Re: [sqlalchemy] Re: all
On Jul 11, 2012, at 8:27 PM, Gunnlaugur Briem wrote: Hi burgiduroy, On Wednesday, 11 July 2012 15:24:59 UTC, burgiduroy wrote: Are there any performance difference between the two? for row in query_object.all(): do_something() AND for row in query_object: do_something() The first fetches and processes all rows in one go before executing the loop body. The second streams them in. How much that really matters depends on the DBAPI (it may fetch all rows in one go anyway), and maybe on how heavy the object mapping is ... and on whether you end up exiting your loop early (and so avoid processing the rest unnecessarily). Well, assuming this is an ORM Query, the Query object internally processes all the rows before yielding them regardless, unless you used the yield_per() method to configure that it should process them in batches. Unfortunately the Query can't unconditionally yield rows at a time due to the fact that the same mapped object can be present multiple times across many rows, as a result of explicit joins as well as loads of related collections, and mapped objects are mutable. So normally there's no real difference in memory usage between iter(query) and query.all(), and none for performance except for the small overhead of the extra list(self) that query.all() uses. -- 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.
Re: [sqlalchemy] Re: all
So which is the best practice? for row in query or for row in query.all() On Thu, Jul 12, 2012 at 8:54 PM, Michael Bayer mike...@zzzcomputing.comwrote: On Jul 11, 2012, at 8:27 PM, Gunnlaugur Briem wrote: Hi burgiduroy, On Wednesday, 11 July 2012 15:24:59 UTC, burgiduroy wrote: Are there any performance difference between the two? for row in query_object.all(): do_something() AND for row in query_object: do_something() The first fetches and processes all rows in one go before executing the loop body. The second streams them in. How much that really matters depends on the DBAPI (it may fetch all rows in one go anyway), and maybe on how heavy the object mapping is ... and on whether you end up exiting your loop early (and so avoid processing the rest unnecessarily). Well, assuming this is an ORM Query, the Query object internally processes all the rows before yielding them regardless, unless you used the yield_per() method to configure that it should process them in batches. Unfortunately the Query can't unconditionally yield rows at a time due to the fact that the same mapped object can be present multiple times across many rows, as a result of explicit joins as well as loads of related collections, and mapped objects are mutable. So normally there's no real difference in memory usage between iter(query) and query.all(), and none for performance except for the small overhead of the extra list(self) that query.all() uses. -- 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. -- 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: all
Hi burgiduroy, On Wednesday, 11 July 2012 15:24:59 UTC, burgiduroy wrote: Are there any performance difference between the two? for row in query_object.all(): do_something() AND for row in query_object: do_something() The first fetches and processes all rows in one go before executing the loop body. The second streams them in. How much that really matters depends on the DBAPI (it may fetch all rows in one go anyway), and maybe on how heavy the object mapping is ... and on whether you end up exiting your loop early (and so avoid processing the rest unnecessarily). Regards, Gulli -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To view this discussion on the web visit https://groups.google.com/d/msg/sqlalchemy/-/rtdpsUfOa1QJ. 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: *all* *new* *tutorials* !!!!
This *IS* some piece of work ! Mike, you are the One ! :) Regards, -- Alexandre CONRAD --~--~-~--~~~---~--~~ 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 [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
[sqlalchemy] Re: *all* *new* *tutorials* !!!!
Cool. thx Michael! On 8/7/07, Michael Bayer [EMAIL PROTECTED] wrote: Hi gang - The documentation for 0.4 is undergoing tremendous changes, and is now released, in its almost-there format, at http://www.sqlalchemy.org/docs/04/ . The goal with these docs is not just to update to new 0.4 paradigms, but to also raise the bar for accuracy and clarity. Of major note is that the datamapping and sql construction sections, as well as the old tutorial, have been entirely replaced by two new and very comprehensive tutorials, one targeted at ORM and the other at SQL Expression Language. Both have no prerequisites to start, they each can be the first thing you ever read about SQLAlchemy. Both are also fully executable doctest format, so they are guaranteed not to have my usual array of mistakes. Also here is a rewritten mapper configuration document to replace advanced datamapping. It includes clearer, up-to-date, and more correct examples of virtually every major mapper pattern we have, including all the new stuff like dynamic relations. With recently updated engine and metadata sections, the only major section left is sessions, which already includes information about the new autoflush and transactional sessions, as well as two-phase and SAVEPOINT recipes...I hope to simplify some of the older content here as well as standardize on the new sessionmaker function and its cousin, scoped_session, which replaces SessionContext as well as assignmapper (both are deprecated in 0.4). I hope everyone can check out the docs, come back with feedback/ corrections/questions, and start getting ready for 0.4 ! - mike -- Cheers, - A --~--~-~--~~~---~--~~ 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 [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
[sqlalchemy] Re: all() or list() ?
On 8/1/07, Gaetan de Menten [EMAIL PROTECTED] wrote: On 8/1/07, Alexandre CONRAD [EMAIL PROTECTED] wrote: I'm realizing that I've been using .list() to query objects. But all the examples in the docs talk about .all(). What's the difference ? Should I switch to .all() rather than .list() ? Will list be deprecated in 0.4 ? Exactly. list() is the old way, all() is the 0.4 way. .list() is the old new way, or short-lived new way. .all() is the real new way. -- Mike Orr [EMAIL PROTECTED] --~--~-~--~~~---~--~~ 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 [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
[sqlalchemy] Re: all() or list() ?
On 8/1/07, Alexandre CONRAD [EMAIL PROTECTED] wrote: I'm realizing that I've been using .list() to query objects. But all the examples in the docs talk about .all(). What's the difference ? Should I switch to .all() rather than .list() ? Will list be deprecated in 0.4 ? Exactly. list() is the old way, all() is the 0.4 way. -- Gaëtan de Menten http://openhex.org --~--~-~--~~~---~--~~ 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 [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
[sqlalchemy] Re: all() or list() ?
Gaetan de Menten wrote: What's the difference ? Should I switch to .all() rather than .list() ? Will list be deprecated in 0.4 ? Exactly. list() is the old way, all() is the 0.4 way. Thanks Gaetan, I'll clean up my code to be compliant with 0.4. Regards, -- Alexandre CONRAD --~--~-~--~~~---~--~~ 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 [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
