[sqlalchemy] Best practice for binding the engine
From reading the documentation I learned that you can either bind an engine
to a session:
engine = create_engine('sqlite:///{}'.format(dbPath), echo=False)
Session = sessionmaker(bind=engine)
or to a declarative_base:
engine = create_engine('sqlite:///{}'.format(dbPath), echo=False)
Sqlalchemy_base = declarative_base(engine)
Is there a best practice like always binding to a session?
I currently bind the engine to both:
engine = create_engine('sqlite:///{}'.format(dbPath), echo=False)
Session = sessionmaker(bind=engine)
Sqlalchemy_base = declarative_base(engine)
From running my codes I didn't encounter any problem. But I wonder how
SqlAlchemy resolves the conflict internally if there are two bindings? Is
there some potential problems down the road if I kept using this manner?
Thanks.
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[sqlalchemy] databases and asynchronous programming
Hi All, So, one of the projects I'm playing with at the moment is a big ball of asynchronous networking (tonnes of protocols, some tcp, some multicast) which I want to stick a webapi onto (normal requests + websocket) and probably do some database interaction with. So, aside from figuring out which async path to go (twisted, tornado, tulip or good old fashioned asyncore), I have some concerns about database interaction. First question: I'm guessing I should do all database access in a spawned off thread, lest it blocks? Second question: if I end up using the ORM, I guess a safe approach would be to expunge the objects from the session before I return them from the thread that does the db interaction? Any other advice people have in this area? cheers, Chris -- Simplistix - Content Management, Batch Processing Python Consulting - http://www.simplistix.co.uk -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
[sqlalchemy] Cascade Delete, session confusion
Hi all,
I just started using SQLA, and I am confused by some cascade delete
behaviour I am seeing. Please see the code and tests below which show that
the session is seeing table rows in one area and not in the other:
CODE:
print Product1Mod3
__tablename__ = 'products'
id = Column(Integer, primary_key=True)
product_name = Column(String(250), unique=True)
vendor_id = Column(Integer, ForeignKey('vendors.id'), nullable=False)
vendor = relationship('Vendor', backref = backref('products',
order_by=id, cascade=all, delete-orphan))
def __init__(self, product_name, vendor_id):
self.product_name = product_name
self.vendor_id = vendor_id
def __repr__(self):
return 'Product: %r Product ID: %r Vendor ID: %r' %
(self.product_name, self.id, self.vendor_id)
class Module(Base):
__tablename__ = 'modules'
id = Column(Integer, primary_key=True)
module_name = Column(String(250), unique=True)
product_id = Column(Integer, ForeignKey('products.id'), nullable=False)
product = relationship('Product', backref = backref('modules',
order_by=id, cascade=all, delete-orphan))
def __init__(self, module_name, product_id):
self.module_name = module_name
self.product_id = product_id
def __repr__(self):
return 'Module: %r Module ID: %r Product ID: %r' %
(self.module_name, self.id ,self.product_id)
TESTING:
msg('Module Tests')
Product2Mod1 = Module('Product2Mod1',1)
Product2Mod2 = Module('Product2Mod2',1)
Product1Mod1 = Module('Product1Mod1',2)
Product1Mod2 = Module('Product1Mod2',2)
Product1Mod3 = Module('Product1Mod3',2)
db_session.add(Product2Mod1)
db_session.add(Product2Mod2)
db_session.add(Product1Mod1)
db_session.add(Product1Mod2)
db_session.add(Product1Mod3)
db_session.commit()
msg(Product2Mod1 Product:)
print Product2Mod1.product
msg('delete tests')
print Query to show all products: \n
print Product.query.all()
print \nQuery to show all modules: \n
print Module.query.all()
print \ndeleting product 1: db_session.delete(Product1) --
db_session.commit()
db_session.delete(Product1)
db_session.commit()
print \nQuery to check for changes with products and modules, shows that
the modules and product are gone:\n
print Product.query.all()
print Module.query.all()
print \nThe modules below belong to the deleted product, they should have
disappeared, but do not: -- NOT SURE WHY THIS IS HAPPENING
print Product1Mod1
print Product1Mod2
print Product1Mod3
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[sqlalchemy] Re: Cascade Delete, session confusion
I also looked at this through SQLite database browser, and the database is correct, so is this a Python side error? -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
