Handling problems related to the download performance similar to csdn [welcome to discuss]

Handling csdn-like download performance problems [welcome to discuss] In the csdn download channel, if you have downloaded this attachment, you do not need to deduct points when you download it again next time. I currently have a similar function. my implementation solution is to add a field in my attachment table: download_uids to store all user IDs that have downloaded the attachment. Then, when downloading a file, you must first handle performance issues similar to csdn Download. [welcome to discuss]
In the csdn download channel, if you have downloaded this attachment, you do not need to deduct points when you download the attachment again next time.
I currently have a similar function. my implementation solution is to add a field in my attachment table: download_uids to store all user IDs that have downloaded the attachment. Then, when downloading, use the in_array () function to check whether the user uid exists in the download_uids of the attachment record. if the user uid exists, do not deduct the gold coins, otherwise, array_push will be executed after the gold coins are deducted.

Key point: whether the in_array () operation on the large array (up to 30 K users) has performance problems.
Whether the large array array_push () has performance issues with the large array (up to 30 K users:
------ Solution --------------------
Create a table with 2 fields
Uid save user ID
Did save resource id

Queries whether a user has downloaded a resource.
Select * from tbl_name where uid = $ uid and did = $ did

Query the resources downloaded by the user.
Select * from tbl_name where uid = $ uid

Query which users have downloaded a resource.
Select * from tbl_name where did = $ did