CODEWITHSUNDEEP
pythonpostgresqlsqlalchemy
skyler
skyler

Reputation: 8338

Update a PostgreSQL array using SQLAlchemy

I'm trying to update an integer array on a PostgreSQL table using a SQL statement in SQLAlchemy Core. I first tried using the query generator, but couldn't figure out how to do that either. I believe that Psycopg2, which is the dialect that I'm using, can automatically form the array into a format that PostgreSQL can accept.

Here's the table schema:

CREATE TABLE surveys (
    survey_id serial PRIMARY KEY,
    question_ids_ordered INTEGER[],
    created_at TIMESTAMP NOT NULL DEFAULT now(),
);

And the SQLAlchemy statement:

survey_id = 46
question_ids_ordered = [237, 238, 239, 240, 241, 242, 243]

with engine.begin() as conn:
    conn.execute("""UPDATE surveys
                    SET question_ids_ordered = %s
                    WHERE survey_id = %s""",
                    question_ids_ordered, survey_id)

And the traceback I receive is:

Traceback (most recent call last):
  File "foo.py", line 16, in <module>
    res = add_question_to_group(current_user, 46, 358, question_ids_ordered, new_group_name="Jellyfish?")
  File "/vagrant/workspace/panel/panel/survey.py", line 80, in add_question_to_group
    question_ids_ordered, survey_id)
  File "/home/vagrant/.virtualenvs/project/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 664, in execute
    params)
  File "/home/vagrant/.virtualenvs/project/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 808, in _execute_text
    statement, parameters
  File "/home/vagrant/.virtualenvs/project/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 831, in _execute_context
    None, None)
  File "/home/vagrant/.virtualenvs/project/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 827, in _execute_context
    context = constructor(dialect, self, conn, *args)
  File "/home/vagrant/.virtualenvs/project/lib/python2.6/site-packages/sqlalchemy/engine/default.py", line 513, in _init_statement
    for p in parameters]
sqlalchemy.exc.StatementError: 'int' object is not iterable (original cause: TypeError: 'int' object is not iterable) 'UPDATE surveys\n                        SET question_ids_ordered = %s\n                        WHERE survey_id = %s' ([237, 238, 239, 240, 241, 242, 243], 46)

What am I doing wrong?

Upvotes: 17

Views: 33071

Answers (2)

Lucian
Lucian

Reputation: 894

In Flask, the model of your Survey table will look something like this:

class Survey(UserMixin, db.Model):
    __tablename__ = 'surveys'
    id = db.Column(db.Integer, primary_key=True)
    question_ids_ordered = db.Column('question_ids_ordered', db.ARRAY(db.Integer))

And you want to update the question_ids_ordered field, you can use ORM like so:

from sqlalchemy.orm.attributes import flag_modified

survery = (Survey
           .query
           .filter(Survey.id == 46)).first()

survery.question_ids_ordered.remove(237)
flag_modified(survery, "question_ids_ordered")
db.session.merge(survery)
db.session.flush()
db.session.commit()

Upvotes: 1

Audrius Kažukauskas
Audrius Kažukauskas

Reputation: 13533

If your table is defined like this:

from datetime import datetime
from sqlalchemy import *
from sqlalchemy.dialects.postgresql import ARRAY

meta = MetaData()
surveys_table = Table('surveys', meta,
    Column('surveys_id', Integer, primary_key=True),
    Column('questions_ids_ordered', ARRAY(Integer)),
    Column('created_at', DateTime, nullable=False, default=datetime.utcnow)
)

Then you can simply update your array in the following way (works with psycopg2):

engine = create_engine('postgresql://localhost')
conn = engine.connect()
u = surveys_table.update().where(surveys_table.c.id == 46).\
     values(questions_ids_ordered=[237, 238, 239, 240, 241, 242, 243])
conn.execute(u)
conn.close()

Or, if you prefer, write raw SQL using text() construct:

from sqlalchemy.sql import text
with engine.connect() as conn:
    u = text('UPDATE surveys SET questions_ids_ordered = :q WHERE id = :id')
    conn.execute(u, q=[237, 238, 239, 240, 241, 242, 243], id=46)

Upvotes: 23

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