SQLAlchemy add columns to query() on mapped class

Question

I'm wanting to do pagination, I'm using PostgreSQL. To avoid doing the query twice, I'm using the feature described at https://stackoverflow.com/a/8242764

How can I add the full_count column to the list of columns fetched in my query. I can use query.add_columns, but that column is not accessible after calling query.all()

Is this possible in SQLAlchemy?

rkhayrov · Accepted Answer · 2013-08-01 05:17:12Z

4

Can you provide the original code for the query you want to augment? Are you using SQLAlchemy core or declarative ORM? For the latter it will look like this:

from sqlalchemy import func

items = session.query(Model, func.count().over().label('full_count')).all()
obj = items[0].Model
count = items[0].full_count

answered Aug 1, 2013 at 5:17

rkhayrov

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3 Comments

axon Over a year ago

I'm not sure what I was doing before, but it definitely wasn't what you've suggested. Your solution was exactly what I needed.

shroud Over a year ago

Is there a way to do this where the 'full_count' field gets placed directly on the Model? So items[0] would return the same as items[0].Model in your example above, except that items[0].full_count would contain the result of the func.count()?

Nick K9 Over a year ago

You may be able to get what you want using query-time SQL expressions. Here's an example.

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