Most efficient database design for a blog (posts and comments)

Question

What would be the best way of designing a database to store blog posts and comments? I am currently thinking one table for posts, and another for comments, each with a post ID.<

Answer 1

Okay, let's see.

trawling through a large table of comments to find those for the relevant post would be expensive

Why do you think it'd be expensive? Because you possibly believe that a linear search will be done every time taking O(n) time. For a billion comments, a billion iterations will be done.

Now suppose a binary search tree is constructed for comment_ID. To look up any comment, you need log(n) time [base 2]. So for even 1 billion comments, only around 32 iterations will be needed.

Now consider a slightly modified BST, where each node contains k elements instead of 1 (in a list) and has k+1 children nodes. The same properties of BST are followed in this data structure as well. What we've got here is called a B-tree. More reading : GeeksForGeeks - B Tree Introduction

For a B-Tree, the lookup time is log(n) [base k]. Hence, if k=10, for 1 billion entries, only 9 iterations will be needed.

All databases save indexes for primary keys in B-Trees. Hence, the stated task would not be expensive, and you should go ahead and design the database the way it seemed obvious.

PS: You can build an index on any column of the table. By default primary key indexes are already stored. But be careful, do not make unnecessary indexes as they take up disk space.