How to make your Like button (I like it)?

Question

PHP

Interested in database storage.
Only one thing comes to mind:
We create a new table and store the id - post and id - user there, we get a many-to-many relationship. Both id's are indexes. And in order not to count how many likes a post has each time, add the `like` field in the table with the post and store the number there and simply display the number on the button.
I doubt that this is not the best option, you will still need to make a selection of all the likes from the 1st user. If there are 10,000 posts and 25,000 users, let's say only 10% of posts like, 10% of users, then the table will be (10.000/100*10)*(25.000/100*10)=2.500.000. I'm afraid that the selection of all likes from the 1st user will take a long time. At this rate, the number of rows can be very large, so how do you store such data? What is the limit in mysql?

Answer 1

SELECT * 
FROM  `forum_search_wordmatch` 
WHERE  `post_id` =127913

Запрос занял 0.0001 сек

The table has 20 million records.
If you are going to store userid, time, postid then 1 record will take a maximum of 40 bytes. In other words: 1Gb ~ 35-40M records.

Answer 2

The limit in MySQL is 255 nines. Those. you cannot store more than 9999 (255 times) records in one table :)

Answer 3

Sampling by PK (or, in your case, parts of it) is fast enough, but first ask yourself: do you need all the user's likes? I doubt that you want to display them on one page, because the user can like a lot and for a long time.
If the number of lines starts to exceed some reasonable number, some sharding algorithms can be applied. In any case, there are no special technical problems.

Answer 4

If you make a like field in the post table. And store there a selection from the table with likes.
Run a selection for the like field via cron, for example, once an hour.