SQlAlchemy bulk insert is taking too much time for postgresql connection string

While using the bulk insertion code as given in the performance link in SQLAlchemy http://docs.sqlalchemy.org/en/latest/faq/performance.html , the sqlite works fine and takes time as described in their document. While using the same code for the postgresql connection string . The total time is multiplied by many times.

Is there any way to make it faster in postgresql? What i am doing wrong here ??

Especially bulk_insert_mappings and bulk_save_objects, which are my only options to insert 370,000 rows.

Postgresql connection string

connection_string = 'postgresql://' + conf.DB_USER + ':' + conf.DB_PASSWORD + '@' + \
                    conf.DB_HOST + ':' + conf.DB_PORT + '/' + conf.DB_NAME

Code used for checking performance :

import time
import sqlite3

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String,  create_engine
from sqlalchemy.orm import scoped_session, sessionmaker


Base = declarative_base()
DBSession = scoped_session(sessionmaker())
engine = None


class Customer(Base):
    __tablename__ = "customer"
    id = Column(Integer, primary_key=True)
    name = Column(String(255))


def init_sqlalchemy(dbname='sqlite:///sqlalchemy.db'):
    global engine
    connection_string = 'postgresql://' + 'scott' + ':' + 'tiger' + '@' + \
                        'localhost' + ':' + '5432' + '/' + 'test_db'
    engine = create_engine(connection_string, echo=False)
    DBSession.remove()
    DBSession.configure(bind=engine, autoflush=False, expire_on_commit=False)
    Base.metadata.drop_all(engine)
    Base.metadata.create_all(engine)


def test_sqlalchemy_orm(n=100000):
    init_sqlalchemy()
    t0 = time.time()
    for i in xrange(n):
        customer = Customer()
        customer.name = 'NAME ' + str(i)
        DBSession.add(customer)
        if i % 1000 == 0:
            DBSession.flush()
    DBSession.commit()
    print(
        "SQLAlchemy ORM: Total time for " + str(n) +
        " records " + str(time.time() - t0) + " secs")


def test_sqlalchemy_orm_pk_given(n=100000):
    init_sqlalchemy()
    t0 = time.time()
    for i in xrange(n):
        customer = Customer(id=i+1, name="NAME " + str(i))
        DBSession.add(customer)
        if i % 1000 == 0:
            DBSession.flush()
    DBSession.commit()
    print(
        "SQLAlchemy ORM pk given: Total time for " + str(n) +
        " records " + str(time.time() - t0) + " secs")


def test_sqlalchemy_orm_bulk_save_objects(n=100000):
    init_sqlalchemy()
    t0 = time.time()
    n1 = n
    while n1 > 0:
        n1 = n1 - 10000
        DBSession.bulk_save_objects(
            [
                Customer(name="NAME " + str(i))
                for i in xrange(min(10000, n1))
            ]
        )
    DBSession.commit()
    print(
        "SQLAlchemy ORM bulk_save_objects(): Total time for " + str(n) +
        " records " + str(time.time() - t0) + " secs")

def test_sqlalchemy_orm_bulk_insert(n=100000):
    init_sqlalchemy()
    t0 = time.time()
    n1 = n
    while n1 > 0:
        n1 = n1 - 10000
        DBSession.bulk_insert_mappings(
            Customer,
            [
                dict(name="NAME " + str(i))
                for i in xrange(min(10000, n1))
            ]
        )
    DBSession.commit()
    print(
        "SQLAlchemy ORM bulk_insert_mappings(): Total time for " + str(n) +
        " records " + str(time.time() - t0) + " secs")

def test_sqlalchemy_core(n=100000):
    init_sqlalchemy()
    t0 = time.time()
    engine.execute(
        Customer.__table__.insert(),
        [{"name": 'NAME ' + str(i)} for i in xrange(n)]
    )
    print(
        "SQLAlchemy Core: Total time for " + str(n) +
        " records " + str(time.time() - t0) + " secs")


def init_sqlite3(dbname):
    conn = sqlite3.connect(dbname)
    c = conn.cursor()
    c.execute("DROP TABLE IF EXISTS customer")
    c.execute(
        "CREATE TABLE customer (id INTEGER NOT NULL, "
        "name VARCHAR(255), PRIMARY KEY(id))")
    conn.commit()
    return conn


def test_sqlite3(n=100000, dbname='sqlite3.db'):
    conn = init_sqlite3(dbname)
    c = conn.cursor()
    t0 = time.time()
    for i in xrange(n):
        row = ('NAME ' + str(i),)
        c.execute("INSERT INTO customer (name) VALUES (?)", row)
    conn.commit()
    print(
        "sqlite3: Total time for " + str(n) +
        " records " + str(time.time() - t0) + " sec")

if __name__ == '__main__':
    test_sqlalchemy_orm(100000)
    test_sqlalchemy_orm_pk_given(100000)
    test_sqlalchemy_orm_bulk_save_objects(100000)
    test_sqlalchemy_orm_bulk_insert(100000)
    test_sqlalchemy_core(100000)
    test_sqlite3(100000)

Output :

SQLAlchemy ORM: Total time for 100000 records 40.6781959534 secs
SQLAlchemy ORM pk given: Total time for 100000 records 21.0855250359 secs
SQLAlchemy ORM bulk_save_objects(): Total time for 100000 records 14.068707943 secs
SQLAlchemy ORM bulk_insert_mappings(): Total time for 100000 records 11.6551070213 secs
SQLAlchemy Core: Total time for 100000 records 12.5298728943 secs
sqlite3: Total time for 100000 records 0.477468013763 sec

Using the original connection string (i.e. sqlite):

engine = create_engine(dbname, echo=False)

Output :

SQLAlchemy ORM: Total time for 100000 records 16.9145789146 secs
SQLAlchemy ORM pk given: Total time for 100000 records 10.2713520527 secs
SQLAlchemy ORM bulk_save_objects(): Total time for 100000 records 3.69206118584 secs
SQLAlchemy ORM bulk_insert_mappings(): Total time for 100000 records 1.00701212883 secs
SQLAlchemy Core: Total time for 100000 records 0.467703104019 secs
sqlite3: Total time for 100000 records 0.566409826279 sec