is it possible to eager load m2m relation with objects?

[keinagae]

I want to use objects as i need data in instance form not in dict form i am unable to eager load an m2m relation is it possible to do that with objects or is there way to use instance with select instead of dict?

[dantownsend]

I don't think so. You can get objects using get_m2m: https://piccolo-orm.readthedocs.io/en/latest/piccolo/schema/m2m.html#get-m2m. To get it all in one go, you can use select: https://piccolo-orm.readthedocs.io/en/latest/piccolo/schema/m2m.html#select-queries

I think what you're after is something like:

class Band(Table):
    name = Varchar()
    genres = M2M(LazyTableReference("GenreToBand", module_path=__name__))


class Genre(Table):
    name = Varchar()
    bands = M2M(LazyTableReference("GenreToBand", module_path=__name__))


# This is our joining table:
class GenreToBand(Table):
    band = ForeignKey(Band)
    genre = ForeignKey(Genre)


>>> bands = await Band.objects(Band.genres)
>>> band[0].genres
[<Genre 1>, <Genre 2>]

Unfortunately we don't have an API like that at the moment. I can see it being useful though, so I'll try and add it at some point. Sorry about that.

[keinagae]

for select i am getting dicts not model instance is it possible to load in stance from select?

[dantownsend]

Not at the moment - if you want to turn them into objects, you could iterate through the response and turn them into objects:

[MyTable(**i) for i in m2m_rows]

[sinisaos]

Unfortunately, it doesn't work. A ValueError was raised for unrecognized m2m columns from Table init. I think the best way (as you already wrote) is to use get_m2m in two go. Something like this

>>> bands = await Band.objects()
>>> {band.name: await band.get_m2m(Band.genres) for band in bands}
{'Band 1': [<Genre: 1>, <Genre: 2>], 'Band 2': [<Genre: 1>]}
>>> genres = await Genre.objects()
>>> {genre.name: await genre.get_m2m(Genre.bands) for genre in genres}
{'Genre 1': [<Band: 1>, <Band: 2>], 'Genre 2': [<Band: 1>]}