Postgres SQLAlchemy appending to existing jsonb record

Question

I have a postgres DB with a jsonb field data.

I'd like to be able to append to an array of items in the field using sqlalchemy.

For example with the table:

id	data	name
1	[{"jon": {"age": 4}}, {"jane": {"age": 7}}]	paul
2	[{"beryl": {"age": 3}}, {"victor": {"age": 9}}]	dave

To do this in postgres I can use concatenate like this:

UPDATE "test" SET "data" = "data" || '[{"beryl": {"age": 3}}, {"victor": {"age": 9}}]' ::jsonb
WHERE "name"='paul';

Giving:

id	data	name
1	[{"jon": {"age": 4}}, {"jane": {"age": 7}}, {"beryl": {"age": 3}}, {"victor": {"age": 9}}]	paul

I've tried using jsonb_insert in sqlalchemy, but I'm not clear on how to set the path.

I don't want to add the array at a particular key, but want to add to the existing array.

EDIT

The following nests another array inside my existing one, i.e. in the form ['A', 'B'] becomes ['A','B',['C','D']]. I want this to be ['A','B','C','D']

func.jsonb_insert(
    cast(TestObj.data, JSONB), "{-1}", cast(new_records, JSONB), True
)

EDIT 2

Using synchronize_session="fetch" and adding the records in a loop works, but I'm not sure it would be very efficient for a lot of records.

Grateful for any ideas on how to improve this.

for rec in new_records:
    session.query(TestObj).filter(TestObj.name == "paul").update(
        {
            "data": func.jsonb_insert(
                cast(TestObj.data, JSONB), "{-1}", cast(rec, JSONB), True
            )
        },
        synchronize_session="fetch",
    )

Full example code:

import os
from sqlalchemy.dialects.postgresql import JSON, JSONB
from sqlalchemy import func, cast
import sqlalchemy as sa
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base
import urllib
from sqlalchemy.dialects import postgresql
from dotenv import load_dotenv

load_dotenv()

user = urllib.parse.quote_plus(os.environ.get("DB_USER"))
passwd = urllib.parse.quote_plus(os.environ.get("DB_PW"))

DB_URL = "postgresql://{}:{}@{}:{}/{}".format(
    user,
    passwd,
    os.environ.get("DB_HOST"),
    os.environ.get("DB_PORT"),
    os.environ.get("DB_NAME"),
)

engine = sa.create_engine(DB_URL)
Session = sessionmaker(bind=engine, autoflush=True)

session = Session()

Base = declarative_base()


class TestObj(Base):
    __tablename__ = "test"
    __table_args__ = {"autoload_with": engine, "schema": "public"}



initial_data = [
    {
        "jon": {"age": 4},
    },
    {"jane": {"age": 7}},
]

newentry = {"data": initial_data, "name": "paul"}

stmt = postgresql.insert(TestObj).values(newentry)
result = session.execute(stmt)
session.commit()


new_records = [{"bob": {"age": 10}}, {"billy": {"age": 10}}]


for rec in new_records:
    session.query(TestObj).filter(TestObj.name == "paul").update(
        {
            "data": func.jsonb_insert(
                cast(TestObj.data, JSONB), "{-1}", cast(rec, JSONB), True
            )
        },
        synchronize_session="fetch",
    )

session.commit()

A.R.S. · Accepted Answer · 2022-07-12 06:55:05Z

2

In SQLAlchemy, the SQL || operator is the Python + operator. I found this information in this Github issue.

Appending to the existing JSONB array of your example should be something like (untested):

new_records = [{"bob": {"age": 10}}, {"billy": {"age": 10}}]

stmt = (
    sa.update(TestObj)
    .filter_by(name="paul")
    .values(data=TestObj.data + new_records)  # concatenate existing data with new records
)
session.execute(stmt)

answered Jul 12, 2022 at 6:55

A.R.S.

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