Details
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Bug
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Status: Open (View Workflow)
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Major
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Resolution: Unresolved
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11.4.0, 11.0(EOL), 11.1(EOL), 11.2(EOL), 11.3(EOL)
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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);
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+------+-------------+------------+------+---------------+------+---------+------+-----------+----------+-------+
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| id | select_type | table | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
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+------+-------------+------------+------+---------------+------+---------+------+-----------+----------+-------+
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| 1 | SIMPLE | goodnumber | ALL | NULL | NULL | NULL | NULL | 315011080 | 100.00 | |
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+------+-------------+------------+------+---------------+------+---------+------+-----------+----------+-------+,
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Mysql, explain select count(*) from goodnumber;
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+----+-------------+------------+------------+-------+---------------+---------+---------+------+-----------+----------+-------------+
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| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
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+----+-------------+------------+------------+-------+---------------+---------+---------+------+-----------+----------+-------------+
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| 1 | SIMPLE | goodnumber | NULL | index | NULL | PRIMARY | 42 | NULL | 315054340 | 100.00 | Using index |
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+----+-------------+------------+------------+-------+---------------+---------+---------+------+-----------+----------+-------------+.
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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
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MDEV-5004 Support parallel read transactions on the same snapshot
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- Open
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- Open
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- Closed
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