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Displaying posts with tag: hash indexes (reset)

Advanced MySQL Query Tuning: Webinar followup Q&A
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Thanks to all who attended my “MySQL Query Tuning” webinar on July 24.  If you missed it, you can you can download the slides and also watch the recorded video. Thank you for the excellent questions after the webinar as well. Query tuning is a big topic and, due to the limited time, I had to skip some material, especially some of the monitoring. I would like, however, to answer all the questions I did not get into during the webinar session.

Q: Did you reset the query cache before doing your benchmark on your query? 0.00

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5 ways to make hexadecimal identifiers perform better on MySQL
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One of the most common patterns I see in my consulting work is identifiers that are generated by MD5() or UUID(). Many times this is done in an application framework or something similar — not software the client has written. From the application programmer’s point of view, it’s just an incredibly handy idiom: generate a unique value and use it, you’re done.

Those values tend to appear in session identifiers, but that’s not the only place; I especially notice them in apps that use Java’s Hibernate interfaces, whether session IDs are involved or not. They propagate themselves all around the other tables, where they become secondary indexes and even get combined with other columns to make even bigger keys.

What’s wrong with this? There are two major things that hurt performance in such

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