remove side effect when import flickrhistory

src/flickrhistory/__init__.py

@@ -15,4 +15,4 @@
 except ImportError:
     pass
 
-__version__ = "0.3.0.dev0"
+__version__ = "0.3.0.dev1"

src/flickrhistory/database/__init__.py

@@ -13,7 +13,7 @@
     "UserSaver",
 ]
 
-from .engine import Session
 from .models import License, Photo, User
 from .photo_saver import PhotoSaver
+from .session import Session
 from .user_saver import UserSaver

src/flickrhistory/database/databaseschemaupdater.py

@@ -12,7 +12,7 @@
 
 import sqlalchemy
 
-from .engine import engine
+from ..config import Config
 
 
 # for now, schema updates are SQL only and work on PostgreSQL, only.
@@ -48,7 +48,9 @@ class DatabaseSchemaUpdater:
     def __init__(self):
         """Update the database schema if necessary."""
         # Try to create database table for schema version
-        with engine.begin() as connection:
+        with Config() as config:
+            self.engine = sqlalchemy.create_engine(config["database_connection_string"])
+        with self.engine.begin() as connection:
             connection.execute(
                 sqlalchemy.text(
                     """
@@ -65,7 +67,7 @@ def __init__(self):
     @property
     def installed_version(self):
         """Return current version."""
-        with engine.connect() as connection:
+        with self.engine.connect() as connection:
             installed_version = connection.execute(
                 sqlalchemy.text(
                     """
@@ -92,18 +94,17 @@ def update_to_latest(self):
                 file=sys.stderr,
                 flush=True,  # so that we don’t seem without work
             )
-            with engine.begin() as connection:
+            with self.engine.connect() as connection:
                 next_version = self.installed_version + 1
                 connection.execute(sqlalchemy.text(SCHEMA_UPDATES[next_version]))
                 self.set_schema_version(next_version)
             installed_version = self.installed_version
 
-    @classmethod
-    def set_schema_version(cls, version):
+    def set_schema_version(self, version):
         """Set the schema version (without running update scripts)."""
-        if version == cls.LATEST:
+        if version == self.LATEST:
             version = max(SCHEMA_UPDATES.keys())
-        with engine.begin() as connection:
+        with self.engine.begin() as connection:
             connection.execute(
                 sqlalchemy.text(
                     """

src/flickrhistory/database/models/__init__.py

@@ -13,19 +13,7 @@
 ]
 
 
-import sqlalchemy
-
-from ..engine import engine
-from .base import Base
-from ..databaseschemaupdater import DatabaseSchemaUpdater
 from .license import License
 from .photo import Photo
 from .tag import Tag
 from .user import User
-
-
-if sqlalchemy.inspect(engine).has_table(Photo.__table__.name):  # data exist
-    DatabaseSchemaUpdater().update_to_latest()
-else:
-    Base.metadata.create_all(engine)
-    DatabaseSchemaUpdater().set_schema_version(DatabaseSchemaUpdater.LATEST)

src/flickrhistory/database/photo_saver.py

@@ -8,7 +8,7 @@
 import datetime
 
 from .models import License, Photo, Tag
-from .engine import Session
+from .session import Session
 from .user_saver import UserSaver
 
 

src/flickrhistory/database/session.py

@@ -0,0 +1,57 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+
+"""An SQLAlchemy sessionmaker."""
+
+
+__all__ = ["Session"]
+
+
+import multiprocessing
+
+import sqlalchemy
+import sqlalchemy.orm
+
+from ..config import Config
+from .databaseschemaupdater import DatabaseSchemaUpdater
+from .models import Photo
+from .models.base import Base
+
+
+POOL_SIZE = multiprocessing.cpu_count() * 10
+
+
+class Session:
+    """An sqlachemy.Session."""
+
+    _sessionmaker = None
+
+    def __new__(cls, *args, **kwargs):
+        """Return an sqlachemy.Session."""
+        if cls._sessionmaker is None:
+            with Config() as config:
+                engine = sqlalchemy.create_engine(
+                    config["database_connection_string"],
+                    pool_size=POOL_SIZE,
+                    max_overflow=POOL_SIZE,
+                )
+
+            with engine.begin() as connection:
+                connection.execute(
+                    sqlalchemy.text(
+                        """
+                        CREATE EXTENSION IF NOT EXISTS
+                            postgis;
+                        """
+                    )
+                )
+
+            if sqlalchemy.inspect(engine).has_table(Photo.__table__.name):  # data exist
+                DatabaseSchemaUpdater().update_to_latest()
+            else:
+                Base.metadata.create_all(engine)
+                DatabaseSchemaUpdater().set_schema_version(DatabaseSchemaUpdater.LATEST)
+
+            cls._sessionmaker = sqlalchemy.orm.sessionmaker(engine, autoflush=False)
+        return cls._sessionmaker()

src/flickrhistory/database/user_saver.py

@@ -8,7 +8,7 @@
 import datetime
 
 from .models import User
-from .engine import Session
+from .session import Session
 
 
 __all__ = ["UserSaver"]