DBX - SQL queried XML DBMS in PHP

Anon

Hi, and though this might seem like a propoganda, I really think people might be interested in this:

A friend of mine and I have come up with a PHP script that we call DBX, and it is a small scale Database engine.

What's cool about it is that it's a small(<20k) DBMS, and it takes in basic SQL queries and stores the data as XML...

Since it's SQL, you can easily port small mysql php scripts to dbx and run them rightaway... it's also perfect for small sites that have php, but dont have MySQL.

We've put in quite some work into this, and would like people to use it - it's freely available for download at:

http://dbx.idya.net

(note the download form of the site - it runs on DBX!!!!) 🙂

[deleted]

It's always good to know about new products, but yet another attempt at a text-based database?

It's a nice idea (if somewhat redundant when mysql is so small and convenient), but why on earth (I actually mean "why in the name of zeus's butthole") did you choose to store the data in the very insuitable, overhead-happy, please-don't-use-me-for-a-database, XML format? (the worst possible choice for storing non-distributed data)

If I store 9 times 4 fields of 7 bytes each, that's 216 chars which your XML explodes into 1382 bytes, the datafile is 6.5 times the amount of data. XML is not a good choice.

Some other notes/questions;
I only see an flock() function when you write the XML, does that mean two scripts can read the same XML file, process it, and then each write their own version of the same file back to disk, overwriting eachothers changes?

And you may want to add a load more error checking, you lock the file without checking wether it was actually locked.

I tried to insert 1000 rows in one go (gotta be nasty hehe ), and ofcourse I got the infamous 30 second timeout. No problem, a flatfile database can't be fast, but, when I tried again, I got an XML error, the timeout left the XML file corrupt.
so I removed the time limit, created a new database and tried again, but after the inserts I again got a corrupt XML file.
Nasty, because the entire file becomes useless.

Oh, and this is in your manual:

"Change the file permissions of the DB directory to 0777. All database will be stored in this directory."

this is not an option, take it out or change it to something better.

Anon

hmm...

First of all thanks for taking out the time for atleast trying DBX.

A few words about the download mechanism - when you give your email and username(I think you entered junk text, vincent) it gets stored in a DBX database using an insert query.

there've been quite a lot of downloads so far, and I think the database is handling it quite well - no corrupt XML that I can see here.

we chose XML because it allows us to store data very easily - otherwise DBX would be twice its present size.

Yes, we all know that mySQL is free, small and efficient - I use it on all my sites myself, but if you look at the many people who don't have mySQL installed but want SQL scripts to run, it is an advantage don't you think?

btw, thanks for the pointers - we're trying to incorporate the infamous "dirty read" problem that you mentioned...

[deleted]

"I think you entered junk text, vincent"

Guitly as charged. Dang, ip logging too.. nasty 🙂

"there've been quite a lot of downloads so far, and I think the database is handling it quite well - no corrupt XML that I can see here."

Indeed DBX works quite well, and I'm sure it can handle a fair amount of data in total, it's just that textfiles (and therefore XML files too) are famous for not being able to handle high-concurrency situations, you get into all sorts of interesting locking issues because files basically have one locking method and that's an excusive lock on the entire file (and therefor implicitly the entire database).

Now I know DBX is designed for small sites, but even small sites can get two concurrent requests, which means DBX must be able to handle that properly.

"we chose XML because it allows us to store data very easily"

Don't you mean "we chose XML because we already had an XML routine so we didn't have to spend time writing a new one"? 🙂

If you write your own data storage routines you'd be able to store data just as easily as with the current XML routines. 🙂

"otherwise DBX would be twice its present size"

I doubt that very much, because not using XML means you nolonger have to write your data in the hiddeously complex XML format (which is ok for complex data, but databases have simple rows like "field1;field2;field3". The number of fields and the order of the fields are always the same, which means XML is just using your resources to add useless field information to the file. And that makes the datafiles grow and your application slow. (Poetic stuff eh ? 🙂 )

I think a custom routine may actually be smaller.

"but if you look at the many people who don't have mySQL installed but want SQL scripts to run, it is an advantage don't you think?"

Definately, it's nice to be able to use simple (very simple) SQL to access the textfile data. Saves us a fair bit of work writing custom routines for the ordering 🙂

It has the potential to be a good mysql alternative for those who can't get mysql and don't need any 'real' SQL functionality.

Do you have plans to implement more SQL functions, like JOINs?

Anon

joins? well, that'll be too much 🙂

Our next step is to make the querying more efficient and faster...

about XMLfile... we're actually using XML because of the ease of manually editing a datafile.... it's so easy and convenient to simply take a file and "write out" your record (since the XML format is sorta self expanatory). Much fasetr than querying...

btw, vincent, thanks for all the criticizm.. you've been great help!!!