'Triggers' Tag

• Limiting table disk quota in MySQL

  March 7, 2011

  Question asked by a student: is there a way to limit a table's quote on disk? Say, limit a table to 2GB, after which it will refuse to grow? Note that the requirement is that rows are never DELETEd. The table must simply refuse to be updated once it reaches a certain size. There is [...]

  posted in MySQL by shlomi

• Thoughts and ideas for Online Schema Change

  October 7, 2010

  Here's a few thoughts on current status and further possibilities for Facebook's Online Schema Change (OSC) tool. I've had these thoughts for months now, pondering over improving oak-online-alter-table but haven't got around to implement them nor even write them down. Better late than never. The tool has some limitations. Some cannot be lifted, some could. [...]

  posted in Development, MySQL by shlomi

• Triggers Use Case Compilation, Part III

  February 2, 2009

  The previous two parts have looked at some solutions offered by triggers. Let's look now at some wishful triggers solutions, which are currently unavailable because of triggers limitations. Triggers Use Case Compilation, Part I Triggers Use Case Compilation, Part II Limitations and wishful features Triggers are slow The overhead of adding triggers is usually an [...]

  posted in MySQL by shlomi

• Triggers Use Case Compilation, Part II

  January 15, 2009

  In Triggers Use Case Compilation, Part I, I've demonstrated some triggers use scenarios. We continue our examples of triggers usage. Counters and aggregations bookkeeping Consider the City table: each city belongs to a certain country. Some questions we may be interested in are: How many cities are there per country? What's the sum of cities [...]

  posted in MySQL by shlomi

• Triggers Use Case Compilation, Part I

  January 5, 2009

  I've run by quite a few triggers lately on production systems. In previous posts, I've written about problems solved with triggers. So here's a compilation of some solutions based on triggers; and some problems which are not (yet?) solvable due to current triggers limitations. Triggers can be used to: Maintain integrity Enhance security Enhance logging [...]

  posted in MySQL by shlomi

• Using triggers to block malicious code: an example

  January 1, 2009

  Web applications face constant exploitation attempts. Those with a user base must keep their users' private data, well... private. While the MySQL security model allows restricting users access to databases, tables and even columns, it has no built in feature for restricting the rows access within the given table. One cannot allow a user to [...]

  posted in MySQL by shlomi

• Using memcached functions for MySQL; an automated alternative to Query Cache

  December 15, 2008

  There's a lot of buzz around memcached. memcached is widely used, and has clients for many programming languages and platforms. TangentOrg have developed a memcached client in the form of MySQL UDFs (User Defined Functions). I wish to discuss the memcached functions for MySQL: if and how they should be used. Disclaimer: I do not [...]

  posted in MySQL by shlomi