SQLAlchemy, Psycopg2 and Postgresql COPY
It looks like Psycopg has a custom command for executing a COPY:
psycopg2 COPY using cursor.copy_from() freezes with large inputs
Is there a way to access this functionality from with SQLAlchemy?
Answer
accepted answer is correct but if you want more than just the EoghanM's comment to go on the following worked for me in COPYing a table out to CSV...
from sqlalchemy import sessionmaker, create_engine
eng = create_engine("postgresql://user:pwd@host:5432/db")
ses = sessionmaker(bind=engine)
dbcopy_f = open('/tmp/some_table_copy.csv','wb')
copy_sql = 'COPY some_table TO STDOUT WITH CSV HEADER'
fake_conn = eng.raw_connection()
fake_cur = fake_conn.cursor()
fake_cur.copy_expert(copy_sql, dbcopy_f)
The sessionmaker isn't necessary but if you're in the habit of creating the engine and the session at the same time to use raw_connection you'll need separate them (unless there is some way to access the engine through the session object that I don't know). The sql string provided to copy_expert is also not the only way to it, there is a basic copy_to function that you can use with subset of the parameters that you could past to a normal COPY TO query. Overall performance of the command seems fast for me, copying out a table of ~20000 rows.
http://initd.org/psycopg/docs/cursor.html#cursor.copy_to http://docs.sqlalchemy.org/en/latest/core/connections.html#sqlalchemy.engine.Engine.raw_connection