Hello the Community,
imagine we have a tree-like dictionary:
class IndustrySector(Entity):
name = Field(Unicode(128),required=True,unique=False)
parent = ManyToOne('IndustrySector',required=False)
using_table_options(UniqueConstraint('name','parent_id'))
Top-level items have parent_id of NULL; an example is a top-level item
'IT' and sub-items 'Software development', 'Outsourcing', while
'Software development' has sub-items of 'Linux kernel development',
'Web application development', etc.
Next, we have a Company entity:
class Company(Entity):
name = Field(Unicode(128), required=True,
nullable=False)
industry_sector = ManyToOne(IndustrySector, required=True)
that is linked to the IndustrySector dictionary.
What is the *right* way to:
1) get the top-level IndustrySector? For example, if 'My Company' has
it's indusrty_sector set to 'Linux kernel development', we'll get 'IT'
as a top-level; I'd suppose to add a read-only property to the Company
entity that selects industry_sector.parent until is is None; Say we
name it 'top_level_industry_sector';
1a) get a list of all industry sectors, from bottom to top; in the
example above, this will return a list of 'Linux kernel development',
'Software development', 'IT'
2) query all the Company that have a required top-level industry
sector? Well, something like
DBSession.query(Company).filter(top_level_industry_sector=1) will go
or not?
It seems it's quite simple to implement these methods but maybe
there's a well-known solution/pattern already and I should not invent
the wheel? :)
Thanks in advance!
--
Sergei.
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