I want to maintain some groups that change over time. Specifically, I have a group table with group names and other attributes. Every time an item enters a group, a record is created in an item table with an entry timestamp (and some other attributes). Whenever an item leaves a group, its item table record is updated with an exit timestamp. I need to access the group as it was at any specific time. I cannot find a nice way with SQLAlchemy ORM to maintain such a Group object with its Item collection.
The problem seems to be controlling the contents of a collection in an ORM object. Using joins I can limit the returned objects to ones that have certain traits in the associated collection but the collection itself always has all the collectable objects. In the orm tutorial, the section "Selecting Entities from Subqueries" comes close. That query returns the user (with all its associated addresses) and a list of the desired addresses. Is there any way to get the User object "jack" with only the filtered addresses it the "addresses" collection of the object? One way to do this is to set up the relation to filter the objects (addresses) that appear in the collection (user.addresses). I do not want to do this because I want build the query after the mapping is done (e.g. give me all users that use gmail or something else for email). Is this the same question as asked in "filter relation based on column values" where the recommnendation was to subclass Query? Similar threads are "Extended Query subclass with add_named_column method" and "Optimizing joined entity loads". Dynamic Relation Loaders in the SQLAlchemy documentation has an approach where the collection is returned as a Query object which can be filtered. It seems that one can initialize, append to, and remove from the collection (query) but the interface requires the filter to be specified and SQL is generated whenever the collection is accessed. What is the best way to solve this problem? --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
