[sqlalchemy] Re: SA ORM Tutorial: Query
On Feb 26, 2009, at 12:40 AM, a.fowler wrote: Hello, A couple of questions on the tutorial: 1) Why .all() in 3rd (and some others) query code box, but not others? .all() is essentially equivalent to list(query). Some of the examples already iterate the query, such as for x in query: print x, others don't - but the tutorial wants you to see the results. Ideally none of the examples would use all() since you generally iterate to get results. 2) Filter clause: Why '==' vs. '=' used in .filter() vs. .filter_by () the argument signature of filter() is: filter(argument) whereas that of filter_by() is: filter_by(**kwargs) the argument is a clause expression. SQLAlchemy generates clause expressions when you call overridden Python operators like == (__eq__()) and similar. The SQL expression tutorial spends a little more time on this concept. 3) Common Filter Operators: Why or_(), and_(), in_(), but like(). (instead of like_() ) or/and/in are Python reserved words, it's convention per pep8 to rename functions/variables with a trailing underscore if they conflict. 4) Common Filter Operators: Is '!= None' the correct way to get a NOT NULL? (Not mentioned in tutorial) that will work yes 5) Common Filter Operators: Using User.name.match raised an (OperationalError) unable to use function MATCH in the requested context... why? (using sqlite:memory is per tutorial) MATCH is not supported by every database, SQLite is apparently one of them. I'm a little surprised that operator found its way into the tutorial since I've never used it --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
[sqlalchemy] Re: SA ORM Tutorial: Query
A couple of questions on the tutorial: 1) Why .all() in 3rd (and some others) query code box, but not others? .all() is essentially equivalent to list(query). Some of the examples already iterate the query, such as for x in query: print x, others don't - but the tutorial wants you to see the results. Ideally none of the examples would use all() since you generally iterate to get results. Ah OK. Why or_(), and_(), in_(), but like(). (instead of like_() ) or/and/in are Python reserved words, it's convention per pep8 to rename functions/variables with a trailing underscore if they conflict. I see. 4) Common Filter Operators: Is '!= None' the correct way to get a NOT NULL? (Not mentioned in tutorial) that will work yes 5) Common Filter Operators: Using User.name.match raised an (OperationalError) unable to use function MATCH in the requested context... why? (using sqlite:memory is per tutorial) MATCH is not supported by every database, SQLite is apparently one of them. I'm a little surprised that operator found its way into the tutorial since I've never used it Thank you. A very clear explanation. :) I don't know if the docs team reads this, but here are a couple of comments: 1) Perhaps re-emphasize, in a few more places, SA's overloading of the logical operators. I had forgotten that by the time I got to the query filter section. 2) Since there are two alternative paths to take take in the class / table building part (mapper / declarative), it not clear what the prerequisites are for the 2nd path. To fix this, please show resetting the python interpreter after the mapper example, and re-importing all that is actually needed for the declarative version. 3) Mention the right way to filter by NOT NULL. 4) Mention the reservedword_() naming convention in passing. It should be known to Python programmers, but since this is a tutorial, it could be there are new Python users here as well. 5) Since the tutorial actually shows using SQLite, mention that the .match() directive is not supported by SQLite. I hope to finish the tutorial over the next few days, and may have more comments then. --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
[sqlalchemy] Re: SA ORM Tutorial: Query
On Feb 26, 2009, at 11:49 AM, a.fowler wrote: I don't know if the docs team reads this, but here are a couple of comments: I'm pretty much the documentation team :).but my time is very short these days, would you be interested in submitting a patch against the documentation source file ? It's written in ReST format and can be found in the distribution/current trunk in doc/build/ ormtutorial.rst . I can quickly review your patches and integrate them with the current documentation. the docs can also be built if you type make html in that directory. --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
