Hi Simon,
Sorry I think I really didn't make what I'm asking for clear.
I have these codes
nodes =
NodesModel.find_by_project_uuid_and_topic_list(project_uuid=project_uuid,
topic_list=node_dict['topics'])
node_id_list = [node.id for node in nodes]
select_sql = text('WITH pn_o AS (SELECT post_id, ARRAY_AGG(DISTINCT
node_id) AS pn_nodes FROM pn GROUP BY post_id), '
'n_o AS (SELECT ARRAY_AGG(DISTINCT node_id) as n_nodes
FROM pn WHERE node_id IN :input_tuple) '
'SELECT post_id FROM pn_o WHERE pn_nodes = (SELECT
n_nodes FROM n_o)')
params = {"input_tuple": tuple(node_id_list)}
results = db.session.execute(select_sql, params).fetchall()
Which does what I want. In the end, in results, I get a list of posts that
have nodes that contain all the topics I need, in other words, the posts
contain all the topic words.
I'm just wondering, if there is a way to ORM the select_sql as I would
prefer to work with the models than the raw SQL. And I'm doing it this way
because I want the server to do the heavy lifting.
Desmond
On 10 Jun 2019, 22:41 +0800, Simon King <si...@simonking.org.uk>, wrote:
I'm still not sure I understand. Here's an example that does what I
*think* you're asking for:
import sqlalchemy as sa
import sqlalchemy.orm as saorm
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
pn = sa.Table(
"pn", Base.metadata,
sa.Column("post_id", sa.Integer, sa.ForeignKey("posts.id")),
sa.Column("node_id", sa.Integer, sa.ForeignKey("nodes.id")),
)
class Node(Base):
__tablename__ = "nodes"
id = sa.Column(sa.Integer, autoincrement=True, primary_key=True)
project_uuid = sa.Column(sa.Text, nullable=False)
topic = sa.Column(sa.Text(20), nullable=False)
posts = saorm.relationship("Post", secondary=pn, backref="nodes")
class Post(Base):
__tablename__ = "posts"
id = sa.Column(sa.Integer, autoincrement=True, primary_key=True)
project_uuid = sa.Column(sa.Text, nullable=False)
if __name__ == "__main__":
engine = sa.create_engine("sqlite://")
Base.metadata.create_all(bind=engine)
Session = saorm.sessionmaker(bind=engine)
projectid = "42a8e275-f153-452b-99d3-645bdd513ca9"
topics = ['a', 'b', 'c', 'd']
nodes = [Node(project_uuid=projectid, topic=t) for t in topics]
posts = [Post(project_uuid=projectid) for i in range(11)]
import random
random.seed(0)
for node in nodes:
node.posts = random.sample(posts, 4)
session = Session()
session.add_all(nodes + posts)
session.flush()
node_ids = [1, 2]
print("Looking for posts with node IDs: %s" % node_ids)
posts = (
session.query(Post)
.join("nodes")
.filter(Node.id.in_(node_ids))
.all()
)
for p in posts:
print("Post %s: Node IDs %s" % (p.id, [n.id for n in p.nodes]))
Simon
On Mon, Jun 10, 2019 at 1:22 PM Desmond Lim <limwen...@gmail.com> wrote:
Hi Simon,
The tables and sample data are below.
So first I search the nodes table for a and b, getting the node_id of them
(in this example, 1 and 2).
Then using the SQL statement, I would get all posts that have 1 and 2 as
the node_id. So in the example data, 100, 103, 108 will be returned as
these posts contain the nodes 1 and 2.
Hope this helps.