[sqlalchemy] Re: databases and asynchronous programming
I'm using twisted and looking to move raw SQL ( via twisted's `runInteraction` ) into my SqlAlchemy model. I've only played with it a bit. A few notes: Under Twisted you can't have threads spawned threads. Your computer will want to die. I did and crashed the server several times, daily. My app originally had some work done in deferToThread(), which then spawned off some DB specific stuff in the `runInteraction`. Every 3-6hours the app would crash and restart. The fix I chose was to do everything in the runInteraction (I lost the deferToThread layer). Conceivably, one could use deferToThread instead of runInteraction, and then run SqlAlchemy in there directly. Someone posted a few weeks ago about using one of the extra arguments to ScopedSession to get it running with Twisted. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
Re: [sqlalchemy] Cascade Delete, session confusion
On Mar 9, 2014, at 3:18 PM, Dmitry Berman dmikha...@gmail.com wrote: print \nQuery to check for changes with products and modules, shows that the modules and product are gone:\n print Product.query.all() print Module.query.all() print \nThe modules below belong to the deleted product, they should have disappeared, but do not: -- NOT SURE WHY THIS IS HAPPENING print Product1Mod1 print Product1Mod2 print Product1Mod3 not sure what you're expecting there, are you expecting that the Product1Mod1 symbol would be modified within your interpreter to be None? Python can't do that under normal circumstances. A variable always points to the thing that it was assigned to, there's no (normal, non-hacky) mechanism by which variables change into None without explicitly being reassigned. Those product objects represent what used to be in those rows. They have a deleted flag you can see: from sqlalchemy import inspect inspect(deleted_product).deleted True -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
[sqlalchemy] tracking history across a 'flush()'
I have some lightweight revision tracking on some models. I generate a diff based on the history of the object (via inspector). a limitation I just realized, is that this history only dates back to the most recent flush() -- it doesn't date back to the initial load. are there any existing facilities that would let me access the originally loaded attributes -- prior to any flushes ? thankfully i don't need this functionality, my code works fine as-is. i'd just like to be safe and use anything better if available. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
Re: [sqlalchemy] Cascade Delete, session confusion
This makes a lot of sense, I just didn't realize how it worked... *When I did the following:* print inspect(Product1Mod1).deleted print inspect(Product1Mod2).deleted print inspect(Product1Mod3).deleted *Instead of just:* print Product1Mod1 print Product1Mod2 print Product1Mod3 This returned: True True True And this makes total sense now. Thanks. On Sunday, March 9, 2014 7:22:49 PM UTC-4, Michael Bayer wrote: On Mar 9, 2014, at 3:18 PM, Dmitry Berman dmik...@gmail.com javascript: wrote: print \nQuery to check for changes with products and modules, shows that the modules and product are gone:\n print Product.query.all() print Module.query.all() print \nThe modules below belong to the deleted product, they should have disappeared, but do not: -- NOT SURE WHY THIS IS HAPPENING print Product1Mod1 print Product1Mod2 print Product1Mod3 not sure what you’re expecting there, are you expecting that the “Product1Mod1” symbol would be modified within your interpreter to be None? Python can’t do that under print inspect(Product1Mod1).deleted print inspect(Product1Mod2).deleted print inspect(Product1Mod3).deletednormal circumstances. A variable always points to the thing that it was assigned to, there’s no (normal, non-hacky) mechanism by which variables change into “None” without explicitly being reassigned. Those product objects represent what used to be in those rows. They have a “deleted” flag you can see: from sqlalchemy import inspect inspect(deleted_product).deleted True -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
[sqlalchemy] [ANN] SQLTap - SQL profiling and introspection for SQLAlchemy applications
