On Wed, Mar 11, 2009 at 10:31 AM, Madhusudan C.S <[email protected]>wrote:
> Hi all,
> I wanted to fix this bug. I just went through the code to see what was
> happening. For the same sample code given in the ticket, these were my
> findings:
>
> The schema generated looks like this and there is no issue with it:
> CREATE TABLE "testapp_childmodel" (
> "parentmodel_ptr_id" integer NOT NULL PRIMARY KEY REFERENCES
> "testapp_parentmodel" ("id"),
> "text" text NOT NULL
> );
> CREATE TABLE "testapp_parentmodel" (
> "id" integer NOT NULL PRIMARY KEY,
> "slug" varchar(50) NOT NULL
> );
> CREATE TABLE "testapp_parentmodel_links" (
> "id" integer NOT NULL PRIMARY KEY,
> "from_parentmodel_id" integer NOT NULL REFERENCES "testapp_parentmodel"
> ("id"),
> "to_parentmodel_id" integer NOT NULL REFERENCES "testapp_parentmodel"
> ("id"),
> UNIQUE ("from_parentmodel_id", "to_parentmodel_id")
> );
>
> CREATE INDEX "testapp_parentmodel_slug" ON "testapp_parentmodel" ("slug");
>
> I inserted test1, test2 and test3(all names being values of slug field) to
> ParentModel and linked test1 and test3 to test2 through links field. There
> seems to be no issues. Then I inserted testc1, testc2 and testc3 to
> ChildModel and linked testc2 and testc3 to testc1 through inherited links
> field. Now I can see only to links, i.e
> I get these results in the interactive interpreter:
>
> >>> from dummy.testapp.models import ParentModel, ChildModel
> >>> c1 = ChildModel.objects.get(slug='testc1')
> >>> c2 = ChildModel.objects.get(slug='testc2')
> >>> c3 = ChildModel.objects.get(slug='testc3')
> >>> c1.links.all()
> []
> >>> c2.links.all()
> [<ParentModel: testc1>]
> >>> c3.links.all()
> [<ParentModel: testc1>]
>
> This means only to links are being queried and not from links for the
> inherited model. I just saw how the queries are working and these are the
> queries constructed for c1, c2 and c3 respectively.
>
> SELECT "testapp_parentmodel"."id", "testapp_parentmodel"."slug" FROM
> "testapp_parentmodel" INNER JOIN "testapp_parentmodel_links" ON
> ("testapp_parentmodel"."id" =
> "testapp_parentmodel_links"."to_parentmodel_id") WHERE
> "testapp_parentmodel_links"."from_parentmodel_id" = 4 LIMIT 21
>
> SELECT "testapp_parentmodel"."id", "testapp_parentmodel"."slug" FROM
> "testapp_parentmodel" INNER JOIN "testapp_parentmodel_links" ON
> ("testapp_parentmodel"."id" =
> "testapp_parentmodel_links"."to_parentmodel_id") WHERE
> "testapp_parentmodel_links"."from_parentmodel_id" = 5 LIMIT 21
>
> SELECT "testapp_parentmodel"."id", "testapp_parentmodel"."slug" FROM
> "testapp_parentmodel" INNER JOIN "testapp_parentmodel_links" ON
> ("testapp_parentmodel"."id" =
> "testapp_parentmodel_links"."to_parentmodel_id") WHERE
> "testapp_parentmodel_links"."from_parentmodel_id" = 6 LIMIT 21
>
> From what I see the queries must be actually UNION of two queries which
> fetch data both from, "from" and "to" fields in the
> "testapp_parentmodel_links" table.It should look some thing like this, from
> what I have understood:
>
> SELECT "testapp_parentmodel"."id", "testapp_parentmodel"."slug" FROM
> "testapp_parentmodel" INNER JOIN "testapp_parentmodel_links" ON
> ("testapp_parentmodel"."id" =
> "testapp_parentmodel_links"."to_parentmodel_id") WHERE
> "testapp_parentmodel_links"."from_parentmodel_id" = 4 LIMIT 21
> UNION
> SELECT "testapp_parentmodel"."id", "testapp_parentmodel"."slug" FROM
> "testapp_parentmodel" INNER JOIN "testapp_parentmodel_links" ON
> ("testapp_parentmodel"."id" =
> "testapp_parentmodel_links"."from_parentmodel_id") WHERE
> "testapp_parentmodel_links"."to_parentmodel_id" = 4 LIMIT 21
>
> Is this an elegant approach? If so can some one help me implement this? I
> went through the code of QuerySet, Manager classes and other parts of
> django.db.models. How to go about from here? I am very keen on fixing this
> issue. Kindly help me.
>
> --
> Thanks and regards,
> Madhusudan.C.S
>
> Blogs at: www.madhusudancs.info
> Official Email ID: [email protected]
>
> P.S: I am really sorry if the text is not wrapped. I am still not
> understanding how wrapping works here. Will correct it from next mail. Hope
> Auto text wrapping works.
>
> >
>
This looks like it may just be a symptom of
http://code.djangoproject.com/ticket/10237 if I'm reading htis correctly.
Alex
--
"I disapprove of what you say, but I will defend to the death your right to
say it." --Voltaire
"The people's good is the highest law."--Cicero
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