Question

I have a table setup like below.

Table comment_flags
    user_id
    comment_id

I allow users to flag a comment and then give them the option to unflag it, because they may have made a mistake.

The problem is that when they unflag a comment, after I delete the record , the comment_flags table get roughly 30-40bytes of overhead, even after only unflagging 5 comments.

Heres basically whats going on:-

A user flags a comment, so I insert user_id and comment_id into comment_flags table, then the user unflags the comment and I delete from the comment_flags table by the user_id and comment_id.

I am not sure that it’s my SQL thats causing the problem though, I think it’s just the DELETE statement in general.

I could optimise the table after every DELETE statement to clean up the table.

Is this seen as a good idea? How does everyone else deal with this?

My sql is very basic.

INSERT INTO comment_flags VALUE('$user_id', '$comment_id')
DELETE FROM comment_flags WHERE user_id = '$user_id' AND comment_id = '$comment_id'

Answer 1

I could optimise the table after every DELETE statement to clean up the table. Is this seen as a good idea?

For 30-40 bytes? No.

How does everyone else deal with this?

By not bothering. The space should be re-used for any subsequent INSERTs, and this is a good thing.