February 2016 - discuss - lists.mariadb.org

[Maria-discuss] intentionally corrupting tables
by Federico Razzoli 02 Feb '16

02 Feb '16

Hi all I am looking for a way to intentionally corrupt a table in a "natural" way. Of course I can open a file with Vim and change random characters, but I would probably obtain a kind of corruption that never occurs in the real world. The purpose is testing recovery procedures. Thanks Federico

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[Maria-discuss] Adding timestamp column to a system
by Peter Mclarty 02 Feb '16

02 Feb '16

Hi All Running Mariadb 10.0.16 and need to add a timestamp column to a table with has around 60m rows Testing on lesser hardware instances suggest around 40 minutes to make this change on the production system. To reduce the down time I was planning to alter the slave and role swap the slave to become the master I have added the column to a test slave and notice it alway populates as Unix_epoch 0 ie no current timestamp date | timestamp 2016-01-29 | 0000-00-00 00:00:00 This sounds about right, but to confirm it's not a bug. Other than the timestamp value not being correct up to that time of making any changes, which is acceptable for why it is being added, like the role swap, is there any things to be concerned about if I follow that as an approach? The role swap was needing to be done soon anyway so that in itself isn't a stumpling block I know Percona has their tools that allow online schema changes, I have never used it in anger to achieve this sort of change. Would I be better off using that. Cheers -- *Peter McLarty* * DBA* -- Compare The Market is a brand and trading name of Compare The Market (Pty) Ltd (CTM). This email is for the intended addressee and is confidential and subject to copyright. If you are not the intended addressee, confidentiality has not been waived and any use, interference with, or disclosure of this email is unauthorised. If you are not the intended addressee please immediately notify CTM and then delete the email. CTM does not warrant that this email is error or virus free.

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[Maria-discuss] New Question: Phenomenon of read-only queries performance
by AskMonty KB 02 Feb '16

02 Feb '16

Hello, A new question has been asked in "MariaDB Community" by knizhnik_g. Please answer it at http://mariadb.com/kb/en/phenomenon-of-read-only-queries-performance/ as the person asking the question may not be subscribed to the mailing list. -------------------------------- We are evaluating Galera cluster with MariaDB and find out interesting phenomenon which we can not explain. We are using standard sysbench compex-OLAP, 10 million records. Performance of read-only queries is about 3k TPS and is quite stable. But then we run for a while read-write version and after it once again read-only version, then in this case performance starts to grow from 4k till 10k TPS. 10K TPS is reached after about 30 seconds of running benchmark and stays at this level. But if we stop benchmark and restart it, then once again speed falls down to 3k TPS. Data is located in temporary file system, so disk is not involved at all. We used recommended configuration settings for MariaDB and Galera. Also the same behavior is observed with standalone mysql without Galera: performance of read-only queries varies from 3k to 6k TPS (but high values are smaller than with Galera, although no load balancing was performed). Is there any explanation of such behavior and where we can look trying to understand the reason? Why performance of standalone mysql can be slower than on Galera cluster? How we can tune it? -------------------------------- To view or answer this question please visit: http://mariadb.com/kb/en/phenomenon-of-read-only-queries-performance/

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[Maria-discuss] Performace issue with insert
by walter harms 01 Feb '16

01 Feb '16

Hello list, i have a strange problem with inserts. The tables is large (time series data) and has a lot of partitions, engine is IMMODB. We have notice that the write performance decreases with time, start of the month good, end of the month bad. The same behavier is the lasted version of mariadb. But when i replace mariadb with mysql the problems vanishes (so its not a hardware issue). I suspect that it is a caching problem but a comparison of the configs did not give a hint. Anyone an idea what may cause the effect ? re, wh

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