Database efficiency - table per user vs. table of users

Well to answer the specific question: In terms of efficiency of querying, it will always be better to have small tables, hence a table per user is likely to be the most efficient.

However, unless you have a lot of posts and users, this is not likely to matter. Even with millions of rows, you will get good performance with a well-placed index.

I would strongly advise against the table-per-user strategy, because it adds a lot of complexity to your solution. How would you query when you need to find, say, users that have posted on a subject within the year ?

Optimize when you need to. Not because you think/are afraid something will be slow. (And even if you need to optimize, there will be easier options than table-per-user)

The database layout should not change when you add more data to it, so the user data should definitely be in one table.

Also:

• Having multiple tables means that you have to create queries dynamically.

• The cached query plan for one table won't be used for any other of the tables.

• Having a lot of data in one table doesn't affect performance much, but having a lot of tables does.

• If you want to add an index to the table to make queries faster, it's a lot easier to do on a single table.