I am not that experienced with django yet, but we are creating a project soon and we were wondering which database to use for our backend (Mongodb or PostgreSQL).
I've read a lot of post saying the differences between each, but I still can't take the decision of which to go for. Taking in consideration I never worked with Mongodb before.
So what shall I go for ??
Thanks a lot in advance
MongoDB is non-relational, and as such you cannot do things like joins, etc.
For this reason, many of the django.contrib apps, and other 3rd-part apps are likely to not work with mongodb.
But mongodb might be very useful if you need to store schemaless complex objects that won't go straight into postgresql (of course you could json-serialize and put in a text field, but using mongodb instead is just way better, allows you doing searches, ..).
So, the best suggestion is to use two databases:
PostgreSQL for the standard applications, such as django core, authentication, ...
MongoDB only for your application, when you have to store non-relational, complex objects
You also might want to use the raw_* methods that skip lots of (mostly unnecessary) validation by the django orm.
Just remember that databases, especially sql vs no-sql, are not drop-in replacements of each other, but instead they have their own features, pros and cons, so you have to find out which one suits best your needs in each case, not just pick one and use it for everything.
UPDATE
I forgot to say: remember that you have to use the django-nonrel fork in order to make django support non-relational databases. It is currently a fork of django 1.3, but a 1.4-based version is work-in-progress.
Related
Recently we are working with Rails Now want to attach module working with Django. Can We use same data Base for both project. Secondly postgresql db is used here.If any framework or gem present that can handle this.
The cool thing about a general-purpose relational database (or actually one of the many cool things) is that you can use it with all kinds of programming environments – all you need to do is use the proper driver. So that should be no problem technically.
If the two programs work on the same data, let them share the database. If they operate on different data, create a new database.
I know some ways like scrapy-djangoitem but as it has mentioned:
DjangoItem is a rather convenient way to integrate Scrapy projects with Django models, but bear in mind that Django ORM may not scale well if you scrape a lot of items (ie. millions) with Scrapy. This is because a relational backend is often not a good choice for a write intensive applications (such as a web crawler), specially if the database is highly normalized and with many indices.
So what is the best way to use scraped items in db and django models?
It is not about Django ORM but rather about the database you choose as backend. What it says is that if you are expecting to write millions of items to your tables, relational database systems might not be your best choice here (MySQL, Postgres ...) and it can be even worse in terms of performance if you add many indicies since your application is write-heavy (Database must update B-Trees or other structures for keeping index on every write).
I would suggest sticking with Postgres or MySQL for now and look for another solution if you start to have performance issues on database level.
Django community seems to encourage the use of Postgres, I understand that in a big project you probably don't want to use SQLite or such, but i don't know why they don't like Mysql that much.
just a quick example - Djangobook page 9:
We’re quite fond of PostgreSQL ourselves, for reasons outside the scope of this book, so we mention it first. However, all those engines will work equally well with Django.
Postgres name is always associated with Django - just like Mysql is always associated with php
Best answer might be given to this quiestion is from those who writes the Framework...
But from what you can get from documentation is:
By default, Django starts a transaction when a database connection is first used and commits the result at the end of the request/response handling. The PostgreSQL backends normally operate the same as any other Django backend in this respect.
Django have a strong Transection control, and using a powerful free DBMS that have strong transection control is a plus...
Also, previous versions of Mysql (before mysql 5.0), MySql have some integrity problems. Also MySql's fast storage engine MyISAM do not support foreign keys and transections. So using MyISAM have important minuses that its pluses...
And a wiki for why Postgres is better than Mysql. Its quite old but it is good.
I have never used PostgreSQL myself, so I can't really say much about the advantages it is supposed to have over MySQL.
But from what I've gathered, transaction handling is better supported by PostgreSQL out of the box. If you use MySQL, changes are that you will use MyISAM as storage engine, which doesn't support transactions.
https://docs.djangoproject.com/en/dev/topics/db/transactions/#transactions-in-mysql
Maybe the Django devs just got sick and tired of having to deal with bug reports where transactions didn't work, but the problem was due to MyISAM and not Django.
