[Sqlalchemy-tickets] Issue #4015: Possible Memory Leak on simple operations (zzzeek/sqlalchemy)

[Luca Z. <iss...@bi...>]

New issue 4015: Possible Memory Leak on simple operations
https://bitbucket.org/zzzeek/sqlalchemy/issues/4015/possible-memory-leak-on-simple-operations

Luca Zulian:

I am currently playing around with SQLAlchemy a bit, and I found a strange behaviour about memory usage. I'm using sqlalchemy with version 1.1.10 running on python 2.7.13, macOS Sierra version 10.12.5, MySQL-python 1.2.5, mysql driver version Ver 14.14 Distrib 5.7.18, for osx10.12 (x86_64) using  EditLine wrapper


```
#!python
from contextlib import contextmanager

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

Base = declarative_base()

e = create_engine('mysql://root:root@127.0.0.1:3306/MyDb?charset=utf8')


class Currency(Base):
    __tablename__ = "currency"
    id = Column(Integer, primary_key=True)

Base.metadata.create_all(e)
Session = sessionmaker(autoflush=True, bind=e)


@contextmanager
def session_scope():
    """Provide a transactional scope around a series of operations."""
    session = Session()
    try:
        yield session
        session.commit()
    except:
        session.rollback()
        raise
    finally:
        session.close()


def foo():
    with session_scope() as session2:
        result = session2.query(Currency).filter_by(id=1).first()
        print(result.id)


while True:
    foo()
```
It seems that the memory it's never freed, and that continuously increase.
Also I've got the same problem only opening and closing the session.


```
#!python
from contextlib import contextmanager

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

Base = declarative_base()

e = create_engine('mysql://root:root@127.0.0.1:3306/MyDb?charset=utf8')


class Currency(Base):
    __tablename__ = "currency"
    id = Column(Integer, primary_key=True)

Base.metadata.create_all(e)
Session = sessionmaker(autoflush=True, bind=e)


@contextmanager
def session_scope():
    """Provide a transactional scope around a series of operations."""
    session = Session()
    try:
        yield session
        session.commit()
    except:
        session.rollback()
        raise
    finally:
        session.close()


def foo():
    with session_scope() as session2:
        pass


while True:
    foo()
```