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How to insert values into a postgresql database with serial id using sqlalchemy

I have a function that I use to update tables in PostgreSQL. It works great to avoid duplicate insertions by creating a temp table and dropping it upon completion. However, I have a few tables with serial ids and I have to pass the serial id in a column. Otherwise, I get an error that the keys are missing. How can I insert values in those tables and have the serial key get assigned automatically? I would prefer to modify the function below if possible.
def export_to_sql(df, table_name):
from sqlalchemy import create_engine
engine = create_engine(f'postgresql://{user}:{password}#{host}:5432/{user}')
df.to_sql(con=engine,
name='temporary_table',
if_exists='append',
index=False,
method = 'multi')
with engine.begin() as cnx:
insert_sql = f'INSERT INTO {table_name} (SELECT * FROM temporary_table) ON CONFLICT DO NOTHING; DROP TABLE temporary_table'
cnx.execute(insert_sql)
code used to create the tables
CREATE TABLE symbols
(
symbol_id serial NOT NULL,
symbol varchar(50) NOT NULL,
CONSTRAINT PK_symbols PRIMARY KEY ( symbol_id )
);
CREATE TABLE tweet_symols(
tweet_id varchar(50) REFERENCES tweets,
symbol_id int REFERENCES symbols,
PRIMARY KEY (tweet_id, symbol_id),
UNIQUE (tweet_id, symbol_id)
);
CREATE TABLE hashtags
(
hashtag_id serial NOT NULL,
hashtag varchar(140) NOT NULL,
CONSTRAINT PK_hashtags PRIMARY KEY ( hashtag_id )
);
CREATE TABLE tweet_hashtags
(
tweet_id varchar(50) NOT NULL,
hashtag_id integer NOT NULL,
CONSTRAINT FK_344 FOREIGN KEY ( tweet_id ) REFERENCES tweets ( tweet_id )
);
CREATE INDEX fkIdx_345 ON tweet_hashtags
(
tweet_id
);

The INSERT statement does not define the target columns, so Postgresql will attempt to insert values into a column that was defined as SERIAL.
We can work around this by providing a list of target columns, omitting the serial types. To do this we use SQLAlchemy to fetch the metadata of the table that we are inserting into from the database, then make a list of target columns. SQLAlchemy doesn't tell us if a column was created using SERIAL, but we will assume that it is if it is a primary key and is set to autoincrement. Primary key columns defined with GENERATED ... AS IDENTITY will also be filtered out - this is probably desirable as they behave in the same way as SERIAL columns.
import sqlalchemy as sa
def export_to_sql(df, table_name):
engine = sa.create_engine(f'postgresql://{user}:{password}#{host}:5432/{user}')
df.to_sql(con=engine,
name='temporary_table',
if_exists='append',
index=False,
method='multi')
# Fetch table metadata from the database
table = sa.Table(table_name, sa.MetaData(), autoload_with=engine)
# Get the names of columns to be inserted,
# assuming auto-incrementing PKs are serial types
column_names = ','.join(
[f'"{c.name}"' for c in table.columns
if not (c.primary_key and c.autoincrement)]
)
with engine.begin() as cnx:
insert_sql = sa.text(
f'INSERT INTO {table_name} ({column_names}) (SELECT * FROM temporary_table) ON CONFLICT DO NOTHING; DROP TABLE temporary_table'
)
cnx.execute(insert_sql)

Create table in specific tablespace with SQLalchemy

I can create new table in tablespace using raw query:
engine = sqlalchemy.engine.create_engine(ENGINE_PATH_DDS, encoding="utf-8")
connection = engine.connect()
conn = engine.raw_connection()
cur = conn.cursor()
sql = """
CREATE TABLE {schema}.{table_name}
(
ID NUMBER GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
STATUS NVARCHAR2(32) NOT NULL,
DESCR NVARCHAR2(256) DEFAULT NULL
)
TABLESPACE SOME_TABLESPACE
""".format(table_name = table_name, schema = SCHEMA)
cur.execute(sql)
Created table is accesseble for all users with privileges. But how to do same thing without raw_connection? With this approach:
metadata = MetaData(engine)
table = Table('Example',metadata,
Column('id',Integer, primary_key=True),
Column('status',String))
metadata.create_all()
How to specify tablespase for new table?
Such code works:
df = pd.DataFrame(columns=['id', 'status', 'descr']) # pandas data frame
df.to_sql(con=connection, name=tbl, schema=SCHEMA, index=False, dtype=data_types, if_exists='replace')
but when tring to insert any data i got:
ORA-01950: no privileges on tablespace 'USERS'

Why am I getting a "relation does not exist" error for existing table with sqlalchemy Metadata?

