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Top 5 Wishes for MySQL

 | June 29, 2007 |  Posted In: Insight for DBAs

About a week ago Marten send me email pointing to his article published on Jays Blog (Come on Marten, it is time for you to get your own blog). I should have replied much earlier but only found time to do that now. So here is my list 1. Be Pluggable Unlike many OpenSource projects […]

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Can Innodb Read-Ahead reduce read performance ?

 | June 26, 2007 |  Posted In: Insight for DBAs

I ran into pretty interesting behavior today. We needed to dump and reload large database and we had pretty good IO subsystem so we started number of mysqldump processes in parallel. Unlike in other case when we did load in parallel, dump in parallel did not increase IO rate significantly and we could still see […]

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Does Slow query log logs all slow queries ?

 | June 25, 2007 |  Posted In: Insight for DBAs

One may think one may use MySQL Slow query log to log all slow queries to catch problematic queries or for audit purposes. In fact however not all the queries are logged. I already mentioned mysql slave queries are not logged to slow query log and it looks like I was wrong connecting it just […]

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MySQL 5.1 Command line client improvements

 | June 16, 2007 |  Posted In: Insight for Developers

Just found this little handy feature today:

So now if you press CTRL-C MySQL Command Line Client will not exit but will terminate query being executed. This is great as so many queries assumed CTRL-C would also abort running query in previous MySQL versions and I’ve seen many monstrous queries left running without noticing […]

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Innodb Second Start prevention bug ?

 | June 16, 2007 |  Posted In: Insight for DBAs

I filed the following bug today. Basically it looks like in certain conditions Innodb may be started twice in the parallel on the same data files which can hurt database badly. It is true it does not seems to be 100% repeatable but I’ve seen it multiple times in different environments. I’m not sure if […]

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RAID and Scale Out Discussions

 | June 12, 2007 |  Posted In: Hardware and Storage

Just found this wonderful summary of articles by Jeremy and wanted to give some of my thoughts on the topic. First lets speak about death of the RAID. I think this is far from the case especially if you consider Software RAID here. For many workloads you would like to get RAID just for the […]

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MySQL 4 to MySQL 5 Upgrade performance regressions

 | June 6, 2007 |  Posted In: Insight for DBAs

This week I already had two serious performance regression cases when upgrading from MySQL 4.0 and 4.1 to MySQL 5.0. By serious I mean several times performance difference not just 5-10% you often see for simple queries due to generally fatter code. The problem in both cases was MySQL 5.0 broken group commit bug. First […]

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