A few years ago, I built SQLTap, a simple library to hook into SQLAlchemy and pull out statistics and information on the queries you ran. This last couple days I've overhauled it an updated it to make it more useful! You basically just start the profiler and then it can dump out nice browsable HTML reports like this: http://sqltap.inconshreveable.com/_images/sqltap-report-example.png SQLTap helps you answer questions like: What queries is my application running? How long do they take on average? At maximum? At minimum? At median? What sequences of function calls lead to each invocation of a query? Where in my source code is the query executed? The latest updates and improvements make up sqltap version 0.3 and include: - The report now has a sexy new HTML UI based on bootstrap3. - You can add sqltap to any WSGI application and get a live, updating dashboard of all the queries going through an application. - The WSGI integration has controls to enable/disable the profiling at any time so you can even include it in production applications for selective profiling. - The library's API is now greatly improved, allowing you to do your own real-time collection of statistics as well as allowing you to create individual profilers for different engines instead of forcing a global profiler. - Updated/improved documentation Install with: pip install sqltap And in your code: import sqltap profiler = sqltap.start() # sometime later after queries have been run sqltap.report(profiler.collect(), report.html) Links for reference: Code and some documentation (star it!): https://github.com/inconshreveable/sqltap Documentation: http://sqltap.inconshreveable.com/ On PyPI: https://pypi.python.org/pypi/sqltap Enjoy! - alan -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
Re: [sqlalchemy] tracking history across a 'flush()'
On Mar 9, 2014, at 8:25 PM, Jonathan Vanasco jonat...@findmeon.com wrote: I have some lightweight revision tracking on some models. I generate a diff based on the history of the object (via inspector). a limitation I just realized, is that this history only dates back to the most recent flush() -- it doesn't date back to the initial load. are there any existing facilities that would let me access the originally loaded attributes -- prior to any flushes ? thankfully i don't need this functionality, my code works fine as-is. i'd just like to be safe and use anything better if available. pretty much just rollback() is what we have there :). a long time ago I looked into seeing if the attributes could actually store multiple savepoints and have rollback built in and all that, and determined it would be enormously complicated and have a lot of nasty edge cases too. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
Re: [sqlalchemy] [ANN] SQLTap - SQL profiling and introspection for SQLAlchemy applications
hey that looks pretty nice, ill give it a shoutout. On Mar 9, 2014, at 9:21 PM, Alan Shreve a...@inconshreveable.com wrote: A few years ago, I built SQLTap, a simple library to hook into SQLAlchemy and pull out statistics and information on the queries you ran. This last couple days I've overhauled it an updated it to make it more useful! You basically just start the profiler and then it can dump out nice browsable HTML reports like this: http://sqltap.inconshreveable.com/_images/sqltap-report-example.png SQLTap helps you answer questions like: What queries is my application running? How long do they take on average? At maximum? At minimum? At median? What sequences of function calls lead to each invocation of a query? Where in my source code is the query executed? The latest updates and improvements make up sqltap version 0.3 and include: - The report now has a sexy new HTML UI based on bootstrap3. - You can add sqltap to any WSGI application and get a live, updating dashboard of all the queries going through an application. - The WSGI integration has controls to enable/disable the profiling at any time so you can even include it in production applications for selective profiling. - The library's API is now greatly improved, allowing you to do your own real-time collection of statistics as well as allowing you to create individual profilers for different engines instead of forcing a global profiler. - Updated/improved documentation Install with: pip install sqltap And in your code: import sqltap profiler = sqltap.start() # sometime later after queries have been run sqltap.report(profiler.collect(), report.html) Links for reference: Code and some documentation (star it!): https://github.com/inconshreveable/sqltap Documentation: http://sqltap.inconshreveable.com/ On PyPI: https://pypi.python.org/pypi/sqltap Enjoy! - alan -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