I have the following code which throws the following error
engine = create_engine('postgresql+psycopg2:....', convert_unicode=True)
metadata = sqlalchemy.MetaData()
table = sqlalchemy.Table('omni.all_order', metadata,
sqlalchemy.Column('o_id', sqlalchemy.Integer),
sqlalchemy.Column('order', sqlalchemy.String),
)
ins = table.insert().values(all_rows)
engine.execute(ins)
sqlalchemy.exc.ProgrammingError: (psycopg2.ProgrammingError) relation
"omni.all_order" does not exist
But the following two codes work fine
engine = create_engine('postgresql+psycopg2:....', convert_unicode=True)
result = engine.execute("SELECT * from omni.all_order ")
rows = result.fetchall()
print(rows)
--
engine = create_engine('postgresql+psycopg2:....', convert_unicode=True)
engine.execute("INSERT INTO omni.all_order (o_id) VALUES (1) ")
Creating another table first in the same schema (omni) throws the same error
engine = create_engine('postgresql+psycopg2:....', convert_unicode=True)
result = engine.execute("CREATE TABLE omni.all_order_s(o_id INT, order VARCHAR(80))")
metadata = sqlalchemy.MetaData()
table = sqlalchemy.Table('omni.all_order_s', metadata,
sqlalchemy.Column('o_id', sqlalchemy.Integer),
sqlalchemy.Column('order', sqlalchemy.String),
)
ins = table.insert().values(all_rows)
engine.execute(ins)
sqlalchemy.exc.ProgrammingError: (psycopg2.ProgrammingError) relation
"omni.all_order_s" does not exist
but creating it outside of the schema works fine
engine = create_engine('postgresql+psycopg2:....', convert_unicode=True)
result = engine.execute("CREATE TABLE all_order_s(o_id INT, order VARCHAR(80))")
metadata = sqlalchemy.MetaData()
table = sqlalchemy.Table('all_order_s', metadata,
sqlalchemy.Column('o_id', sqlalchemy.Integer),
sqlalchemy.Column('order', sqlalchemy.String),
)
ins = table.insert().values(all_rows)
engine.execute(ins)
Any ideas why this is?

Pass the table's schema using the schema= keyword argument instead of including it in the table's name:
table = sqlalchemy.Table('all_order', metadata,
sqlalchemy.Column('o_id', sqlalchemy.Integer),
sqlalchemy.Column('order', sqlalchemy.String),
schema='omni',
)
Currently it is quoted as a whole.

I had the same problem and I found the solution in this link: https://dba.stackexchange.com/questions/192897/postgres-relation-does-not-exist-error.
When you create the table name from a variable, the name is passed with quotes, so the name is case sensitive and need the quotes when you called again.

Sqlalchemy - Auto-instantiate all tables

Here a simple sqlalchemy task, where i try to create instances of each table present in the database:
from sqlalchemy import MetaData, create_engine, Table
engine = create_engine("here my engine details...")
metadata = MetaData()
If i type engine.table_names() , I can see all my tables' names, for instance ['indicators', 'prices', 'scripts'].
I would normally go at creating instances of each of them as follow:
scripts = Table('scripts', metadata, autoload = True, autoload_with=engine)
indicators = Table('indicators', metadata, autoload = True, autoload_with=engine)
prices = Table('prices', metadata, autoload = True, autoload_with=engine)
But is there a way to create the Table instances without coding them explicitely?
Doing this:
tables = engine.table_names()
for table in tables:
table = Table( table , metadata, autoload = True, autoload_with=engine)
obviously doesn't work.
Any suggestion appreciated

You can do just that. This code will get you a list of tables:
my_tables = [Table(table,metadata,autoload=True,autoload_with=engine) for
table in engine.table_names()]
If you prefer a dictionary do this:
my_tables = {table:Table(table,metadata,autoload=True,autoload_with=engine)
for table in engine.table_names()}
With the dictionary you get O(1) lookup of tables when accessing the elements of your dictionary:
my_tables['indicators']

How to specify the primary id when inserting rows with sqlalchemy when id dos not have autoincrement?

I do have database table that has an id primary key that is not an auto-increment (sequence). So it's up to the user to create an unique id or the insert will fail.
This table is not under my control, so I cannot change the database structure.
from sqlalchemy import create_engine, Table, MetaData
import psycopg2
db = create_engine('postgresql://...', echo=False).connect()
meta = MetaData()
meta.reflect(bind=db)
t = Table("mytable", meta, autoload=True, autoload_with=db)
values = { "title":"title", "id": ... }# ???
t.insert(bind=db, values=values).execute()

Given this is "single-user" / "single-client" system, you should be able to use the Column defaults: Python-Executed Functions. The example on the documentation linked to is enough to get you started. I would, however, use python function but with proper initialization from the datatabase adn still stored in a global variable:
def new_id_factory():
if not('_MYTABLE_ID_' in globals()):
q = db.execute("select max(mytable.id) as max_id from mytable").fetchone()
_MYTABLE_ID_ = (q and q.max_id) or 0
_MYTABLE_ID_ += 1
return _MYTABLE_ID_
t = Table("mytable", Base.metadata,
Column('id', Integer, primary_key=True, default=new_id_factory), #
autoload=True, autoload_with=db,
)