问题
I need a way to modify a value in a table after a certain amount of time has passed. My current method is as follow:
- insert end time for wait period in table
- when a user loads a page requesting the value to be changed, check to see if current >= end time
- if it is, change the value and remove the end time field, if it isn't, do nothing
This is going to be a major feature on the site, and so efficiency is the key; with that in mind, you can probably see the problem with how I'm doing it. That same chunk of code is going to be called every time someone access a page that needs the information.
Any suggestions for improvements or better methods would be greatly appreciated, preferably in php or perl.
In response to cron job answers: Thanks, and I'd like to do something like that if possible, but hosts limits are the problem. Since this is a major part of the app, it can't be limited.
回答1:
why not use a cron to update this information behind the scenes? that way you offload the checks on each page hit, and can actually schedule the timing to meet your app's requirements.
回答2:
Your solution sounds very logical, since you don't have access to cron. Another way could be storing the value in a file, and the next time the page is loaded check when it was last modified (filemtime("checkfile.txt")), and decide if it needs modifying again. You should test performance for both methods.
回答3:
Can you use a cron job to check each field in the database periodically and update that way?
A big part of this is how frequently the updates are required. A lot of shared hosts limit the frequency of cron checks, for example no more than every 15 minutes, which could affect the application.
回答4:
You could use a trigger of some sort on each page load. I really have no idea how that would affect performance but maybe somebody else can shed some light.
回答5:
If performance really starts to be an issue, (which means a lot more than you probably realize) you could use memchached to store the info...
来源：https://stackoverflow.com/questions/122954/timed-events-with-php-mysql