March 2025 - discuss - lists.mariadb.org

[Maria-discuss] explain for insert/update/delete
by MARK CALLAGHAN 08 Jul '25

08 Jul '25

Does MariaDB have any plans to support explain for insert/update/delete/replace/CTAS? There have been feature requests open for a very long time on official MySQL without any progress. I have had a few problems in production from 'bad' delete statements that had a very different plan than the select statement with the same where clause. The only way to check for a bad plan today is to use SHOW INNODB STATUS to determine whether the statement locks all rows in a table. http://bugs.mysql.com/bug.php?id=14745 http://bugs.mysql.com/bug.php?id=35355 -- Mark Callaghan mdcallag(a)gmail.com

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[Maria-discuss] Galera 23.2.7 mariadb 5.5.33a msvc 1600 binaries available
by Yann Nayn 21 May '25

21 May '25

Binaries have been uploaded for both x86 and amd64 platforms. due to github file size limitations , the directories have been uploaded unarchived. for Win33 binaries , please checkout https://github.com/YannNayn/galera-mariadb-win32.git and for Win64(amd64) binaries (being uploaded/pushed): https://github.com/YannNayn/galera-mariadb-win64.git they are not recommended for a production environment. in the my.cnf file: _________ wsrep_provider=galera_smm.dll wsrep_sst_method=msqldump # percona xtrabackup will be tested soon _________ libevent and openssl(the provided binaries use respectively 2.1.3-alpha and 1.1.0-dev versions ) will be added next on github some limitations are stated on openssl website copied here for convenience: ____________ from http://www.openssl.org/ ____________ This software package uses strong cryptography, so even if it is created, maintained and distributed from liberal countries in Europe (where it is legal to do this), it falls under certain export/import and/or use restrictions in some other parts of the world. PLEASE REMEMBER THAT EXPORT/IMPORT AND/OR USE OF STRONG CRYPTOGRAPHY SOFTWARE, PROVIDING CRYPTOGRAPHY HOOKS OR EVEN JUST COMMUNICATING TECHNICAL DETAILS ABOUT CRYPTOGRAPHY SOFTWARE IS ILLEGAL IN SOME PARTS OF THE WORLD. SO, WHEN YOU IMPORT THIS PACKAGE TO YOUR COUNTRY, RE-DISTRIBUTE IT FROM THERE OR EVEN JUST EMAIL TECHNICAL SUGGESTIONS OR EVEN SOURCE PATCHES TO THE AUTHOR OR OTHER PEOPLE YOU ARE STRONGLY ADVISED TO PAY CLOSE ATTENTION TO ANY EXPORT/IMPORT AND/OR USE LAWS WHICH APPLY TO YOU. THE AUTHORS OF OPENSSL ARE NOT LIABLE FOR ANY VIOLATIONS YOU MAKE HERE. SO BE CAREFUL, IT IS YOUR RESPONSIBILITY. ________________________________________________ msvc 1600 redistributables SP1 need to be installed/available on the target machine: vcredist_x86.exe : http://www.microsoft.com/en-us/download/details.aspx?id=8328 vcredist_x64.exe : http://www.microsoft.com/en-us/download/details.aspx?id=13523 MSys binaries are provided and msqld.bat should then be used instead of mysqld.exe (e.g. mysld.bat --console --wsrep_cluster_address=gcomm:// ) in order to have a working sh shell(cygwin has been proved to do it as well) Please note that oqgraph is disabled (boost trunk is used , that is 1.55) Comments and suggestions are welcome.

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10.11.8 writing all binary logs in row format (even though format is MIXED)
by mariadb＠Biblestuph.com 14 May '25

14 May '25

Doing a little fishing here ... Does someone know of a reason why a downstream replica would--seemingly spontaneously--start writing ALL of its binary log entries in ROW format, even though binlog_format is MIXED? This replica has been running for quite some time, though admittedly I had to restore it from a backup about 3 weeks ago as the result of a server crash. But it had been writing data fine over those three weeks (and prior); starting on March 2nd it started writing all of its entries in ROW format. I didn't notice until it filled the disk this morning. I can't think of anything that may have changed at that time. Normally a few entries will get written as ROW but most are definitely MIXED in normal operation. I stopped/restarted it this morning and it's writing in MIXED again, as expected. I also checked the upstream primary, it is _not_ writing its records as ROW. I.E., my replica is (apparently) not getting them that way from upstream. Both are 10.11.8. Any ideas? TIA, Dan

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Re: Fixing typos
by Lakhin Vasilii 29 Apr '25

29 Apr '25

Forgot to attach the patch I mentioned.

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Busy_time rate is a million times higher from 11.4.4 to 11.4.5
by mdbml.myself854＠passmail.net 14 Apr '25

14 Apr '25

Good day When I start a 11.4.4 image and I watch USER_STATISTICS.BUSY_TIME refreshing it every second or so, it increases with about 0.0002 at a time (for a user that's not really doing anything). But when I do the same in a 11.4.5 image it goes up by about 200 at a time (while the user is still not doing anything). I think that's wrong because it's supposed to be "number of seconds of activity". I couldn't find anything about it in the release notes https://mariadb.com/kb/en/mariadb-11-4-5-release-notes/ . Any ideas? I also see this in production and it quite messes up our metrics 😅 Thanks you

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increasing InnoDB history length and stalls on MariaDB 11.4
by kazuhiko＠nexedi.com 10 Apr '25

