Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>What kind of conflicts are you afraid of in solution 2? I assume you refer to the possibility that you are computing a mark and in the meanwhile a new mark is provided and you start the same computation again where the second computation is stored before the first. In other words, you are not having the latest average.</p> <p>Before giving an answer, I think you should just get your code working in the easiest way. Only when you are running into problems I would consider optimizations. You will need quite a number of marks and visitors (assuming web interface) before you will really benefit from any optimization. Optimize it later is my advice.</p> <p>To the answer, I would consider 3 options. I do not know Play2 so I keep my answer generic.</p> <p>1) Don't care: The change this happens is rather limited and only a problem with very high traffic. As you are only computing a temporary value (until new marks are there) I'd ignore the possibility. Next time somebody provides a mark, your stats will be correct. 1a) You could re-calculate the averages every night to make sure they are correct for the next day.</p> <p>2) Ensure the calculations are synchronized. In other words, make sure there are never 2 calculations started at the same time. There are multiple options for that and as I do not know Play2 I'd refer from giving more info.</p> <p>3) This is the nicest way to do. As you are expecting high traffic, you want to secure you can serve your customers. The last thing you want is e.g. spending 50% of your CPU power to doing calculations. One option is to make a seperate process running in the background checking once in a while the marks table. Once it detects a new mark, it will compute the average. As you have only 1 process, you limit the CPU time it takes and the load on the database. During high load, you might be a bit behing in your calculations, but this will speed up once load is lower.</p> <p>If you are really going for heavy traffic, go for option 3). Based on your question, I'd advice to take option 1) for your product, investigate option 2 to learn more about e.g. semaphores and consider option 3) as a learning exercise.</p> <p>Good luck.</p>
    singulars
    1. This table or related slice is empty.
    1. POSave an average vs Compute it at every request
      singulars
      1. PTQuestion
    1. PTAnswer
    1. This table or related slice is empty.
    1. USVincent Nikkelen
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POSave an average vs Compute it at every request
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COThis is what I call a complete answer, thanks :) ! You're right, I think I'm going to opt for your first solution, the idea of re-calculating the average every night is very good. If I have problems in the future I'll investigate for solution 3.
      singulars
      1. PO
      1. USc4k
    2. COGlad I could help. Should have added that option 3 is ideal for executing actions that might fail and need to be repeated. I use it e.g. for sending email; if the SMTP server is down then I do not need to care about it in my code. I have an other process (started with cron) that fetches the data and tries again periodically. It keeps your code clean (main code only puts data in the dd) and robust (using it as well for push messages on Android/iPhone)
      singulars
      1. PO
      1. USVincent Nikkelen
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload