What I'm doing, and sorry for not explaining further, is making a CSV
file of data. Each row is a row in my results, or would be if I were
just selecting from products. Having to select from attributes as well
is where I'm having problems. Each product can have multiple
attributes, and each attribute value can be assigned to multiple
products. Joining everything (by using filter()) is giving me way too
many results to deal with effectively.
Say we had a product with an ID of 001, a name of "widget", and an
image of "images/001.jpg". This product has a weight and a color, but
those attributes are in the attributevalues table.
Attributes work something like this: attributeassignments has a
product ID and an attribute ID. Attributes has an attribute ID and an
attribute name ("color", "size", and so on). AttributeValues has an
attribute ID and a value ("blue", "55", etc).
For our widget, attributes might have 001, 001, "size"; 001, 002,
"color"; 001, 003, "weight". 001 is the product ID of the widget.
AttributeAssignment might have 001, 001; 001, 002; 001, 003. 001 is
the widget, and the second numbers are the IDs of the different
attributes.
AttributeValues might have 001, "1x2x3"; 002, "blue"; 003, "55".
In the CSV file, I want to put each of those three attributes under a column:
001, Widget, images/001.jpg, blue, 55, 1x2x3
Currently, I'm iterating over the results. The first line inside the
loop, I check the current result's ID and compare it to the previous
one. If they match, I assume I'm on the same result, so I get the
values of the attributes in the row. If the two IDs differ, I assume
I'm done. I write out the values for the last result, clear out the
array I use to store all the values, and grab the new values that
aren't attributes.
My current query does so much joining that my results are too large to
manage, though. The very first iteration works perfectly, but then I
get stuck with the same product ID number. Even when I raise the query
limit to 100,000, I never see any other product ID than that first
one. It feels like an infinite loop, but my loop is simply,
items = <my query>
for result in items:
...
I hope this makes more sense. I've re-read the ORM tutorial as
Jonathan suggested, too. The last bit, about many-to-many
relationships, seems like it might be useful. I don't quite follow it
all, but hopefully some of it will make more sense the more I re-read
it.
On 3/10/16, Jonathan Vanasco <jonat...@findmeon.com> wrote:
> 2 comments:
>
> 1. Go through the SqlAlchemy ORM tutorial. What you're describing right
> now is dancing around some very basic relationship definition and
> loading/query techniques.
>
> 2. You haven't described what you actually want to accomplish, only some
> general ideas of how you think you could interact with data. If you want
> to grab a matrix that has every product, there will be one set of ways to
> approach the problem. If you want to return an iterable list of all
> variations of a certain product, there will be another set of ways. If you
>
> want to search by specific criteria, there will be yet another set of ways.
>
> depending on what you do with the data, the query will be different.
>
>
>
>
>
> --
> 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.
> To post to this group, send email to sqlalchemy@googlegroups.com.
> Visit this group at https://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.
To post to this group, send email to sqlalchemy@googlegroups.com.
Visit this group at https://groups.google.com/group/sqlalchemy.
For more options, visit https://groups.google.com/d/optout.
