Details
-
Bug
-
Status: Open (View Workflow)
-
Major
-
Resolution: Unresolved
-
11.1(EOL), 11.2, 11.4.0, 11.0(EOL), 11.3(EOL)
-
Linux
Description
I compared the "explain" output of two select count(*) from table, identical tables, one mariadb and the other "mysql 8.3", and they are different. The tables have one single field, varchar(10) and it's the primary key. I need to understand the difference:
Mariadb:
explain extended select count(*) from goodnumber force index(primary);
|
 |
+------+-------------+------------+------+---------------+------+---------+------+-----------+----------+-------+
|
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
|
+------+-------------+------------+------+---------------+------+---------+------+-----------+----------+-------+
|
| 1 | SIMPLE | goodnumber | ALL | NULL | NULL | NULL | NULL | 315011080 | 100.00 | |
|
+------+-------------+------------+------+---------------+------+---------+------+-----------+----------+-------+,
|
Mysql, explain select count(*) from goodnumber;
|
+----+-------------+------------+------------+-------+---------------+---------+---------+------+-----------+----------+-------------+
|
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
|
+----+-------------+------------+------------+-------+---------------+---------+---------+------+-----------+----------+-------------+
|
| 1 | SIMPLE | goodnumber | NULL | index | NULL | PRIMARY | 42 | NULL | 315054340 | 100.00 | Using index |
|
+----+-------------+------------+------------+-------+---------------+---------+---------+------+-----------+----------+-------------+.
|
The fastest result is the latter, like 10 times. Does it mean that the commercial version of MySQL by Oracle has a better optimizer and it counts the records on a table about 10 times faster?
Attachments
Issue Links
- relates to
-
MDEV-5004 Support parallel read transactions on the same snapshot
-
- Open
-
-
-
- Open
-
-
-
- Closed
-