如何从 sqlalchemy 中的 jsonb 列的嵌套列表中返回特定的字典键

Question

I am attempting to return some named columns from a jsonb data set that is stored with PostgreSQL.

I am able to run a raw query that meets my needs directly, however I am trying to run the query utilising SQLAlchemy, in order to ensure that my code is 'pythonic' and easy to read.

The query that returns the correct result (two columns) is:

SELECT  
    tmp.item->>'id',
    tmp.item->>'name'
FROM (SELECT jsonb_array_elements(t.data -> 'users') AS item FROM tpeople t) as tmp

Example json (each user has 20+ columns)

{ "results":247, "users": [
{"id":"202","regdate":"2015-12-01","name":"Bob Testing"},
{"id":"87","regdate":"2014-12-12","name":"Sally Testing"},
{"id":"811", etc etc}
...
]}

The table is simple enough, with a PK, datetime of json extraction, and the jsonb column for the extract

CREATE TABLE tpeople
(
    record_id bigint NOT NULL DEFAULT nextval('"tpeople_record_id_seq"'::regclass) ( INCREMENT 1 START 1 MINVALUE 1 MAXVALUE 9223372036854775807 CACHE 1 ),
    scrape_time timestamp without time zone NOT NULL,
    data jsonb NOT NULL,
    CONSTRAINT "tpeople_pkey" PRIMARY KEY (record_id)
);

Additionally I have a People Class that looks as follows:

class people(Base):
    __tablename__ = 'tpeople'

    record_id = Column(BigInteger, primary_key=True, server_default=text("nextval('\"tpeople_record_id_seq\"'::regclass)"))
    scrape_time = Column(DateTime, nullable=False)
    data = Column(JSONB(astext_type=Text()), nullable=False)

Presently my code to return the two columns looks like this:

from db.db_conn import get_session // Generic connector for my db
from model.models import people
from sqlalchemy import func,

sess = get_session()

sub = sess.query(func.jsonb_array_elements(people.data["users"]).label("item")).subquery()
test = sess.query(sub.c.item).select_entity_from(sub).all()

SQLAlchemy generates the following SQL:

SELECT anon_1.item AS anon_1_item 
FROM (SELECT jsonb_array_elements(tpeople.data -> %(data_1)s) AS item 
FROM tpeople) AS anon_1
{'data_1': 'users'}

But nothing I seem to do can allow me to only get certain columns within the item itself like the raw SQL I can write. Some of the approaches I have tried as follows (they all error out):

test = sess.query("sub.item.id").select_entity_from(sub).all()

test = sess.query(sub.item.["id"]).select_entity_from(sub).all()

aas = func.jsonb_to_recordset(people.data["users"])
res = sess.query("id").select_from(aas).all()

sub = select(func.jsonb_array_elements(people.data["users"]).label("item"))

Presently I can extract the columns I need in a simple for loop, but this seems like a hacky way to do it, and I'm sure there is something dead obvious I'm missing.

for row in test:
    print(row.item['id'])

Answer 1

Searched for a few hours eventually found some who accidentally did this while trying to get another result.

sub = sess.query(func.jsonb_array_elements(people.data["users"]).label("item")).subquery()
tmp = sub.c.item.op('->>')('id')
tmp2 = sub.c.item.op('->>')('name')
test = sess.query(tmp, tmp2).all()