################################
explain select COUNT_STAR
from performance_schema.table_io_waits_summary_by_table
where OBJECT_TYPE = "TABLE"
and OBJECT_SCHEMA = "explain_test_db";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE table_io_waits_summary_by_table NULL ref OBJECT OBJECT 518 const,const # 100.00 NULL
############ Explain for Query ####################################
explain select COUNT_STAR
from performance_schema.table_io_waits_summary_by_table
where OBJECT_TYPE = "impossible"
and OBJECT_SCHEMA = "impossible"
and OBJECT_NAME = "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 COUNT_STAR
from performance_schema.table_io_waits_summary_by_table
where OBJECT_TYPE = "TABLE"
and OBJECT_SCHEMA = "explain_test_db"
and OBJECT_NAME = "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 COUNT_STAR
from performance_schema.table_io_waits_summary_by_table
where OBJECT_TYPE = "TABLE"
and OBJECT_SCHEMA = "explain_test_db"
and OBJECT_NAME > "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE table_io_waits_summary_by_table NULL ref OBJECT OBJECT 518 const,const # 33.33 Using where
############ Explain for Query ####################################
explain select COUNT_STAR
from performance_schema.table_io_waits_summary_by_table
where OBJECT_TYPE = "TABLE"
and OBJECT_SCHEMA = "explain_test_db"
and OBJECT_NAME < "2";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE table_io_waits_summary_by_table NULL ref OBJECT OBJECT 518 const,const # 33.33 Using where
############ Explain for Query ####################################
explain select COUNT_STAR
from performance_schema.table_io_waits_summary_by_table
where OBJECT_TYPE = "TABLE"
and OBJECT_SCHEMA = "explain_test_db"
and OBJECT_NAME = "explain_test_table";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE table_io_waits_summary_by_table NULL const OBJECT OBJECT 777 const,const,const # 100.00 NULL
############# Explain End #########################################
flush status;
select COUNT_STAR
from performance_schema.table_io_waits_summary_by_table
where OBJECT_TYPE = "TABLE"
and OBJECT_SCHEMA = "explain_test_db"
and OBJECT_NAME = "explain_test_table";
COUNT_STAR
#
OK: handler_read_key incremented
drop table explain_test_db.explain_test_table;
drop database explain_test_db;
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