I created a sort of voting website with PHP and a MYSQL database. People can vote on id's that are in the database and the amount of likes goes up.
When you click on a button the likes of that specific id goes up by one. This is done through Ajax and sql.
Is it possible to set a limitation of the amount of likes an id can have for each day. For instance each id can update only 10 times each day. And the next day another 10 times.
Yes, you can put condition in ajax code.
Before inserting record in DB for vote first check the total number of vote received for that ID on current day.
If it is equal to 10 then skip the operation or else increase the vote.
You have to put this conditions in this file /10jaar/views/submissions.php
Not a big deal i think so.
Related
I'm trying to learn how to code a website algorithm like Reddit.com where there are thousands of posts that need to be ranked. Their ranking algorithm works like this (you don't have to read it, its more of a general question that I have): http://amix.dk/blog/post/19588
Right now I have posts stored in a database, I record their dates and they each have an upvotes and downvotes field so I'm storing their records. I want to figure out how do you store their rankings? When specific posts have ranking values, but they change with time, how could you store their rankings?
If they aren't stored, do you rank every post every time a user loads the page?
When would you store the posts? Do you run a cron job to automatically give every post a new value every x minutes? Do you store their value? Which is temporary. Maybe, until that post reaches its minimum score and is forgotten?
I did actually read the explanation of the ranking system and if I'm correct they do not care about the current time, but the time of submission of the post. This means the score will change on two points; 1) when the post is submitted, 2) when someone up- or downvotes the post
So you have to (re-)calculate the score when you post something, and when someone up- or downvotes. To recalculate the score isn't that heavy for the server (not at all actually), so just recalculate on vote-changes!
You would most probably use some sort of cache. In addition to post_time, up_votes, and down_votes, you'd have a current_rank, and last_ranked. If last_ranked would be more than say, 20 minutes, you'd rank it again, and if not, display the cached rank.
A different approach would be to rank and save the rank (i.e. current_rank) every time the post is upvoted or downvoted, as well as periodically (every X minutes), then you can just ask the database for the rank, at it would be (pretty) up to date.
I have a website the users can do stuff like leave comments, perform likes, etc..
I want to calcluate a score for each user that is composed from these actions, i.e: Like = 10 points, comment = 20 points etc..
I would like to create a table with users score that will be calculated once a day.
Currently i use a php script and execute, but it takes too long to calculate and then it times-out..
whats the method for perfomring this?
basically what you do is add a record of what the user in your web application, instead of calculating every batch, you can:
save each action along with its own score and then with a simple query that you do every day, update the user's score
keep independent of each action, you can directly add up the score every day user
TIP
as you have planned to update the score every day user can add a cache for a long duration so that the query does not harm performance
How long time does the script take?
If you just want to increase the amount of time the script is allowed to take to execute, you can make use of PHP's set_time_limit() to increase the time.
Start your script by running:
set_time_limit(120); // Script is allowed to execute for 2 minutes if necessary
Say we are a site receiving massive amounts of traffic, Amazon.com size traffic. And say we wanted to display a counter on the home page displaying the total number of sales since December the first and the counter was to refresh via ajax every 10 seconds.
How would we go about doing this?
Would we have a summary database table displaying the total sales and each checkout would +1 to the counter and we would get that number every 10 seconds? Would we COUNT() the entire 'sales' table every 10 seconds?? Is there an external API I can push the stats off to and then do an ajax pull from them?
Hope you can help, Thanks
If your site is ecomm based, in that you are conducting sales, then you MUST have a sales tracking table somewhere. You could simply make the database count part of the page render when a user visits or refreshes your site.
IMO, there is no need to ajax this count as most visitors won't really care.
Also, I would recommend this query be run against a readonly (slave) database if your traffic is truly at amazon levels.
I would put triggers on the tables to manage the counter tables. When inserting a new sale the sum table would get the new value added to the row for the current day. That also gives sales per day historically without actually querying the big table.
