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Displaying posts with tag: hints (reset)

Working with comma separated list MySQL options
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Over time, some options have crept into the MySQL server which are comma separated lists of options. These include SQL_MODE, optimizer_switch, optimizer_trace and a few other variables.

Optimizer_switch is particularly problematic to work with as it contains many options and is hard to interpret. This is what you usually see when you examine optimizer_switch:




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Further Thoughts on MySQL Upgrades
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I have been upgrading more MySQL database instances recently and have found a few more potential gotchas, which if you are not careful, can potentially be rather nasty. These are not documented explicitly by MySQL, so it may be handy for you to know if you have not come across this type of thing before.

Most of the issues are those related to upgrading MySQL instances which are replicated, either the master servers or the slaves. Some seem specific to the rpm packages I am using (MySQL enterprise or MySQL advanced rpms), though others are not.

Take care upgrading a 5.0 master when you have 5.1 slaves

It is not a good idea to run a …

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MySQL Optimization Hints
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Every programmer loves to optimize, even when we know we shouldn't. To satisfy your cravings MySQL has several keywords that can be placed in your SQL statement to give the database server an explicit optimization instruction.

I should point out that using the hints incorrectly will most likley cause your queries to perform worse, so be sure that it actually makes sense to use them before you go nuts. This means use EXPLAIN and read the documentation on each hint before using.

It's also a good idea to enclose the hints within a SQL comment, for example SELECT /*! …

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