Join 7000 others and follow Sean Hull on twitter @hullsean. MySQL’s optimizer can do a lot of things, but subqueries are not always handled well. Take a look at the IN subquery below. If you see the DEPENDENT SUBQUERY in your explain plan, you may want to take a second look. This will run slow [...]
Jun
26
2013
Jun
19
2013
Join 6100 others and follow Sean Hull on twitter @hullsean. Lots and lots of web applications need to page through information. From customer records, to the albums in your itunes collection. So as web developers and architects, it’s important that we do all this efficiently. Start by looking at how you’re fetching information from your [...]
Jun
17
2013
Join 6500 others and follow Sean Hull on twitter @hullsean. I just received my copy of the 5th Edition of Paul DuBois’ MySQL tomb. Weighing in at 1153 pages, it’s a solid text, with a very thorough introduction to the topic of administering MySQL databases. Buy the book here: MySQL 5th Edition by Paul Dubois [...]
Jun
13
2013
Join 6100 others and follow Sean Hull on twitter @hullsean. There are two ways to speedup UNIONs in a MySQL database. First use UNION ALL if at all possible, and second try to push down your conditions. [mytweetlinks] 1. UNION ALL is much faster than UNION How does a UNION work? Imagine you have two [...]
Jun
11
2013
Join 6100 others and follow Sean Hull on twitter @hullsean. The Foundation of Speed All servers use disk to store files. Operating system libraries, webserver & application code, and most importantly databases all use disk constantly. So disk speed is crucial to server speed. [mytweetlinks] [quote] Disk speed is crucial for MySQL databases. It has [...]
Jun
05
2013
Read the original article at Five More Things Deadly to Scalability
Join 6000 others and follow Sean Hull on twitter @hullsean. 1. Slow Disk I/O – RAID 5 – Multi-tenant EBS Disk is the grounding of all your servers, and the base of their performance. True with larger and larger main memory, much is available in cache, a server still needs to constantly read from disk [...]
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May
29
2013
Read the original article at The Needle in Big Data Noise
Join 5500 others and follow Sean Hull on twitter @hullsean. Also take a look at: I hacked Disqus Digests to discover new blogs Who the heck is Bayes Thomas Bayes was a scientist & thinker, Fellow of the Royal Society, and back in 1763 author of “An Essay toward Solving a Problem in the Doctrine [...]
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Apr
30
2013
We’ve told you all about MySQL mult-master replication’s limitations. If you write to two masters it is bound to fail for myriad reasons. Now what? Do what the pros do that’s what. A. Don’t write to both masters Using multi-master replication works great as long as you do so in active-passive mode. Never write to [...]
Apr
18
2013
Read the original article at Transaction isolation breaks when writing two masters
Continuing our discussion of multi-master replication, we hit on five more reasons why writing to two masters aka active-active replication is very dangerous. Click through to the end for multi-master solutions that work with MySQL. Reason 6 – You lose transaction isolation This may sound like a theoretical point to some. But hopefully we can [...]
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Apr
16
2013
Read the original article at 10 reaons active-active is hard and how to solve it
Multi-master replication provides redundant copies of your most important business assets. What’s more it allows applications to scale out, which is perfect for cloud hosting solutions like Amazon Web Services. But when you decide you need to scale your write capacity, you may be considering active-active setup. This is dangerous, messy and prone to failure. [...]
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