MongoDB & web2py: Working with ObjectIds

Question

I'm working on a very simple application as a use case for integrating MongoDB with web2py. In one section of the application, I'm interested in returning a list of products:

My database table:

db.define_table('products',
Field('brand', label='Brand'),
Field('photo', label='Photo'),
...
Field('options', label='Options'))

My controller:

def products():
qset = db(db['products'])
grid = qset.select()
return dict(grid=grid)

My view:

{{extend 'layout.html'}}
<h2>Product List</h2>
{{=grid}}

The products are returned without issue. However, the products._id field returns values in the form '26086541625969213357181461154'. If I switch to the shell (or python) and attempt to query my database based on those _ids, I can't find any of the products.

As you would expect, the _ids in the database are ObjectIds that look like this '544a481b2ceb7c3093a173a2'. I'd like to my view to return the ObjectIds and not the long strings. Simple, but I'm having trouble with it.

Anthony · Accepted Answer · 2014-10-28 20:19:14Z

1

When constructing the DAL Row object for a given MongoDB record, the ObjectId is represented by converting to a long integer via long(str(value), 16). To convert back to an ObjectId, you can use the object_id method of the MongoDB adapter:

object_id = db._adapter.object_id('26086541625969213357181461154')

Of course, if you use the DAL to query MongoDB, you don't have to worry about this, as it handles the conversion automatically.

answered Oct 28, 2014 at 20:19

Anthony

25.5k3 gold badges31 silver badges58 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

datasci · Accepted Answer · 2014-10-29 14:11:50Z

1

Although it makes perfect sense, I wasn't able to make Anthony's answer work. So, I just hacked it:

hex(value).replace("0x","").replace("L","")

answered Oct 29, 2014 at 14:11

datasci

1,0292 gold badges13 silver badges30 bronze badges

1 Comment

Anthony Over a year ago

Hmm, not sure why db._adapter.object_id doesn't work for you, but in any case, it just ends up doing hex(arg)[2:].rstrip('L').zfill(24), so mostly the same as your code.

Collectives™ on Stack Overflow

MongoDB & web2py: Working with ObjectIds

2 Answers 2

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related