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create database explain_test_db;
use explain_test_db;
truncate table performance_schema.events_statements_summary_by_digest;
select 1;
1
1
select digest from performance_schema.events_statements_histogram_by_digest
where SCHEMA_NAME = 'explain_test_db' limit 1
into @digest;
use test;
====================================================================
Testing index for columns SCHEMA_NAME, DIGEST, BUCKET_NUMBER
====================================================================
############ Explain for Query ####################################
explain select COUNT_BUCKET
from performance_schema.events_statements_histogram_by_digest
where SCHEMA_NAME = "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_statements_histogram_by_digest NULL ref SCHEMA_NAME SCHEMA_NAME 259 const # 100.00 NULL
############ Explain for Query ####################################
explain select COUNT_BUCKET
from performance_schema.events_statements_histogram_by_digest
where SCHEMA_NAME > "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_statements_histogram_by_digest NULL ALL SCHEMA_NAME NULL NULL NULL # 33.33 Using where
############ Explain for Query ####################################
explain select COUNT_BUCKET
from performance_schema.events_statements_histogram_by_digest
where SCHEMA_NAME < "2";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_statements_histogram_by_digest NULL ALL SCHEMA_NAME NULL NULL NULL # 33.33 Using where
############ Explain for Query ####################################
explain select COUNT_BUCKET
from performance_schema.events_statements_histogram_by_digest
where SCHEMA_NAME = "explain_test_db";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_statements_histogram_by_digest NULL ref SCHEMA_NAME SCHEMA_NAME 259 const # 100.00 NULL
############ Explain for Query ####################################
explain select COUNT_BUCKET
from performance_schema.events_statements_histogram_by_digest
where SCHEMA_NAME = "impossible"
and DIGEST = "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_statements_histogram_by_digest NULL ref SCHEMA_NAME SCHEMA_NAME 518 const,const # 100.00 NULL
############ Explain for Query ####################################
explain select COUNT_BUCKET
from performance_schema.events_statements_histogram_by_digest
where SCHEMA_NAME = "explain_test_db"
and DIGEST = "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_statements_histogram_by_digest NULL ref SCHEMA_NAME SCHEMA_NAME 518 const,const # 100.00 NULL
############ Explain for Query ####################################
explain select COUNT_BUCKET
from performance_schema.events_statements_histogram_by_digest
where SCHEMA_NAME = "explain_test_db"
and DIGEST > "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_statements_histogram_by_digest NULL ref SCHEMA_NAME SCHEMA_NAME 259 const # 33.33 Using where
############ Explain for Query ####################################
explain select COUNT_BUCKET
from performance_schema.events_statements_histogram_by_digest
where SCHEMA_NAME = "explain_test_db"
and DIGEST < "2";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_statements_histogram_by_digest NULL ref SCHEMA_NAME SCHEMA_NAME 259 const # 33.33 Using where
############ Explain for Query ####################################
explain select COUNT_BUCKET
from performance_schema.events_statements_histogram_by_digest
where SCHEMA_NAME = "explain_test_db"
and DIGEST = @digest;
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_statements_histogram_by_digest NULL ref SCHEMA_NAME SCHEMA_NAME 518 const,const # 100.00 NULL
############ Explain for Query ####################################
explain select COUNT_BUCKET
from performance_schema.events_statements_histogram_by_digest
where SCHEMA_NAME = "impossible"
and DIGEST = "impossible"
and BUCKET_NUMBER = "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_BUCKET
from performance_schema.events_statements_histogram_by_digest
where SCHEMA_NAME = "explain_test_db"
and DIGEST = @digest
and BUCKET_NUMBER = "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_statements_histogram_by_digest NULL const SCHEMA_NAME SCHEMA_NAME 522 const,const,const # 100.00 NULL
############ Explain for Query ####################################
explain select COUNT_BUCKET
from performance_schema.events_statements_histogram_by_digest
where SCHEMA_NAME = "explain_test_db"
and DIGEST = @digest
and BUCKET_NUMBER > "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_statements_histogram_by_digest NULL ref SCHEMA_NAME SCHEMA_NAME 518 const,const # 33.33 Using where
############ Explain for Query ####################################
explain select COUNT_BUCKET
from performance_schema.events_statements_histogram_by_digest
where SCHEMA_NAME = "explain_test_db"
and DIGEST = @digest
and BUCKET_NUMBER < "2";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_statements_histogram_by_digest NULL ref SCHEMA_NAME SCHEMA_NAME 518 const,const # 33.33 Using where
############ Explain for Query ####################################
explain select COUNT_BUCKET
from performance_schema.events_statements_histogram_by_digest
where SCHEMA_NAME = "explain_test_db"
and DIGEST = @digest
and BUCKET_NUMBER = 0;
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_statements_histogram_by_digest NULL const SCHEMA_NAME SCHEMA_NAME 522 const,const,const # 100.00 NULL
############# Explain End #########################################
flush status;
select COUNT_BUCKET
from performance_schema.events_statements_histogram_by_digest
where SCHEMA_NAME = "explain_test_db"
and DIGEST = @digest
and BUCKET_NUMBER = 0;
COUNT_BUCKET
#
OK: handler_read_key incremented
drop database explain_test_db;
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