Check it out… I was mentioned in a recent Nature article about research paper management tools:

http://www.nature.com/news/2008/080430/full/453012b.html (doi:10.1038/453012b)

Cool, eh?

I wanted a simple GTK-based LaTeX editor with spell checking, syntax highlighting and a preview pane. None that I could find fit this bill, so I rolled my own.

Website: http://desigle.org/

Use if you wish.

My PyGTK skillz are improving…

Allow me to introduce gPapers, a Gnome-based Digital Library Manager. (think iTunes for all your PDF files)

If you have to ask “why?”, you’re probably not working in academia, and have never had to manage piles of journal papers. This isn’t for you. If you’re a Windows or OSX user, this isn’t for you. If you’re afraid of compiling a library or two, this isn’t for you. In fact, I believe there is a worldwide audience of perhaps seven people who will find this software useful.

But to those six others, I promise it’s a godsend.

This has been a side project for me for a little over a month now, and I’m ready to start collecting external feedback. So please, give it a whirl (and join the listserv).

So I bought a Nokia N800, initially so I can work on a mobile version of allurstuff, but also I’m curious if I can get android working on it… But while I’m waiting for FedEx to deliver, I decided that it needed a way to access Google Maps even without an internet connection.

And so was born ogmaps. It’s a fairly simple python script that downloads all the HTML/Javascript/image files used by gmaps, and modifies them to run right off your hard drive. (or flash drive, whatever) It then looks up whatever location you give it, and caches all the surrounding map files. (within reason….grabs about 5-10mb of data for each location you give it)

You don’t need a handheld to use it either… It’ll work wherever you have python and firefox. (I haven’t tried it with IE yet, and likely won’t - get a better browser!)

Anyway, tell me what you think.

derek

Google has announced their “gPhone”, and it’s a open, Linux-based software platform called Android:

• watch their intro video

And they’re celebrating by also announcing a $10 million developer challenge, two be handed out in two $5 million dollar rounds with at least 50 individual recipients each round. Pretty exciting, eh?

So does anyone have any suggestions for “i wish my phone could do this”? I’d love to hear your thoughts…

If you’re not familiar with Apple’s Time Machine, it’s a backup system that lets you browse using historical snapshots of what your system used to look like. It’s pretty neat, but I use Linux, not MacOSX. So I rolled my own.

http://code.google.com/p/flyback/

Just an update on my former SoC2006 work…

We now no longer require a patch to Django. One import statement in settings.py allows our program to fake it via the very crafty Python language.

The new website is here: http://code.google.com/p/deseb/
The discussion list us here: http://groups.google.com/group/deseb-discuss

Plus there is an introductory video available here: http://kered.org/deseb_demo.mpeg

A concern of my schema evolution solution is as follows:

The ‘aka’ approach has some serious flaws. It is ambiguous for all but trivial use cases. It also doesn’t capture the idea that database changes occur in bulk, in sequence. For example, On Monday, I add two fields, remove 1 field, rename a table. That creates v2 of the database. On Tuesday, I bring back the deleted field, and remove one of the added fields, creating v3 of the database. In each stage of the migration, the DB is a stable state; this approach doesn’t track which state a given database is in, and doesn’t apply changes in blocks appropriate to versioned changes.

The fallacy in this is twofold:

1. that an automated introspection/evolution must generate and apply schema changes in the same logical order that a DBA would
2. that keeping intermediate state metadata is always necessary (obviously required from #1)

I argue that the exact path from v1 => v3 is irrelevant, as long as it is functionally equivalent to the DBA generated one, and minimizes information loss. To demonstrate this, I’ve coded the above example into three different models.py files:

from django.db import models

class Russ(models.Model):
    "this model is going to have a bit of a day (v1)"
    a = models.CharField(maxlength=200)

from django.db import models

class WasRuss(models.Model):
    "this model is going to have a bit of a day (v2)"
    b = models.CharField(maxlength=200)
    c = models.CharField(maxlength=200)

    class Meta:
        aka = ('Russ')

from django.db import models

class WasRuss(models.Model):
    "this model is going to have a bit of a day (v3)"
    a = models.CharField(maxlength=200)
    b = models.CharField(maxlength=200)

    class Meta:
        aka = ('Russ')

Now let’s assume we have three users: Alice, Bob and Charles. Alice is the developer and Bob and Charles are sys-admins, deploying her application.

