SQLAlchemy update PostgreSQL array using merge not work

Question

I\'m using SQLAlchemy to access PostgreSQL database, and I defined the object like this:

class SessionLog(Base):
    __tablename__ = \'session_log\'

    id          


        

Answer 1

Found this gist which helped me a lot. I added a custom __setitem__ to be able to change an item in the list, and __delitem__ to delete one:

from sqlalchemy.ext.mutable import Mutable
from sqlalchemy.dialects.postgresql import ARRAY

class MutableList(Mutable, list):

    def __setitem__(self, key, value):
        list.__setitem__(self, key, value)
        self.changed()

    def __delitem__(self, key):
        list.__delitem__(self, key)
        self.changed()

    def append(self, value):
        list.append(self, value)
        self.changed()

    def pop(self, index=0):
        value = list.pop(self, index)
        self.changed()
        return value

    @classmethod
    def coerce(cls, key, value):
        if not isinstance(value, MutableList):
            if isinstance(value, list):
                return MutableList(value)
            return Mutable.coerce(key, value)
        else:
            return value

Then in your model:

your_field = db.Column(
    MutableList.as_mutable(ARRAY(db.String())),
    server_default="{}"
)