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create database explain_test_db;
use explain_test_db;
select 1;
1
1
use test;
====================================================================
Testing index for columns BUCKET_NUMBER
====================================================================
############ Explain for Query ####################################
explain select COUNT_BUCKET
from performance_schema.events_statements_histogram_global
where BUCKET_NUMBER = "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_statements_histogram_global NULL const PRIMARY PRIMARY 4 const # 100.00 NULL
############ Explain for Query ####################################
explain select COUNT_BUCKET
from performance_schema.events_statements_histogram_global
where BUCKET_NUMBER > "impossible";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_statements_histogram_global NULL ALL PRIMARY NULL NULL NULL # 33.33 Using where
############ Explain for Query ####################################
explain select COUNT_BUCKET
from performance_schema.events_statements_histogram_global
where BUCKET_NUMBER < "2";
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_statements_histogram_global NULL ALL PRIMARY NULL NULL NULL # 33.33 Using where
############ Explain for Query ####################################
explain select COUNT_BUCKET
from performance_schema.events_statements_histogram_global
where BUCKET_NUMBER = 12;
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE events_statements_histogram_global NULL const PRIMARY PRIMARY 4 const # 100.00 NULL
############# Explain End #########################################
flush status;
select COUNT_BUCKET
from performance_schema.events_statements_histogram_global
where BUCKET_NUMBER = 12;
COUNT_BUCKET
#
OK: handler_read_key incremented
drop database explain_test_db;
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