Re: Re: Unexplained MySQL Error

[dbwiz]

And for all of you looking for me eating my own words for thinking it could possibly be a problem in the db, and not in my code - keep an eye on this node

I hear you, and I can't wait to see that error in the db.

But in the meantime, allow me to say something abut your code.

• $child could be empty. You don't test if the sub has been passed a value at all.
• I assume that getDb() is returning a database handler, which must either be global, since you don't pass any parameter, or it returns the result of a connection. But if the latter is true, you are not checking for an error, so this sub can fail.
• If getDb does not fail, as I think it doesn't, since you actually got an error from the database, then you are executing a query, again without error checking.
• Your query does not use placeholders. Your "id=$child" can only be correct if (a) id is numeric and (b) $child is not empty and contains a valid number, or (c) id is a text column and $child contains a quoted string . Since you aren't checking if $child has any meningful value, I believe that the reason for your query failure is exactly there.
• If selectrow_arrayref does not fail, it can return either an array reference or undef for an empty set. Therefore, your checking for $res contents is redundant. You can just return $res straight away.

OK. That was only three lines of code, and there were several things that are at least questionable.

Whenever you find the "error in the database," I would be very curious to see it.

Cheers

[jbeninger]

Thanks for the points - as you can see in my "solved" message earlier, I suspect a problem in the DBI package, not the database itself, and even that could be a misinterpretation of the DBI logging system by myself.

To answer your concerns though, $child is checked before getParentCategory is called. It should never be empty, and if it is, it will result in an easily interpreted error. I log the query to the error logs as well as the SQL error so that I can easily locate the source of a problem. Perhaps there should be a die() involved, but that's neither here nor there.

getDb() gets a global database handle that has been tested for success at the beginning of the script. And I can't simply return $res straight away, since I'm returning only the first element - not the reference itself - and if it's undef, then it will fail (undef->[0] causes an error)

Cheers

[jbeninger]

Alright, I'm willing to take the XP loss here by posting this node, but I'd like to know why my rep is so low throughout this node. If my posts are so bad, I'd certainly like to know what's wrong with them so I don't make the same mistakes in the future - it looks bad for me and it wastes your time.

The top node, I can understand. It looks like your standard "I'm getting a weird error and here's what I *think* is going to the database" post by someone who's never used a db before. but even after my clarification and solution, the scores have been abysmal compared to the surrounding ones scorning me for putting up such a spurious node.

Yes, I've read Why did I get downvoted and realize that rep isn't all that important, but it is an indicator of how good your posts are, and it seems that my recent ones have been pretty useless. I'd like that improved, so feel free to lay into me and tell me exactly what you think. I'd prefer not to have this happen again.

Cheers
James Beninger

[Anonymous Monk]

You were downvoted because, after asking for help, you didn't take into account the advice that was given to you.

Instead of trying to act according to what other monks tell you, you are shifting responsibility to something else.

First, you blamed the database, then you said thet the error must be in the DBI. You can't accept the idea that the error can simply be in your code.

It is indeed possible that there is an error in the database of in the DBI, but you can make such a claim only if you have done everything by the book, and only then, when there is nothing else to blame, we can start considering the big guys as guilty.

Tour the Tutorials before you write your next post. :-)