10 Apr '25

Hello, Our application has a sustained rate of DML queries in parallel with DQL. We can achieve good performance using innodb-locks-unsafe-for-binlog on MariaDB 10.4, with careful consideration of its 'unsafeness'. But innodb-locks-unsafe-for-binlog is removed in MariaDB 10.5 or later and our application runs much slower without it because of gap locking. https://mariadb.com/docs/server/ref/mdb/cli/mariadbd/innodb-locks-unsafe-fo… To achieve a good performance as before, we now use READ COMMITTED transaction isolation for DML and use REPEATABLE READ isolation for DQL on MariaDB 11.4. This way guarantees the consistency for our application. Our database contains totally 13.7G rows and uses 4.5TB storage. Here is the configuration : innodb_buffer_pool_size = 17179869184 (16GB) innodb_buffer_pool_instances = 16 (no meaning in 11.4) innodb_log_file_size = 134217728 (128MB) innodb_flush_method = O_DIRECT Please see the attached graphs drawing 'InnoDB history length (right axis)' and 'free redo log in % (left axis)' (i.e. 100 - Redo Log Occupancy) while running our reference workload. https://mariadb.com/kb/en/innodb-redo-log/#determining-the-redo-log-occupan… These tests are done with the same workload, but only MariaDB version and/or configuration is different. (Please disregard the 'warehouse history length' and 'activities history length' series in those plots, they are not relevant to the current issue.) On MariaDB 10.4, the performance and the behaviour between 'using innodb-locks-unsafe-for-binlog' and 'using READ COMMITTED and REPEATABLE READ' are similar. But on MariaDB 11.4, I found two serious issues. Issue 1: InnoDB history length keeps growing while running lots of DML and DQL queries in parallel. InnoDB history length is stable around 5k on 10.4, but it keeps growing on 11.4 up to 100k until the end. In our experience, increases in history list length are roughly correlated with poor query performance (causing queries to "step over tombstones" ?), and we do our best to avoid having long-running transactions in order to allow older snapshots to be freed ASAP. We are satisfied with the status on 10.4, where history list is constant. What is the reason behind such increases on 11.4 and is there any configuration to avoid such ? Issue 2: MariaDB stalls when free redo log is too small. When MariaDB stalls, even a quite simple query takes too long. (table definition) CREATE TABLE `catalog` ( `uid` bigint(20) unsigned NOT NULL, `path` varchar(255) NOT NULL DEFAULT '', ... PRIMARY KEY (`uid`), KEY `Path` (`path`), ... ) (from pt-query-digest output) # Attribute pct total min max avg 95% stddev median # ============ === ======= ======= ======= ======= ======= ======= ======= # Count 2 91 # Exec time 2 716s 1s 17s 8s 15s 5s 7s # Lock time 0 22ms 156us 491us 238us 366us 70us 204us # Rows sent 0 663 3 10 7.29 8.91 1.09 6.98 # Rows examine 0 663 3 10 7.29 8.91 1.09 6.98 # Rows affecte 0 0 0 0 0 0 0 0 # Bytes sent 0 52.10k 330 749 586.24 685.39 68.46 563.87 # Query size 0 470.83k 3.56k 5.26k 5.17k 5.20k 225.56 5.20k SELECT uid, path FROM catalog WHERE path in ('...', /*... omitted 80 items ...*/)\G (here, these SELECT are issued in READ COMMITTED isolation level) Our understanding is that the stalls are caused by the undo log cleanup job, and/or the innodb buffer pool writeback job. Increasing the undo log size a lot seems to reduce the frequency of those stalls. For our reference workload here, we still have stalls with 1GB log file but we don't have stalls with 2GB or more log file. If we need 'big enough' log file size to avoid stalls, will the ideal size be proportional to the amount of data or proportional to the buffer pool size ? We have never had such stall on MariaDB 10.4 even with small 128MB log file. How this difference happen and is there any configuration to improve the behaviour ? Thanks in advance ! Best regards, Kazuhiko SHIOZAKI

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Adding an index to a large table
by edi mari 04 Apr '25

04 Apr '25

Hi, I have a 200GB table with a foreign key constraint, and I need to drop an existing index and add a non-unique index to it. What is the best approach to do this with minimal impact on users? Thanks Edi

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InnoDB buffer pool usage drops regularly since 10.11.10 / 11.4.4
by William David Edwards 02 Apr '25

02 Apr '25

Hi, We see an odd pattern where InnoDB buffer pool usage drops regularly. Attached are two screenshots of memory usage on an 11.4.4 node: one at 20:15 with an InnoDB buffer pool of 47,5 GiB, and 5 minutes later with a 3,69 GiB one. The times at which this occurs are -seemingly- random. Other internal memory structures are stable. On at least one node with this issue, the InnoDB buffer pool is smaller (48 GiB) than the sum of data + indexes (87,57 GiB). As far as I can see (graphing history is limited), this has started occurring after upgrading from MariaDB 10.11.9 to 10.11.10 and from 11.4.3 to 11.4.4 respectively. At first sight, in the pre-release notes for 10.11.11 and 11.4.5, I don't see any related issues. To make absolutely sure this is related to the upgrade, we will be downgrading a troubled node tonight, to see if it fixes anything. I will report back. In userland, these drops cause a domino effect: no cache -> more I/O -> slower queries -> nuisance in application. Has anyone else seen this pattern, possibly after upgrading to the aforementioned versions? Although 1) neither of these versions are bleeding edge and 2) I haven't seen any such reports, asking is worth a shot as this started occurring on several machines after upgrading with no configuration nor (obvious) usage changes. With kind regards, William David Edwards

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is blocked because of many connection
by Marc 31 Mar '25

31 Mar '25

I am constantly getting abuse from azure, amazon, digital ocean cloud. With previous mysql versions I never got this message. I assume you have set this to a default. I don't want to have this limit on ip but on ip+database, how can I change this?

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Re: Troubleshooting major performance issue.
by pslawek83 30 Mar '25

30 Mar '25

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