Michael, thank you for you reply, I expected you to mention from_self :) I
know about it, it is a handy trick indeed
But I deliberately don't use it, because this way I don't know how to
mention a column which I want to filter on
This is due to the fact, that it is calculated i.e. there is no table to
refer to! I might resert to using literals("filter('avg_1>10')"), but 'd
prefer to stay in the more ORM-style
суббота, 25 апреля 2015 г., 2:37:11 UTC+5 пользователь Michael Bayer
написал:
>
>
>
> On 4/24/15 5:25 PM, Пайков Юрий wrote:
>
>
> q = session.query(Recipe, func.avg(Recipe.field1).over(...)).join(...)
>
> I have a query which selects some mapped entity as well as other columns.
>
> I then refer to the name of that entity when working with the result of
> the query:
> for entry in q.all():
> recipe=entry.Recipe
> ....
>
> Now, I want to add filtering by some calculated criteria to my query, and
> so I wrap it in an additional query:
> q = q.subquery();
> q = session.query(q).filter(q.c.avg_1 > 10 )
>
> However, this way I can no longer access entry.Recipe! Is there a way to
> make sqlalchemy adapt names? I tried aliased and select_entity_from, but no
> luck :(
>
>
> this is getting into less reliable stuff, but instead of subquery() ->
> session.query(q), use the from_self() method. It's designed to work this
> way, and your Recipe entity will be adapted into the subquery.
>
> I've observed that the vast majority of my users don't seem to get into
> queries like these, so from_self() is not as popular (or widely tested) as
> it should be, but it is at the base of a lot of widely used functions like
> count() and subquery eager loading, so give it a try:
>
>
> http://docs.sqlalchemy.org/en/rel_1_0/orm/query.html?highlight=from_self#sqlalchemy.orm.query.Query.from_self
>
> apparently it needs some documentation too :)
>
>
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