SqlAlchemy - How to query a table based on a key property saved as NestedMutableJson - database

Question

Let suppose a Postgres user table contains a property of type NestedMutableJson.
first_name character varying (120)
last_name character varying (120
country_info NestedMutableJson
...
from sqlalchemy_json import NestedMutableJson
country_info = db.Column(NestedMutableJson, nullable=True)
country_info = {"name": "UK", "code": "11"}
How to query the user table based on a country_info key.
POSTGRES Query
SELECT * FROM user WHERE country_info ->> 'name' = 'UK'
Does any SqlAlchemy way give the same query result?
I tried several ways, example:
Way 1:
User.query.filter(User.country_info['name'].astext == 'UK').all()
Error:
Operator 'getitem' is not supported on this expression
Way 2:
User.query.filter(User.country_info.op('->>')('name') == 'UK').all()
Issue:
Always getting an empty response
I'm wondering if the issue caused by the column definition db.Column(NestedMutableJson, nullable=True)
I'm avoiding using db.session.execute("SELECT * FROM user WHERE country_info ->> 'name' = 'UK'").fetchall(). looking for something else

Answer 1

simply user the text which allows you to write plain text filter inside orm process, it works like get function for a dict, and it can handle None fields also.
User.query.filter(text("COALESCE(user.country_info ->> 'name', '') = 'UK'")).all()
note that the name of the table should be the real name in the database

Answer 2

Take a look at the JSON datatype documentation.
You should be able to do use this filter clause
select(CountryInfo).filter(CountryInfo.country_info['name'].astext == "UK")

Answer 3

You can use .op('->>') to use the PostgreSQL operator ->> in the following way:
from sqlalchemy import Column, Integer, create_engine, String, select
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import Session
from sqlalchemy.dialects.postgresql import JSON
from sqlalchemy_json import NestedMutableJson
dburl = 'postgresql://...'
Base = declarative_base()
class CountryInfo(Base):
__tablename__ = 'country_info'
id = Column(Integer, unique=True, nullable = False, primary_key=True)
name = Column(String)
country_info = Column(NestedMutableJson, nullable=True)
def __repr__(self):
return f'CountryInfo({self.name!r}, {self.country_info!r})'
engine = create_engine(dburl, future=True, echo=True)
Base.metadata.drop_all(engine)
Base.metadata.create_all(engine)
with Session(engine) as session:
test = CountryInfo(name='test', country_info={"name": "UK", "code": "11"})
test2 = CountryInfo(name='test2', country_info={"name": "NL", "code": "12"})
test3 = CountryInfo(name='test3', country_info={"name": "UK", "code": "13"})
session.add(test)
session.add(test2)
session.add(test3)
session.commit()
stmt = select(CountryInfo).filter(CountryInfo.country_info.op('->>')('name') == "UK")
query = session.execute(stmt).all()
for row in query:
print(row)
This results in the following SQL:
SELECT country_info.id, country_info.name, country_info.country_info
FROM country_info
WHERE (country_info.country_info ->> %(country_info_1)s) = %(param_1)s
with {'country_info_1': 'name', 'param_1': 'UK'}
Which results in:
(CountryInfo('test', {'name': 'UK', 'code': '11'}),)
(CountryInfo('test3', {'name': 'UK', 'code': '13'}),)