Also, it allows for orders to be entered manually for other dates than today and that day get updated statistics.
As for the Ajax part that's just going to be a query into that sum table.
Whatever you do, do not re-COUNT everything every 10 seconds. Why not to have a cronjob, which does the counting of data every 10 seconds? It could take current time-10 seconds and in slave database add the difference to current count ?
Still 10 seconds sound bizarre. Every minute, mm?
I'm building an instant win action for a competition draw. Basically at a given randomly selected minute of an hour, the next user to submit their details should be chosen as the winner.
The problem I'm having is that if MySQL is running multiple connections, then how do I stop two or three winners being drawn by mistake? Can I limit the connections, or maybe get PHP to wait until all current MySQL connections are closed?
have a look at lock tables
http://dev.mysql.com/doc/refman/5.0/en/lock-tables.html
Use the starting value of a field that you're updating as the concurrency check in your WHERE clause when you make the update. That way, only the 1st one to be executed will go through, because after that it will no longer match the WHERE clause. You can tell whose went through using the mysql_affected_rows() function, which will return 1 for the successful update and 0 for any others.
Use a timestamp field "registertime" in the user details table. When inserting the data, use the NOW() function to insert into the registertime field.
When you choose a random minute, convert that to a unix time.
The winner is: SELECT * FROM userTable WHERE registertime > -- the timestamp of your random minute -- ORDER BY registertime LIMIT 1
Keep a small status table somewhere that records the hour of the previous draw. If the new record's insert time is at a different hour, do the check if they're a winner.
If they are, you update the status table with this new "Winners" draw hour, and that'll prevent any more draws being made for the rest of the hour. Though, what happens if, by chance, no one actually "wins" the draw in any particular hour? Do you guarantee a win to the last person who registered, or there just isn't a winner at all?
I have about 10,000 products in the product table. I want to retrieve one of those items and display it in a section of a web page which stays the same for that particular day. Something like "Product of the day".
For example, if today I get product_id 100, then all of the visitors should be viewing this product item for today. Tomorrow it may fetch any random valid primary key, say, 1289 and visitors get 1289 product all day tomorrow.
Any ideas/suggestions?
Thanks for your help.
SELECT id
FROM products
ORDER BY
RAND(UNIX_TIMESTAMP(CURRENT_DATE()))
LIMIT 1
Maybe you can store the id of the item of the day in a table in the database?
How about create a cache file and invalidate it at midnight?
The benefit of this is you don't make unnecessary calls to your DB as you're only checking the timestamp on the cache file - only once per day do you make DB requests to populate a new cache file.
You don't need a CRON job for this:
if(date_of_file(potd_cache_file) != today){
potd_cache_file = generate_from_db();
}
load_file(potd_cache_file);
This will mean only the first visitor of the day to your website will trigger the regeneration, and every subsequent visitor will have a fast loading cache file served to them.
The idea is pretty simple,
Set a table up call ProductOfTheDay with a product ID and a date field
On the product of the day page when a user visits check the date field
If it is todays date then show the product
If it is not then randonly pick a new product and save it to the field.
Its not that complex of an operation.
SELECT id
FROM products
ORDER BY (id + RAND(UNIX_TIMESTAMP(CURRENT_DATE()))) MOD some_reasonable_value
LIMIT 1
You can start random number generators with a seed value.
Make the seed value be the day (21st) + month(10) + year(2009) so today's seed is 2041.
You will get the same random number all day, and tomorrow a different one. This is more how it works in .net. The random function takes a max and min value (this is your min and max ID values) then an optional seed value and returns a number. For the same seed number you get the same random number generated. It's possible if you change the max and min this can affect the number generated. You would have to look up how php works.
total = SELECT COUNT(id) FROM products;
day_product = SELECT id FROM products WHERE id = (UNIX_TIMESTAMP(CURRENT_DATE()) MOD total) LIMIT 1;
See also this question.