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drop table if exists t1;
create table t1(n int not null, key(n)) delay_key_write = 1;
select count(distinct n) from t1;
count(distinct n)
100
explain extended select count(distinct n) from t1;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 range NULL n 4 NULL 10 100.00 Using index for group-by
Warnings:
Note 1003 select count(distinct `test`.`t1`.`n`) AS `count(distinct n)` from `test`.`t1`
drop table t1;
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