Database error message for "like": Duplicate entry

[Julius_2000]

Hi all,

looking through the error log I noticed this entry:

Code Select Expand

Database Error: Duplicate entry '30891-msg-33' for key 'smf_user_likes.PRIMARY'
When I try to open the link to that message from the log, I get

Session verification failed. Please try logging out and back in again, and then try again.

It's the first time this occurred. What does it mean? Is this something to be worried about or just minor hiccup?

[Kindred]

Please provide the WHOLE error message...

[Julius_2000]

Dang, stupid me has cleared the log. The message itself is as I posted above. SMF pointed to a likes.php or something among those lines and showed the message link which I couldn't open because of the session verification issue mentioned above. I'll try and comb through the php to see whether I can spot the specific line. Don't know why I didn't post this in the first place. Sorry.

[Doug Heffernan]

Database Error: Duplicate entry '30891-msg-33' for key 'smf_user_likes.PRIMARY'

This error usually happens because there is already an existing value for the column which has been defined as PRIMARY KEY.

[Kindred]

Database Error: Duplicate entry '30891-msg-33' for key 'smf_user_likes.PRIMARY'

This error usually happens because there is already an existing value for the column which has been defined as PRIMARY KEY.

Yup.... but that should not happen in the core product's like system without something else happening to break it.

[Steve]

Still a problem @Julius_2000?

[Julius_2000]

Hi Steve,

it has not occured again but I can't say for sure if it's resolved since I don't know why it happened. Unfortunately I prematurely cleared the log before taking comprehensive notes.

[Steve]

Okay, I'll mark it solved for now but if the issue returns, by all means, mark it as unsolved.

[Julius_2000]

Alright, it happened one more time. This time I'll preserved the log


Off topic: By the way, has the attachment section been reworked? It looks a bit different than I remember.

[Arantor]

I think you have a user double clicking the like button and it trying to insert the same like twice.

I don't think it's a huge concern, but it should be tidied up.

[Julius_2000]

Thanks!

[GL700Wing]

I think you have a user double clicking the like button and it trying to insert the same like twice.

I don't think it's a huge concern, but it should be tidied up.

Double-clicking causes this error because 'insert' statements are used instead of 'ignore' statements (the same issue was reported last year for the 'Thanks for SMF 2.1 mod which I cloned from the native SMF 2.1 'Likes' system).

[Arantor]

Yes, I know, at the time I wrote the above reply I was on mobile and couldn't check if the *other* part of the situation was handled correctly, namely the count of likes on a message.

When I first wrote likes in 2.1 it did, but I also knew it had been massively reworked since I did and wasn't sure if you'd end up with a different problem for just switching insert for ignore where the likes count would get +2 instead of +1, but actually my original implementation and the subsequent restructure both get this correct, forcing a recount rather than just trusting a +1 is appropriate.

[shawnb61]

I cannot reproduce this.

The Like button toggles the state...  If you press it again, it doesn't like it again, it unlikes it...

If you press the like button many times in sequence, even rapidly, it just goes back and forth between liked & not liked. 

[Arantor]

It's a race condition. On your machine the roundtrip is fast enough that you can't beat it.

On this server I can if I really go at it produce 403s, with the error message 'Sorry, but you're not allowed to access the file you requested.' which is I assume the net result of it here, bearing in mind that this is an SMF level error being returned to me with SMF chrome, not something further up or down the stack (e.g rate limiting

(Sorry for the alert spam but I can't like my own posts.)

[shawnb61]

I've tested in multiple online environments.

Can you reproduce the database duplicate key error under discussion?

[GL700Wing]

I cannot reproduce this.

The Like button toggles the state...  If you press it again, it doesn't like it again, it unlikes it...

If you press the like button many times in sequence, even rapidly, it just goes back and forth between liked & not liked. 

I couldn't reproduce it either at the time but @Steve has not reported a repeat of the problem since the code change was made.

[Arantor]

No, but I just proved I can reproduce *an* error in the fashion I outlined?

I personally at this point would change the insert to an insert-ignore in Likes.php and move on with my day because I can see how it could happen and I'm perfectly willing to believe on a less efficient stack than you're working with, that this kind of race condition absolutely could happen.