The South developers (the most used database schema migration framework for Django) apparently aren't to fond of MySQL either, which this message suggests that I've seen quite often with MySQL:
! Since you have a database that does not support running
! schema-altering statements in transactions, we have had to
! leave it in an interim state between migrations.
[...]
! The South developers regret this has happened, and would
! like to gently persuade you to consider a slightly
! easier-to-deal-with DBMS.
I've always used Postgres whenever possible, partly because of maturity and because of the PostGIS extensions that add spatial data capabilities to the database. Even if I don't think I'm going to want spatial data in my application at the beginning its much easier to add it on if your DB supports it, rather than have to tear out MySQL at a late stage and replace it with PostGIS.
I think there is a spatial extension to MySQL now, so you might be able to do spatial operations in that now. But Postgres just does it and has been doing it for years.
Or I could spend $$$$$ for Oracle Spatial, I suppose...
i'm new to the nosql world, and from forums and articles that i've read: most of users try to "mix" nosql tools, for example, they use Cassandra and MongoDB together to make a "powerful system", because am beginning with MongoDB, i've downloaded the DjanMon project (am a django fan ^_^ ), of course i've downloaded the special version of django that accepts the NoSql use: Django NonRel, and i've noticed that the Setting file dont "oblige" you to use one specific NoSql solution like in Django with RDBMS where you must specify MySql or PostegreSql or other solution, so, is it possible to mix lot of (or two of course) NoSql solution using Django (for example MongoDB+Cassandra)?
There's nothing to stop you using multiple storage solutions, whether SQL or NoSQL - but the NoSQL solutions all have different architectures, data models and APIs (For example, MongoDB is a document-oriented database, whereas Cassandra is Column-oriented), so you can't usually swap one for another without some effort.
Can you clarify what you are actually trying to achieve? I.e. why are you interested in mixing these two specific solutions?
Django (http://djangoproject.com) framework currently supports the following databases: PostgreSQL, SQLite 3, MySQL 5 and Oracle. This question is not about the comparison of these databases, contrariwise I want to know details about their compatibility with Django and how one should choose an adequate database for a simple (but growing) project.
It depends. If you don't want to pay the (huge) premium for Oracle, your choice is between MySQL and PostgreSQL (SQLite is mostly meant for development, not production). PostgreSQL seems to be the choice of most Django core devs (Andrew Godwin went as far as putting "friends don't let friends use MySQL" into a DjangoCon talk). Nevertheless, MySQL is fully supported by Django and is used by many Django websites in production.
IMHO, PostgreSQL has two clear advantages over MySQL:
If you use GeoDjango. There's really no alternative to PostGIS. MySQL's GIS support is lackluster at best.
South. MySQL is not able to use transactions during schema migrations, which means if a South migration goes awry, you're hanging between two migrations without clear way forward or backward. PostgreSQL saves a lot of pain in such situations.
The quick answer is it doesn't really matter but if I had to pick one, it would probably be PostgreSQL.
The original Django developers heavily recommended PostgreSQL in the early days. PostgreSQL is arguably/technically a 'better' database then MySQL so if you've never used it before it might be worth investing some time to lean it.
Now-a-days though I'd say it's safe to assume that all the DB drivers work equally well. So if you are more familiar with MySQL or Oracle there should be no problems using them instead. I've only used Django with MySQL and haven't had any problems.
All of the pluggable databases are supported, meaning, the the model/db-layer will abstract the db-specifics for you. As for performance, I'd suggest MySQL 5 or Postgresql. Oracle will definitely perform well, but might be more expensive in the long run. If you are just started your project, sqlite3 is your friend, simply because the it will be setup within seconds.
Handling parallel settings for development and production has been discussed in various blog posts, e.g. in this one:
http://ericholscher.com/blog/2011/jan/10/handling-django-settings-files/