mysql structuring comment system, will it take forever?

I'm wondering if I structure my comment system with just one table where I have all my comments and userid will be good?

I want to know if this system will take forever for mysql to get the results if I have lots of comments, and mysql is trying to query only specific userid with the comments associated with it. If anyone have any suggestions, I'd like to hear 开发者_StackOverflow社区it. Thanks!

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It shouldn't be slow. Make sure that you have an index for the user id and the thread id.