Customizing SMF > Mod Requests

[PAID] Thread view (AKA tree view)

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Arantor:
Therein lies the problem. How do you store such a thing?

There's two ways. Firstly, each post can deal solely with its immediate parent. Then you're talking about a single extra column in the database. The upside is that it uses very little extra space, the downside is that if you want to do anything other than find the immediate parent or immediate children, you're stuffed. There's no easy way to find children of children, so either you have to fetch every single message from the topic and manually reparse the tree, or you have to recursively query to keep finding children.

There are ways you can maybe clean it up, by limiting parse depth but even so it's still not very clear and only ever going to be efficient under some circumstances. This is the curse of trying to put a square peg in a round hole.

Then you have the other option, maintaining the tree at all times in a separate table but note that you have to store it in a messed up container format to flatten it in such a way that MySQL can handle it (a different symptom of round-hole-square-peg), but then you start using a lot of space, I was finding that the space taken up by this method could sometimes actually exceed the posts themselves.

Sure it was faster, though dealing with moves is slightly more tricky. But the space consumed by it (because you have to essentially replicate the tree in an array then serialize it for MySQL's benefit) outweighed it for me.

But what you're saying, about putting the parent/child into another table, that would actually make little or no difference in the scheme of things, the fact is you're still dealing with a system that would have to recursively process data, or grab it all and process it, whether that's in the main messages table or in a new table - neither has the potential directly to handle a tree structure, it's just not how MySQL is designed, and there's absolutely no escaping that reality.

If it were an option to make use of something like MongoDB or Cassandra, where you can actually store tree objects in a meaningful fashion, maybe it would be feasible, but I assure you, that sort of thing is the way to madness. Managing the same content between multiple systems is a headache and one that you couldn't pay me enough to work on.


Also, note that I did not implement it directly into SMF, I implemented into a heavily, heavily modified SMF. But one where I was able to identify the level of change and I noticed that even on a 100-post thread it was taking up to half a second to process. (And this was on a machine that is also a quad core i7, my laptop)

rbeuker:
So, when will SMF enter the Big Data World? ;) :)

Many thanks for elaborating more on this topic! It got me think about things some more:

- Even though there are the drawbacks and risks that you have described, could a threaded view in your opinion still be something that smaller Forums can use, but bigger Forums (that have a lot of traffic) should avoid? For your reference, my Forum generates about 150,000 to 200,000 pageviews a month (as registered by SMF), so I suppose you'd consider it a low traffic Forum?

- I was wondering: when you were implementing this yourself, where you actually parsing and displaying entire messages in a 'tree'? I am asking, because I don't necessarily need that--just a small 'map' that just shows the message titles and the authors of these messages would already be a big help.

Having such a map would make it possible to very quickly find out of there's an answer to a question, asked by Forum member John on page 12. In a longer thread it could be on page 87! :P

And that just gave me another idea: how about automatically adding a little line to a message after someone has used the 'Quote' button? Something like this:


--- Quote ---Forum member Peter has replied to this on page 87 of this topic. You are on page 12 now and can click 75 times to get there, or click here to immediately go there now!
--- End quote ---

 ;D

Arantor:

--- Quote ---So, when will SMF enter the Big Data World?
--- End quote ---

MongoDB is well known for having issues with so-called Big Data, though more recent versions have improved its reliability, just not particularly its scalability. In any case this isn't a Big Data problem, it's a schema problem and the idea solution is to move to a schemaless structure.


--- Quote ---- I was wondering: when you were implementing this yourself, where you actually parsing and displaying entire messages in a 'tree'?
--- End quote ---

No, that was simply the effort required to actually work out the message ids of said tree.


--- Quote ---And that just gave me another idea: how about automatically adding a little line to a message after someone has used the 'Quote' button? Something like this:
--- End quote ---

Which again raises the problem of the tree.

From given node A, how can you know that node B is a child? Either you log the fact with node B, that node A is the parent, and perform a search when fetching node A (that there are replies), or you log the fact with node A that node B is a child. Great when fetching in that particular case, but painful the other way.

The whole problem is figuring out the map in the first place, because there's no efficient way to store or rebuild part of the tree in isolation, either you store enough to traverse it which keeps it lean, or you store the entire tree which is a massive space consumer.


--- Quote ---so I suppose you'd consider it a low traffic Forum?
--- End quote ---

I was seeing serious problems with even fewer page views.

rbeuker:
Hey hey :)

I'm back! With a new idea: how about storing the information about 'the map' into a separate table? It should probably have at least these columns:

ThreadID
MessageID
ParentMessageID (holds the MessageID of the current message's parent, or NULL if it's the first message at the top level)
MessageLevel (not sure if this would be of any benefit, but it could help drawing the map as it allows for selecting all messages that are on a specific level)

Every time a new message is posted, this table must be updated as well. And the table will have to be populated initially once (after having installed the mod for the first time).

Best regards,

Ronald

Arantor:
Sorry to say it but this is absolutely no different to anything discussed above. The fact it's now in a separate table makes precisely zero difference. Everything you've mentioned has already been referred to for the purposes of trying to make this work.

You still have no way to know where you are in the tree, no way to know what your children are. (The parent is not, and has never been, a problem) It does not change the problem of rebuilding the map, it just changes where the data already needed for it would be stored.

Thing is, this problem is already present in SMF: the board hierarchy has this exact problem, and all the same problems are present there, which is why the whole 'child board of a child board' is never processed fully for performance.


The bottom line: there is absolutely no way you can *efficiently* make a relational table behave in a non-relational way. You can but do it in multiple horrendous fashions (cf what vBulletin and MyBB do, and even they suggest you don't; it's why Kier and co didn't add it to XenForo after they made it in vBulletin before...

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