On day one, Alice writes her new model (v1) and calls syncdb to create it as you normally would. She then adds data to the table for testing. But on day two, she decides that her original implementation is inadequate and makes her modifications (v2). But instead of writing and storing her own migration scripts or just tossing all her data, she runs sqlevolve, which gives her the following:

ALTER TABLE `case06_russ_russ` RENAME TO `case06_russ_wasruss`;
ALTER TABLE `case06_russ_wasruss` ADD COLUMN `b` varchar(200) NOT NULL;
ALTER TABLE `case06_russ_wasruss` ADD COLUMN `c` varchar(200) NOT NULL;
-- warning: the following may cause data loss
ALTER TABLE `case06_russ_wasruss` DROP COLUMN `a`;
-- end warning

Now day three rolls around, and she’s changed her model again (v3). Again she run’s sqlevolve to get the following:

ALTER TABLE `case06_russ_wasruss` ADD COLUMN `a` varchar(200) NOT NULL;
-- warning: the following may cause data loss
ALTER TABLE `case06_russ_wasruss` DROP COLUMN `c`;
-- end warning

Which gets her exactly to where she needs to be: a schema identical to what a fresh sqlall would give, without destroying all her data. (she did lose everything in column a, however this is acceptable because an identical loss would come from the versioned scripts she would have written by hand)

Now Bob is a bleeding-edge kind of guy. He likes to stay on top of Alice’s work daily. So, assuming she’s a timely svn commiter, each day he runs the following four commands:

$ /etc/init.d/apache stop
$ svn update
$ ./manage sqlevolve | mysql -u root -p my_db
$ /etc/init.d/apache start

This deploys to his database in two days the exact same two scripts she ran, including the same information loss in column a.

Now Charles is more of a conservative deployer - he only deploys when Alice gives them notice, which happened at the end of days one and three. On day one, his syncdb created the database to v1’s specifications. However on day three, when he runs the same commands Bob ran, the following is deployed to his database:

ALTER TABLE `case06_russ_russ` RENAME TO `case06_russ_wasruss`;
ALTER TABLE `case06_russ_wasruss` ADD COLUMN `b` varchar(200) NOT NULL;

As you can see, it is a different script than either Alice or Bob ran, however it gets him to a functionally equivalent schema, and it gets him there with less data loss. (he gets to keep his column a information)

Now this can be argued as either a wonderful or horrible thing. Should Charles be forced to dump his column a data? In some really huge, highly critical, heavily deployed production environments, maybe. But I have managed such before, and I think those cases are few and far between. Much more likely the user is going to want to keep their data. But if they do, a simple procedural change is all that’s necessary. Alice needs only to dump her generated evolution SQL into versioned migration scripts, ala Mike Heald’s dbmigration tool.

So to wrap up, I hope I’ve demonstrated that the idea of “database changes must occur in bulk, in sequence” is flawed, and that what is key is schema equivalence , not making sure you can recreate the exact same set of scripts at runtime for all users using all versions. But that if you do need to make sure identical scripts are run by all users, this can be easily done still using the evolution functionality through minor procedural changes in development and deployment.

I should also note that all the scripts used in this article were generated with the code already checked into the schema-evolution branch. I encourage you to try it out for yourself. (and send me bug reports if you find them!)

Thanks,
Derek

I’ve ported my schema evolution work from my SoC project last summer to Django v0.96.   To use it, download the patch below, and run the following:

$ cd /<path_to_python_dir>/site-packages/django/
$ patch -p1 < ~/<download_dir>/django_schema_evolution-v096patch.txt

It should output the following:

patching file core/management.py
patching file db/backends/mysql/base.py
patching file db/backends/mysql/introspection.py
patching file db/backends/postgresql/base.py
patching file db/backends/postgresql/introspection.py
patching file db/backends/sqlite3/base.py
patching file db/backends/sqlite3/introspection.py
patching file db/models/fields/__init__.py
patching file db/models/options.py

To use it:

$ cd /<path_to_project_dir>/
$ ./manage.py sqlevolve <app_name>

It should output something like this:

BEGIN;
ALTER TABLE `main_query` CHANGE COLUMN `accuracy` `accuracynew` numeric(10, 6) NULL;
ALTER TABLE `main_query` ADD COLUMN `price` varchar(256) NULL;
COMMIT;

Assuming you have a model such as this:

class Query(models.Model):
    query = models.CharField(maxlength=256, blank=False)
    accuracynew = models.FloatField(max_digits=10, decimal_places=6, null=True, blank=True, aka='accuracy')
    price = models.CharField(maxlength=256, null=True, blank=True) # new column

Note the aka field where I changed the name of “accuracy” to “accuracynew”.

Source code:

• django_schema_evolution-v096patch.txt

Documentation:

• http://code.djangoproject.com/wiki/SchemaEvolutionDocumentation

Let me know if you find any bugs.

From a guy on /., of all places.

It’s not about communist hippies in Birkenstocks saying everything should be free.   Every web application I build needs a database, an application server and a web server.   On top of that it needs libraries that do a lot of things common to other projects.   It makes no sense for us to take on the burden of developing these from scratch.   It is in our best interest to collaborate with others to build stable, portable solutions that can be deployed en mass without exorbitant licensing fees.

– d3ik