June 19, 2013

Post: Using any general purpose computer as a special purpose SIMD computer

May 16, 2011 By 5 Comments

… version as run by the native database interface (MySQL): mysql> select word, md5(word), md5(reverse(word)), count(*) from words2 group by 1… substitution to put the results back together, when necessary. When sorting or grouping are used, a final pass over the final… word AS `word`,md5(word) AS `md5(word)`,md5(reverse(word)) AS `md5(reverse(word))`,COUNT(*) AS `count(*)` FROM words2 AS `words2…

Filed Under: MySQL

Post: InnoDB Full-text Search in MySQL 5.6 (part 1)

February 26, 2013 By 1 Comment

….ibd -rw-rw—-. 1 mysql mysql 98304 Feb 20 16:09 FTS_00000000000000ad_STOPWORDS.ibd -rw-rw—-. 1 mysql mysql 98304 Feb 20 15… constraint violations unless you also do something to provide some sort of sequence value for that column, whether as an auto… in set (0.00 sec) mysql> insert into dir_test_innodb (full_name, details) SELECT reverse(full_name), details FROM dir_test…

Filed Under: Insight for DBAs, Insight for Developers, MySQL Tagged With: , , , , ,

Post: How Percona does a MySQL Performance Audit

November 24, 2008 By 17 Comments

…mysql –user=mysql –pid-file=/var/run/mysqld/mysqld.pid –skip-external-locking –port=3306 –socket=/var/db/mysql/mysql…log. The error log shows all sorts of interesting things. Basically, anything …such as monitoring, alerting, backups, caching, reverse proxies, and high availability solutions, all…

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Post: Descending indexing and loose index scan

May 9, 2006 By 6 Comments

… in reverse order and it will well be. This is how MySQL will optimize indexed ORDER BY col DESC queries for example. Reverse… aready sorted order. This is however something you can workaround by having something like “reverse_date” column and using it for sort. With MySQL… see “reverse_timestamp” field in Wikipedia table structure. Loose index scan – Number of years ago when I just started using MySQL I…

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Comment: Descending indexing and loose index scan

June 21, 2006 By 6 Comments

…” sort but if you need to have reverse sort you need to have something like reverse_timestamp hack. I googled a bit about reverse_timestamp… MySQL before 4.0 WHERE key_part1=const ORDER BY key_part2 DESC simply was not optimized even if you’re sorting by single column. In MySQL 4.0 this problem is fixed and so…

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Post: ORDER BY ... LIMIT Performance Optimization

September 1, 2006 By 100 Comments

…) but MySQL can’t do it at this point. Workaround which can be currently used is separate column which holds reverse values, so you can do ORDER BY col1, col2_reverse instead. Beware of large LIMIT Using index to sort is… is ether extending your indexes so MySQL Optimizer does not have to chose between better sort or better lookup or use FORCE…

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Comment: 7 Reasons why MySQL Quality will never be the same

December 11, 2008 By 15 Comments

… based on anecdotes and bug counts? Will MySQL adapt to this by being less open about… and robust testing methodology.” While true, the reverse is also true. While a robust testing … workloads, and logs containing debugging information. This sort of information is helpful for developers, but …

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Comment: Four ways to optimize paginated displays

September 25, 2008 By 27 Comments

… much faster this way. From what I can tell, the MYSQL optimizer doesn’t take the limit clause into account (or… end of the result set, it’s faste to sort backwards and reverse your limit. e.g. if a query returns 100…

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Comment: Descending indexing and loose index scan

June 20, 2006 By 6 Comments

… an index on (scraped,siteid), but as of MySQL 5.0.21 there is no descending index possible… the descending index? I noticed you mentioned the reverse_timestamp hack in wikipedia, but that is apparently … ‘negative value’ column or something that I could sort ASC, but would effectively be DESC. Thanks…

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