On Wed, Jan 8, 2014 at 3:37 PM, Mark S dbs...@gmail.com wrote:
Hi
I can successfully use pagination with the following -
mydata=Article.query.filter(Article.author_id==User.id).filter(User.id==g.user.id).paginate(page,
POSTS_PER_PAGE, False)
However, I need to fetch columns from multiple tables. In that case how can
I modify the code above in order to use pagination?
Here is what I need to do -
mydata = db.session.query(id,title,Author).from_statement(\
SELECT
a.id,a.title,u.author \
FROM article a, user u\
where a.user_id=u.id \
and u.id=:userid)\
.params(userid=g.user.id).all()
However, with this , pagination does not work and I get an error -
AttributeError: 'Query' object has no attribute 'paginate'
Can you please help?
There are a couple of options. One would be to configure your
db.session object to use the Flask-sqlalchemy query class, rather
than the default SQLAlchemy one. The Session class constructor has a
query_cls parameter for this purpose - you'd want to pass
flask_sqlalchemy.BaseQuery. I don't use Flask, so I don't know how
your session is currently being configured.
Another option would be to use the with_entities method of Query to
change the set of columns that are being queried for:
http://docs.sqlalchemy.org/en/rel_0_9/orm/query.html#sqlalchemy.orm.query.Query.with_entities
so you could write something like Article.query.with_entities('id',
'title', 'Author').from_statement(...)
But I guess what you are really trying to do is to query Articles, but
only to load certain columns. You might be interested in using
load_only instead:
http://docs.sqlalchemy.org/en/rel_0_9/orm/mapper_config.html#load-only-cols
which is part of a bigger topic about deferred column loading:
http://docs.sqlalchemy.org/en/rel_0_9/orm/mapper_config.html#deferred-column-loading
Hope that helps,
Simon
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