Desmond
-------------
CREATE SEQUENCE IF NOT EXISTS nodes_id_seq;
CREATE TABLE "public"."nodes" (
"id" int8 NOT NULL DEFAULT nextval('nodes_id_seq'::regclass),
"project_uuid" uuid NOT NULL,
"topic" varchar(20) NOT NULL,
PRIMARY KEY ("id")
);
CREATE SEQUENCE IF NOT EXISTS posts_id_seq;
CREATE TABLE "public"."posts" (
"id" int8 NOT NULL DEFAULT nextval('posts_id_seq'::regclass),
"project_uuid" uuid NOT NULL,
PRIMARY KEY ("id")
);
CREATE TABLE "public"."pn" (
"post_id" int8 NOT NULL,
"node_id" int8 NOT NULL,
PRIMARY KEY ("post_id","node_id")
);
INSERT INTO "public"."nodes" ("id", "project_uuid", "topic", "size",
"given_id") VALUES
('1', '42a8e275-f153-452b-99d3-645bdd513ca9', 'a'),
('2', '42a8e275-f153-452b-99d3-645bdd513ca9', 'b'),
('3', '42a8e275-f153-452b-99d3-645bdd513ca9', 'c'),
('4', '42a8e275-f153-452b-99d3-645bdd513ca9', 'd')
INSERT INTO "public"."posts" ("id", "project_uuid") VALUES
('100', '42a8e275-f153-452b-99d3-645bdd513ca9'),
('101', '42a8e275-f153-452b-99d3-645bdd513ca9'),
('102', '42a8e275-f153-452b-99d3-645bdd513ca9'),
('103', '42a8e275-f153-452b-99d3-645bdd513ca9'),
('104', '42a8e275-f153-452b-99d3-645bdd513ca9'),
('105', '42a8e275-f153-452b-99d3-645bdd513ca9'),
('106', '42a8e275-f153-452b-99d3-645bdd513ca9'),
('107', '42a8e275-f153-452b-99d3-645bdd513ca9'),
('108', '42a8e275-f153-452b-99d3-645bdd513ca9'),
('109', '42a8e275-f153-452b-99d3-645bdd513ca9'),
('110', '42a8e275-f153-452b-99d3-645bdd513ca9')
INSERT INTO "public"."pn" ("post_id", "node_id") VALUES
('1', '100'),
('2', '100'),
('3', '100'),
('2', '101'),
('3', '101'),
('4', '101'),
('5', '101'),
('3', '102'),
('4', '102'),
('1', '103'),
('2', '103'),
('3', '103'),
('2', '104'),
('4', '104'),
('1', '105'),
('4', '105'),
('3', '105'),
('3', '106'),
('4', '106'),
('4', '107'),
('1', '108'),
('2', '108'),
('3', '109'),
('1', '109'),
('4', '109'),
('2', '110'),
('3', '110')
ALTER TABLE "public"."posts" ADD FOREIGN KEY ("project_uuid") REFERENCES
"public"."projects"("uuid");
ALTER TABLE "public"."pn" ADD FOREIGN KEY ("post_id") REFERENCES
"public"."posts"("id");
ALTER TABLE "public"."pn" ADD FOREIGN KEY ("node_id") REFERENCES
"public"."nodes"("id");
On Mon, 10 Jun 2019 at 17:08, Simon King <si...@simonking.org.uk> wrote:
Hi Desmond.
I don't really understand your table structure. Could you present it
in the form of a standalone script that we can run (including sample
data)?
Thanks,
Simon
On Mon, Jun 10, 2019 at 2:57 AM Desmond Lim <limwen...@gmail.com> wrote:
Hi there,
I really have no idea how to do this via sqlalchemy. I have 2 tables:
class NodesModel(db.Model):
__tablename__ = 'nodes'
id = db.Column(db.BigInteger, primary_key=True)
topic = db.Column(db.String(20), nullable=False)
pn = relationship("PNModel", backref="nodes")
class PNModel(db.Model):
__tablename__ = 'pn'
post_id = db.Column(db.BigInteger, db.ForeignKey('posts.id'),
primary_key=True)
node_id = db.Column(db.BigInteger, db.ForeignKey('nodes.id'),
primary_key=True)
I will get a list of nodes that have the topic (e.g. one, two). Then taking
the nodes, I'll select the PN that have both nodes (it can be 1 or more)
associated with it.
e.g.
I'm doing it this way at this point:
nodes = NodesModel.find_by_topic_list(topic_list)
node_id_list = [node.id for node in nodes]
Then running this sql statement:
WITH pn_1 AS (SELECT post_id, ARRAY_AGG(DISTINCT node_id) AS nodes
FROM pn GROUP BY post_id),
nodes_1 AS (SELECT ARRAY_AGG(DISTINCT id) AS s_nodes
FROM pn WHERE node_id IN (dict(node_id_list))
SELECT DISTINCT post_id FROM pn_1
WHERE nodes_1 = (SELECT s_nodes FROM select_nodes);
There has to be a better and more elegant way to do this with SQLAlchemy
and I can't seem to figure it out. I've tried using subqueries and then I
realised that I'm actually calling the nodes table twice, which I shouldn't
have to.
Can anyone tell me how to use the nodes table to get the post_id form pn
(after which getting the post should be easy via ORM should be easy, I
think).
Thanks.
Desmond
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