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create table t1(c1 int not null, c2 double not null, c3 char(255) not null) engine=archive charset=latin1;
insert t1 select seq, seq+0.7, concat('row with c1 = ', seq) from seq_1_to_10;
explain partitions select c1,c3 from t1 order by c2;
id select_type table partitions type possible_keys key key_len ref rows Extra
1 SIMPLE t1 NULL ALL NULL NULL NULL NULL 10 Using filesort
set max_length_for_sort_data = 4;
explain partitions select c1,c3 from t1 order by c2;
id select_type table partitions type possible_keys key key_len ref rows Extra
1 SIMPLE t1 NULL ALL NULL NULL NULL NULL 10 Using temporary; Using filesort
flush status;
select c1,c3 from t1 order by c2;
c1 c3
1 row with c1 = 1
2 row with c1 = 2
3 row with c1 = 3
4 row with c1 = 4
5 row with c1 = 5
6 row with c1 = 6
7 row with c1 = 7
8 row with c1 = 8
9 row with c1 = 9
10 row with c1 = 10
set max_length_for_sort_data = default;
show status where variable_name like '%tmp%' and value != 0;
Variable_name Value
Created_tmp_tables 1
Handler_tmp_write 10
Rows_tmp_read 20
alter table t1 partition by hash (c1) partitions 3;
explain partitions select c1,c3 from t1 order by c2;
id select_type table partitions type possible_keys key key_len ref rows Extra
1 SIMPLE t1 p0,p1,p2 ALL NULL NULL NULL NULL 10 Using filesort
set max_length_for_sort_data = 4;
explain partitions select c1,c3 from t1 order by c2;
id select_type table partitions type possible_keys key key_len ref rows Extra
1 SIMPLE t1 p0,p1,p2 ALL NULL NULL NULL NULL 10 Using temporary; Using filesort
flush status;
select c1,c3 from t1 order by c2;
c1 c3
1 row with c1 = 1
2 row with c1 = 2
3 row with c1 = 3
4 row with c1 = 4
5 row with c1 = 5
6 row with c1 = 6
7 row with c1 = 7
8 row with c1 = 8
9 row with c1 = 9
10 row with c1 = 10
set max_length_for_sort_data = default;
show status where variable_name like '%tmp%' and value != 0;
Variable_name Value
Created_tmp_tables 1
Handler_tmp_write 10
Rows_tmp_read 20
drop table t1;
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