Databases
StackOverflow2013
Postsdbo
POTransforming data when saving and reading from database
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POTransforming data when saving and reading from database
    primarykey
    data
    text
    <p>Suppose I have this model (not real code):</p> <pre><code>class Message(models.Model): content = models.CharField(...) mentions = models.ManyToManyField(User) </code></pre> <p>content can for instance be: </p> <blockquote> <p>Say hi to @Adam and @Bernard</p> </blockquote> <p>During the Message model save(), "Adam" and "Bernard" are extracted from the text, and their respective user instances added to mentions, so that</p> <pre><code> &gt;&gt;&gt; m = Message.objects.create(content="Say hi to @Adam and @Bernard") &gt;&gt;&gt; m.mentions.all() &gt;&gt;&gt; [User: Adam, User: Bernard] </code></pre> <p>Now, as to my problem:</p> <p>How do I cope with Bernard performing a sex-change and renaming himself Bernarda? I would very much like the content then to read <code>Say hi to @Adam and @Bernarda</code>.</p> <p>Basically, I've tried a strategy of replacing names with ID's when saving (<code>Say hi to @Adam and @Bernard</code> then becomes <code>Say hi to @1 and @2</code>, i.e. their User.pk's). This works fine when saving, and OK-ish when reading. </p> <p>Doing this replacement in the model's save() method works fine, but read and lookup operations are a major problem. I cannot find an easy way of making sure that what is stored in the database (ie <code>Say hi to @1 and @2</code>) 'magically' becomes <code>Say hi to @Adam and @Bernard</code> whenever it is being queried (be that through .filter() and related operations) or its instance being evaluated.</p> <p>I'm unsure whether I'm on the right track here; any pointers or ideas to doing this differently are very welcome!</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USjpic
    1. USLaundroMat
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POTransforming data when saving and reading from database
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POTransforming data when saving and reading from database
      1. USjpic
      1. VTFavorite
    1. COGood question, but can you give an example of what type of filter you are trying to achieve? Why is it necessary to have the names in the string when filtering, if you already have the mentions available in another field?
      singulars
      1. POTransforming data when saving and reading from database
      1. USHerman Schaaf
    2. COThe filter (or any query) would come in handy when checking for uniqueness for example: in my case, I don't want two messages that are exactly alike.
      singulars
      1. POTransforming data when saving and reading from database
      1. USLaundroMat
    3. COThen why not pass unique=True to the content CharField constructor ?
      singulars
      1. POTransforming data when saving and reading from database
      1. USjpic
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload