Details
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New Feature
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Status: Open (View Workflow)
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Major
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Resolution: Unresolved
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None
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Q4/2025 Server Development
Description
Test case from https://bugs.launchpad.net/percona-server/+bug/1348295 gives the same result (uneven data disctribution) on recent MariaDB 10.1.13:
[openxs@fc23 maria10.1]$ bin/mysql -uroot test
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Reading table information for completion of table and column names
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You can turn off this feature to get a quicker startup with -A
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Welcome to the MariaDB monitor. Commands end with ; or \g.
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Your MariaDB connection id is 3
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Server version: 10.1.13-MariaDB Source distribution
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Copyright (c) 2000, 2016, Oracle, MariaDB Corporation Ab and others.
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Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
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MariaDB [test]> drop table t1;
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Query OK, 0 rows affected (0.18 sec)
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MariaDB [test]> create table t1(c1 int, c2 date) partition by key(c2) partitions 8;
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Query OK, 0 rows affected (1.92 sec)
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MariaDB [test]> insert into t1 values (1, '2014-04-22');
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Query OK, 1 row affected (0.04 sec)
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MariaDB [test]> insert into t1 values (1, '2014-04-23');
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Query OK, 1 row affected (0.04 sec)
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MariaDB [test]> insert into t1 values (1, '2014-04-24');
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Query OK, 1 row affected (0.04 sec)
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MariaDB [test]> insert into t1 values (1, '2014-04-25');
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Query OK, 1 row affected (0.04 sec)
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MariaDB [test]> insert into t1 values (1, '2014-04-26');
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Query OK, 1 row affected (0.15 sec)
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MariaDB [test]> insert into t1 values (1, '2014-04-27');
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Query OK, 1 row affected (0.05 sec)
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MariaDB [test]> insert into t1 values (1, '2014-04-28');
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Query OK, 1 row affected (0.04 sec)
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MariaDB [test]> insert into t1 values (1, '2014-04-29');
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Query OK, 1 row affected (0.12 sec)
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MariaDB [test]> insert into t1 values (1, '2014-04-30');
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Query OK, 1 row affected (0.07 sec)
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MariaDB [test]> select partition_name, table_rows from information_schema.partitions where table_name='t1';
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+----------------+------------+
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| partition_name | table_rows |
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+----------------+------------+
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| p0 | 3 |
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| p1 | 0 |
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| p2 | 0 |
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| p3 | 0 |
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| p4 | 2 |
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| p5 | 0 |
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| p6 | 4 |
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| p7 | 0 |
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+----------------+------------+
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8 rows in set (0.00 sec)
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MariaDB [test]>
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No wonder, as this is upstream bug known also as:
https://bugs.mysql.com/bug.php?id=72428
https://bugs.mysql.com/bug.php?id=65112
Percona set the bug to "Won't fix" and Oracle seems to postpone fixing as the fix requires changing of hash algorithm and may result in backward compatibility issues.
I wonder if mariaDB can implement new hashing algorithm for KEY partitioning (maybe under some new "name"/partition type) in 10.1 or 10.2, one that distributes data in a more even/expected way?
Attachments
Issue Links
- is duplicated by
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MDEV-22831 PARTITION BY KEY ALGORITHM={crc32|murmur|...}
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- Stalled
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- relates to
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MDEV-32016 change the hash used for hash unique
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- Open
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