Hello,
I want to use a table and ORM for keeping and managing tree of static web
pages with MPTT approach. The class/table itself is rather simple:
class Node(db.Model):
__tablename__ = 'node'
id = db.Column(db.Integer, primary_key = True)
parent_id = db.Column(db.Integer, db.ForeignKey(id))
name = db.Column(db.String(150), nullable = False)
urlname = db.Column(db.String(150), nullable = False)
lft = db.Column(db.Integer, nullable = False)
rgt = db.Column(db.Integer, nullable = False)
here urlname is the part of full URL a page has, e.g. if we have a page
Presentations with a list of presentations, with parent page Library and
available at '/library/presentations', the 'urlname' for this record will
be 'presentations' and urlname for the parent page, Library, will be
'library'. However in this case, every time I need a full URL to the page I
have to make a query to get it. In standard SQL I can get a list of pages
with pseudo field 'url' as following:
select n1.name, (select group_concat(n2.urlname SEPARATOR '/') from node n2
where n2.lft <= n1.lft and n2.rgt >= n1.rgt order by n2.lft asc) as url
from node n1
Is there any way to make SQLAlchemy select this pseudo field automatically
every time I make a query or fetch an object? Say I do something like n =
Node.query.filter(name = 'Presentations') and then just use n.url?
Thanks a lot in advance for any hints!
Sergey
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