Hi Folks,
So we have a sort of generic table; let's call it 'Thing'. For the sake of
example, let it have two columns. An integer 'id', and a hstore 'data':
from sqlalchemy.dialects.postgresql import HSTORE
from Column, Integer
class Thing(Base):
__tablename__ = 'thing'
id = Column(Integer, primary_key=True)
data = Column(MutableDict.as_mutable(HSTORE))
Now what I want to do is have some more mapped attributes that peek inside
the HSTORE. I am assuming I know something about the HSTORE structure when
I add this to the class definition:
foo = column_property(expression.cast(data["foo"], Integer))
And this works pretty well; when I get an instance of Thing, I can ask it
for it's 'foo' and I get an integer back.
However it doesn't work if I *assign* to foo. The session notices the
object is dirty but doesn't know how to write back my changes.
In an earlier attempt at this I just made 'foo' a hybrid property which
wrote and read directly into the data 'hstore', doing the casting at each
read/write. This was OK for integers and strings but what I really want to
say is something like:
bar = column_property(expression.cast(data["bar"], *JSONEncoded*))
And be able to do:
mything.bar.append("lalala")
(Here I am assuming that I had a HSTORE with a key 'bar' with a value that
was a JSON encoded list)
(JSONEncoded is a custom mutable type similar to examples in the docs).
So I'd like to be able to use mutable types; not just reassignment. Perhaps
I need some custom types and a reimplementation of column_expression to
fetch/write to the HSTORE but I am getting a bit lost!
Anyone tried anything like this before?
All the best,
Philip
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