Comments on: Resolving transaction concurrency issues in a PHP+MySQL multi-user environment http://www.ardamis.com/2008/04/06/resolving-transaction-concurrency-issues-in-a-phpmysql-multi-user-environment/ Ardamis is a tiny web design studio specializing in high-quality, handmade web sites. Tue, 14 Oct 2008 21:09:00 +0000 http://wordpress.org/?v=2.6 By: Tony http://www.ardamis.com/2008/04/06/resolving-transaction-concurrency-issues-in-a-phpmysql-multi-user-environment/#comment-16949 Tony Fri, 26 Sep 2008 11:41:16 +0000 http://www.ardamis.com/2008/04/06/resolving-transaction-concurrency-issues-in-a-phpmysql-multi-user-environment/#comment-16949 Pretty cool solution. To add to that, it works great when process collision is greater than the granularity of the MySql timestamp which is per second. ie, no 2 process will do a read/write within 1 second. To get around this, you can store the time as a bigint which can handle milliseconds. Unless you have some serious hardware, I don't think collision granularity would go smaller than milliseconds. Also instead of re-reading the timestamp before B saves, B should try to UPDATE row WHERE "opened timestamp" = "last modified timestamp". Otherwise the CPU could potentially decide to switch threads on you right after you've done the second read, and do the entire read-write of A in that time. Pretty cool solution. To add to that, it works great when process collision is greater than the granularity of the MySql timestamp which is per second. ie, no 2 process will do a read/write within 1 second.

To get around this, you can store the time as a bigint which can handle milliseconds. Unless you have some serious hardware, I don’t think collision granularity would go smaller than milliseconds.

Also instead of re-reading the timestamp before B saves, B should try to UPDATE row WHERE “opened timestamp” = “last modified timestamp”. Otherwise the CPU could potentially decide to switch threads on you right after you’ve done the second read, and do the entire read-write of A in that time.

]]> By: ardamis http://www.ardamis.com/2008/04/06/resolving-transaction-concurrency-issues-in-a-phpmysql-multi-user-environment/#comment-15859 ardamis Sat, 28 Jun 2008 03:40:51 +0000 http://www.ardamis.com/2008/04/06/resolving-transaction-concurrency-issues-in-a-phpmysql-multi-user-environment/#comment-15859 That's a very interesting PowerPoint presentation, thanks for linking it. And I'm happy to see that we both arrived at the same solution. I hope it serves you well. That’s a very interesting PowerPoint presentation, thanks for linking it. And I’m happy to see that we both arrived at the same solution. I hope it serves you well.

]]> By: jlaguna http://www.ardamis.com/2008/04/06/resolving-transaction-concurrency-issues-in-a-phpmysql-multi-user-environment/#comment-14773 jlaguna Tue, 13 May 2008 06:41:13 +0000 http://www.ardamis.com/2008/04/06/resolving-transaction-concurrency-issues-in-a-phpmysql-multi-user-environment/#comment-14773 Very good explanation, but I did found another source of information including the same idea: http://www.cs.uta.fi/wo/slides/lecture%205.ppt Very good explanation, but I did found another source of information including the same idea:

http://www.cs.uta.fi/wo/slides/lecture%205.ppt

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