Details
-
Bug
-
Status: Closed (View Workflow)
-
Major
-
Resolution: Fixed
-
N/A
-
Related to performance
-
Q1/2026 Server Development
Description
There is an approx 1.6% to 3% performance regression for INSERTs when using the default hashing algorithm for partitioning after the MDEV-9826 implementation:
CREATE TABLE t (c1 INT NOT NULL, c2 INT, c3 INT, PRIMARY KEY (c1)) ENGINE=InnoDB PARTITION BY KEY(c1) PARTITIONS 16; |
SHOW CREATE TABLE t; |
INSERT INTO t (c1, c2, c3) SELECT seq, seq, seq FROM seq_1_to_200000000; |
Yields on the feature tree (bb-main-mdev-9826-v4 at 775ad15a80bf26ce5d29b237110477547631289b):
|
bb-main-mdev-9826-v4 CS 12.3.0 775ad15a80bf26ce5d29b237110477547631289b (Optimized, Clang 21.1.3-20250923) Build 20/12/2025 |
12.3.0-opt>INSERT INTO t (c1, c2, c3) SELECT seq, seq, seq FROM seq_1_to_200000000;
|
Query OK, 200000000 rows affected (6 min 23.711 sec)
|
Records: 200000000 Duplicates: 0 Warnings: 0
|
Versus the same tree --1 commit (i.e. bb-main-mdev-9826-v4 at e85bc659188be021897e8578aec42becfbb58c27}:
|
bb-main-mdev-9826-v4 unpatched CS 12.3.0 e85bc659188be021897e8578aec42becfbb58c27 (Optimized, Clang 21.1.3-20250923) Build 20/12/2025 |
12.3.0-opt>INSERT INTO t (c1, c2, c3) SELECT seq, seq, seq FROM seq_1_to_200000000;
|
Query OK, 200000000 rows affected (6 min 12.841 sec)
|
Records: 200000000 Duplicates: 0 Warnings: 0
|
Which is a ((383.711 / 372.841) - 1) * 100 = 2.9154% performance regression. The number varies but often land around the 2.x mark.
The regression is consistently reproducible, including with MyISAM instead of InnoDB.
Attachments
Issue Links
- is blocked by
-
-
- Closed
-
- is caused by
-
MDEV-9826 better hash algorithms for PARTITION BY KEY
-
- Closed
-
- split to
-
MDEV-38682 Further hasher performance improvement following MDEV-9826
-
- Open
-