Hmm.. I see what you're saying, but the column can be from any of the
tables queried from, not just the Study table. So it could be
Study.study_id, System.system_name, Site.site_id, etc. Also won't that
getattr() call just return a string? I was under the impression that you
had to pass a column object to order_by(). So if implemented the solution
for dynamic sort direction given in the stackoverflow link above (which
takes advantage of the fact that you can access the .asc() or .desc() methods
as attributes on the column object), I have this:
def my_query(sort_direction='asc'):
column_sorted = getattr(Study.study_id, sort_direction)()
query = Study.query.options(
db.joinedload(Study.system),
db.joinedload(Study.site)).\
filter(System.system_id==41).\
order_by(column_sorted)[start:end]
return query
How can I modify this so that it doesn't just sort on Study.study_id and my
method signature would be my_query(sort_column, sort_direction)?
Maybe this isn't possible using the ORM and I have to dip down into the SQL
expression language, but I thought I'd ask.
Thanks.
On Thu, Feb 13, 2014 at 7:08 PM, Michael Bayer <[email protected]>wrote:
>
> On Feb 13, 2014, at 6:21 PM, Tony Garcia <[email protected]> wrote:
>
> > Hello,
> > I'm new to SQLAlchemy and have searched high and low for a solution to
> my problem so I'm hoping someone here can help. I have a query where I need
> to apply the 'order by' clause dynamically (both the column and the
> direction). So a 'static' version of my query would be:
> >
> > studies = session.query(Study).options(
> > joinedload(Study.system),
> > joinedload(Study.site)).
> > filter(System.system_id=41).
> > order_by(Study.study_id.desc()).
> > all()
> >
> > However the order can be asc or desc and it could be any column from the
> 3 tables. I found this post on Stackoverflow which helps with a dynamic
> sort direction (asc, desc), but it doesn't help me with the dynamic column:
> >
> >
> http://stackoverflow.com/questions/20904226/python-sqlalchemy-dynamic-order-by
>
> "dynamic" attribute access in Python is using the getattr() builtin
> function:
>
> def my_query(order_by_column):
>
> query =
> session.query(Study).filter(Study.system_id=41).order_by(getattr(Study,
> order_by_column))
>
> that seems like what you're asking, hope it helps.
>
>
>
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