When To Use MySQL Cursor Classes In Python

18 Jan 2010 — eric

I have been writing a lot of code that has been interacting with MySQL lately. Sometimes I find it easier to work the result set in a dictionary form and other times it is easier with an array. But in order to not break all your code, it is necessary to set a default cursor class that keeps your code consistent. More often than not, I find using using a arrays is easier since I just want quick access to all the retrieved data. I also end up making my SELECT calls while specifying the columns and order of the columns I want returned.

The reason that using cursor classes is handy is because Python doesn’t come with a mysql_fetch_assoc like PHP or selectrow_hashref like Perl’s DBI interface. Python uses cursor dictionaries to bridge this gap. Ultimately your result is the same. But as with Perl and PHP, defaulting to cursor dictionaries isn’t a good idea for larger datasets because of the extra processing time and memory required to convert the data.
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Migrations Without belongs_to Or references

14 Oct 2009 — eric

Normally when do a database migration in Rails, when adding ownership from a model to another model, you use the concept of belongs_to or references:

  create_table :comments do |t|
    t.belongs_to :user
    t.references :post
  end

Interestingly enough, these methods are only available during the initial table creation. If you want to add a reference to a model that is created later, you have to do it the old fashioned way, by just adding a column:

   add_column :comments, :group_id, :integer

Doing it this way is clean, easy, and definitely meets the KISS principle. But I do find it interesting that one can’t add an association later in the game. Sometimes the Rails way is just KISS and adding the column by hand.

Posted in Rails. Tags: . No Comments »
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