In this blog post, we’ll look at some of the basic housekeeping steps for MySQL indexes. We all know that indexes can be the difference between a high-performance database and a bad/slow/painful query ride. It’s a critical part that needs deserves some housekeeping once in a while. So, what should you check? In no particular order, […]
Read MoreStart of the year and time for the first speaking tour. This time I will take my MySQL Indexing Best Practices presentation to Charlotte on January 14 and Atlanta on January 15. I think this presentation is great for Meetup as it is both providing a lot of very good ready to use practical advice […]
Read MoreThis is the second blog post in the series of blog posts leading up to the talk comparing the optimizer enhancements in MySQL 5.6 and MariaDB 5.5. This blog post is aimed at the optimizer enhancement Multi Range Read (MRR). Its available in both MySQL 5.6 and MariaDB 5.5 Now let’s take a look at […]
Read MoreI have been working with Peter in preparation for the talk comparing the optimizer enhancements in MySQL 5.6 and MariaDB 5.5. We are taking a look at and benchmarking optimizer enhancements one by one. So in the same way this blog post is aimed at a new optimizer enhancement Index Condition Pushdown (ICP). Its available […]
Read MoreWith the growing adoption of Google’s User Statistics Patch**, the need for supporting scripts has become clear. To that end, we’ve created check-unused-keys, a Perl script to provide a nicer interface than directly querying the INFORMATION_SCHEMA database.
Read MoreMySQL does not always make a right decision about indexes usage. Condsider a simple table:
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1 2 3 4 5 6 |
CREATE TABLE `t2` ( `ID` int(11) default NULL, `ID1` int(11) default NULL, `SUBNAME` varchar(32) default NULL, KEY `ID1` (`ID1`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 |
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1 |
SELECT COUNT(*) FROM t2 |
; 250001 (V1)
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1 |
SELECT COUNT(*) FROM t2 WHERE ID1=1 |
; 83036 (V2) (execution time = 110 ms) That is index selectivity by condition (ID1=1) is V2/V1 = 0.3321 or 33.21% It is said (e.g. book “SQL Tuning”) if selectivity over 20% then a full table […]
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