On Oct 20, 2011, at 3:54 PM, Jeremy Jones wrote:
> We are moving from mysql to postgres and would like to have the same
> sort behavior in postgres that mysql provides. Unfortunately as the
> code was written for our application, it didn't always get an explicit
> "order by" because the behavior that was in mysql worked how it was
> "supposed to." Is there any way that we can get sqlalchemy to enforce
> for postgres the "order by {{ primary key field }} nulls last" that we
> saw in mysql? To add a wrinkle, we are using Elixir and not straight
> SQLAlchemy, but I suspect that we are going to have to address this at
> the SA level rather than the Elixir level.
mapper() accepts an "order_by" parameter that would provide, in simple cases, a
default "order by" for a query() that doesn't otherwise specify "order_by".
Similarly, relationship() also has an "order_by" parameter that provides for
the ORDER BY to be used whenever a related collection is loaded.
Elixir should provide some mechanism to pass these configuration options down
to the underlying mapper() and relationship() functions.
http://www.sqlalchemy.org/docs/orm/mapper_config.html#class-mapping-api
http://www.sqlalchemy.org/docs/orm/relationships.html#relationships-api
Generally any relationship() that's against a list-based collection should
probably have the order_by parameter since Python lists themselves have a
deterministic ordering.
the "nulls last" part, while available as an option, isn't needed here since a
primary key value cannot be NULL.
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