hi
in a class hierarcy A,B,C,...
in order to get "all things that are instances of a subclass of A but
not A itself", i used somequery().from-statement( subfilter).
then i found select_from() which allows to do further joins/filter etc
and now use that.
but it won't work for polymorphic queries with unions, e.g. concrete
inheritance (pseudocode):
m = mapper(A, with_polymorphic = ('*',
polymunion( A:..., B:..., C:..., ... ), alias=pu_a)
)
allsubs = ses.query(A).select_from(
polymunion( B:.., C:.. ), alias=psub_a) #same as above less A
)
this seems to do a vector product:
SELECT psub_a.*
FROM (SELECT "B".db_id AS db_id, "B".name AS name, "B"."dataB"
AS "dataB", 'B' AS atype FROM "B") AS psub_a,
(SELECT "A".db_id AS db_id, "A".name AS name, CAST(NULL AS
VARCHAR(200)) AS "dataB", 'A' AS atype
FROM "A" UNION ALL SELECT "B".db_id AS db_id, "B".name AS
name, "B"."dataB" AS "dataB", 'B' AS atype
FROM "B") AS pu_a
...
is this bug or?
and, is this the correct way to do this stuff?
the other way i can imagine is
ses.query(A).filter( A.type != 'Aidentity') - but isn't this more
expensive?
svil
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