thanks Mike!when i stated about the limit, it was because it must not be taken as a parameter for any query, which "select * from blah" and "select * from bla limit N" should be return the same exactly number of rows, including where filters and so on. it is something like a "physical" rule, where my parent is (really) a box and the children its items (so, i cannot put more items then the box's limit).
either way, creating a relationship with limit *can* provide me that sort of behaviour?
i mean, i'm just asking this because it may be already done by someone. if not, that's not a problem -- i'll have to managed something by myself :)
ps: sorry for my bad english, sometimes i can't make understandable questions :)
best regards, richard. On 05/19/2015 11:16 AM, Mike Bayer wrote:
On 5/19/15 8:57 AM, Richard Gerd Kuesters wrote:hi!this may be a weird question, but is there a way i can restrict the number of children in a relationship? not by limit ...how is that different? Anytime in SQL you want to get only the first N of M, LIMIT or its equivalents must be involved.two options are:1. write the exact SQL for the primary + relationship you want, then use contains_eager() to specify it as a collection load. the SQL has to be along the lines of "SELECT * FROM primary LEFT OUTER JOIN secondary WHERE secondary.id IS NULL or secondary.id IN (select id FROM secondary AS sec_2 LIMIT N WHERE sec_2.primary_id=secondary.primary_id)2. load the collections individually: from sqlalchemy.orm.attributes import set_committed_value for item in things: child_items = sess.query(Child).with_parent(item).limit(N).all() set_committed_value(item, "child_items", child_items)scenario: i have a one to many rel, where the parent have 3 values (row, column, depth) that creates a max child count of row * column * depth (yes, like the 3d stuff) ... so, count(child) >= max_child, this sort of stuff.if i could pull of postgres specific constraint for this, even better ... best regards, richard. --You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com <mailto:sqlalchemy+unsubscr...@googlegroups.com>. To post to this group, send email to sqlalchemy@googlegroups.com <mailto:sqlalchemy@googlegroups.com>.Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.--You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com <mailto:sqlalchemy+unsubscr...@googlegroups.com>. To post to this group, send email to sqlalchemy@googlegroups.com <mailto:sqlalchemy@googlegroups.com>.Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
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