Now many developers (not all) have a tendency to use a number of technologies, not understanding how they work and which problems they solve and which ones they create. The talk will be devoted to a review of libraries in Python, which help us work with databases, namely, effectively receive data. I will try to tell and answer the following questions: why is it sometimes worth writing RAW SQL; when it is worth paying attention to ORM, in particular, their advantages and differences; where and how ORM will be slower, and where there will be no difference; how and what ORMs can work in asynchronous mode; what does GraphQL have to do with it and how can it help.

1. ORM vs GraphQL
Oleksandr Tarasenko
EVO.company / prom.ua

2. Agenda
● Raw SQL in python
● Python ORM libs
● async/await and ORM solutions
● GraphQL implementation
2

3. WHY?
3

4. 4

5. 5

6. 6
GraphQL

7. Raw SQL in python
import psycopg2
class pg_conn:
def __enter__(self):
self.conn = psycopg2.connect(
dbname='fwdays', user='highload'
)
return self.conn
def __exit__(self, exc_type, exc_val, exc_tb):
if hasattr(self, 'conn'):
self.conn.close()
7
with pg_conn() as db:
cur = db.cursor()
query = "insert into product('name') values('toy')"
cur.execute(query)
db.commit()
cur.close()
db.close()

8. Raw SQL in python
● psycopg2
● written in C
● implementation of the DB API 2.0 (PEP 249)
● works like a libpq wrapper
8

9. Raw SQL in python
● psycopg2
● written in C
● implementation of the DB API 2.0 (PEP 249)
● works like a libpq wrapper
9

10. Raw SQL in python
import psycopg2
class pg_conn:
def __enter__(self):
self.conn = psycopg2.connect(
dbname='fwdays', user='highload'
)
return self.conn
def __exit__(self, exc_type, exc_val, exc_tb):
if hasattr(self, 'conn'):
self.conn.close()
10
with pg_conn() as db:
cur = db.cursor()
query = "insert into product('name') values('toy')"
cur.execute(query)
db.commit()
cur.close()
db.close()

11. Raw SQL in python
insert into products('name') values('toy');
11

12. Raw SQL in python
insert into products('name') values('toy');
select settings from application_settings
where company_id in (
3244414, 3239428, 3246756, 3215974
);
12

13. Raw SQL in python
13
select csa.company_id, count(csa.id)
from company_site_attributes as csa
join company as c on c.id = csa.company_id
join site_filters as csf on csf.attribute_id = csa.id
where portal_attribute_id in (1536, 17536) and
c.premium_service_id > 0 and
csa.status = 0 and
csf.status = 0
group by csa.company_id, csa.id
having count(csa.id) > 1;

14. Raw SQL in python
14
select csa.company_id, count(csa.id)
from company_site_attributes as csa
join company as c on c.id = csa.company_id
join site_filters as csf on csf.attribute_id = csa.id
where portal_attribute_id in (1536, 17536) and
c.premium_service_id > 0 and
csa.status = 0 and
csf.status = 0
group by csa.company_id, csa.id
having count(csa.id) > 1;

15. Raw SQL
● small tables
15

16. Raw SQL
● small tables
● few tables
16

17. Raw SQL
● small tables
● few tables
● no complicated types
17

18. Raw SQL
● small tables
● few tables
● no complicated types
● no need to manage scheme in the app
18

19. Raw SQL
● small tables
● few tables
● no complicated types
● no need to manage scheme in the app
● no migrations
19

20. Raw SQL
● small tables
● few tables
● no complicated types
● no need to manage scheme in the app
● no migrations
● no dynamic queries
20

21. Raw SQL
● small tables
● few tables
● no complicated types
● no need to manage scheme in the app
● no migrations
● no dynamic queries
● no app session managing
● ...
21

22. Python ORM
22

23. Python ORM
● SQLAlchemy
● Django ORM
● Peewee
● Pony ORM
● Tortoise ORM
● SQLObject
● GINO *
● ...
23

24. Python ORM +
● Scalability
● Security
● Trust
● Time
24

25. Python ORM -
● Speed
● Scope
25

27. SQLAlchemy
● SQLAlchemy Core
● SQLAlchemy ORM
27

28. 28

29. 29

30. 30

31. 31

32. 32

35. SQLAlchemy -> asyncio
● psycopg ?

36. SQLAlchemy -> asyncio
● psycopg ?

37. AsyncIO vs SQLAlchemy
https://techspot.zzzeek.org/2015/02/15/asynchronous-python-and-databases/

38. SQLAlchemy -> asyncio
● psycopg
● aiopg
● asyncpg

39. aiopg vs asyncpg
https://www.youtube.com/watch?v=bY6ZU0-26TA

40. aiopg
psycopg
libpq
pgbouncer
postgres
asyncpg
pgbouncer
postgres

41. 41
GraphQL

42. GraphQL in Python
● Graphene
● Ariadne
● Strawberry
● Hiku

43. Graphene
from graphene import ObjectType, String, Schema
class Query(ObjectType):
name = String(description='Name field')
formated_price = String(description='Price field')
def resolve_name(self, info):
name = get_product_name()
...
return name
def resolve_price(self, info):
price = get_product_price()
...
return format_price(price)
schema = Schema(query=Query)
query = '''
query Products {
name
price
}
'''
result = schema.execute(query)

44. Graphene
Base = declarative_base()
Base.query = db_session.query_property()
class ProductModel(Base):
__tablename__ = 'product'
id = Column(Integer, primary_key=True)
name = Column(String)
price = Column(Integer)
class Product(SQLAlchemyObjectType):
class Meta:
model = ProductModel
interfaces = (relay.Node, )
class Query(ObjectType):
node = relay.Node.Field()
products = SQLAlchemyConnectionField(Product)
schema = Schema(query=Query, types=[Product, ])

45. Graphene
query = '''
{
products {
edges {
node {
name
price
}
}
}
}
'''

46. Ariadne
from ariadne import ObjectType, QueryType, gql,
make_executable_schema
from ariadne.asgi import GraphQL
type_defs = gql("""
type Query {
products: [Product!]!
}
type Product {
id: Int
name: String
price: Int
}
""")
query = QueryType()
@query.field("products")
def resolve_products(*_):
...
return get_products_from_db()
product = ObjectType("Product")
@product.field("name")
def resolve_product_name(product, *_):
...
return get_product_name_from_db()
schema = make_executable_schema(type_defs, query,
product)
app = GraphQL(schema, debug=True)

47. Ariadne with ORM
https://github.com/mirumee/ariadne/issues/115

48. Hiku
from hiku.graph import Graph, Node, Link, Field, ...
from hiku.sources import sqlalchemy as sa
from hiku.types import Boolean, Integer, String, TypeRef, ...
product_query = sa.FieldsQuery('db.session', Product.table)
# product_query = asyncsa.FieldsQuery('db.session_async', Product.table)
low_level_graph = Graph([
Node('Product', [
Field('id', Integer, product_query),
Field('name', String, product_query),
Field('price', None, product_query),
...
])
query = '''
product(ids: [1234, 1235]) {
id
name
price
}
'''
"""
SELECT id, name, price FROM product
WHERE id IN (:id1, :id2, ..., :idN)
"""

49. Hiku
low_level_graph = Graph([
Node('Product', [
Field('id', Integer, product_query),
...
Link(
'discount',
Optional[TypeRef['Discount']],
product_to_discount_query,
requires='id',
),
]),
Node('Discount', [
Field('id', Integer, discount_query),
Field('amount', Integer, discount_query),
])
])
discount_query = sa.FieldsQuery('db.session', Discount.__table__)
"""
SELECT id, name, price, price_currency_id FROM product
WHERE id IN (:id1, :id2, ..., :idN)
"""
product_to_discount_query = sa.LinkQuery(
'db.session',
from_column=Discount.product_id,
to_column=Discount.product_id,
)
"""
SELECT product_id FROM discount
WHERE product_id IN (:id1, :id2, ..., :idN)
"""

50. Hiku
product_sg = SubGraph(low_level_graph, 'Product')
high_level_graph = Graph([
Node('Product', [
Field('id', String, product_sg),
Field('name', String, product_sg.compile(S.this.name)),
Field('priceText', String, product_sg.compile(
get_price_text(S.this)
)),
Field('hasDiscount', Boolean, product_sg.compile(
is_discount_available(S.this, S.this.discount)
)),
Field('discountedText', String, product_sg.compile(
get_discounted_text(S.this, S.this.discount)
)),
]),
])
@define(Record[{
'price': Float,
'price_currency_id': Integer,
'currency_settings': Any
}])
def get_price_text(product):
product_price_text = format_currency_data(
product_price,
product['price_currency_id'],
)
...
return product_price_text.formatted_number

51. ORM vs GraphQL

52. GraphQL -> EdgeDB

53. GraphQL -> EdgeDB
CREATE DATABASE fwdays;
START TRANSACTION;
CREATE MIGRATION catalog TO {
type Product {
required property name -> str;
property price -> int64;
required link discount -> Discount;
}
type Discount {
required property amount -> int64;
}
};
COMMIT MIGRATION movies;
COMMIT;
INSERT Product {
name := 'random name',
price := 100,
discount := (
INSERT Discount {
amount := 10,
}
)
};
INSERT Product {
name := 'another random name',
price := 200,
discount := (
SELECT Discount
FILTER
.action_id = 1234
LIMIT 1
)
};

54. GraphQL -> EdgeDB
SELECT Product;
SELECT Product {
name,
price
};
SELECT Product {
name,
price,
discount: {
amount
}
}
FILTER .name ILIKE '%random%';
{
Product {
name
price
}
}
{
Product(filter: {name: {eq: "random"}}) {
name
price
discount {
amount
}
}
}

55. ORM vs GraphQL

56. thnx