Hi,
well, I tested and it is as you assumed: QGIS deletes both datasets and
then issues an INSERT containing the new dataset. Therefore your foreign
key constraint throws the error. I see two workarounds:
1) as proposed before: change the foreign key behaviour. If that is not
possible
2) triggers might help you; possible outline:
a) preparation: add a field to operations and name it e.g. "was_parcel"
b) trigger 1, before delete:
update operations set was_parcel = parcel_id, set parcel_id = NULL
WHERE parcel_id = OLD.id (assuming parcel_id is the field with the
foreign key constraint)
c) trigger 2, after insert:
update operations set parcel_id = was_parcel, set parcel = NULL WHERE
parcel = NEW.id
Bernhard
Am 04.03.2015 10:36, schrieb Thibaut Gheysen:
Hi,
I do the merge interactively by selecting the 2 parcels and clicking on
the button "merge selected features" from the advanced digitizing
toolbar. On the "merge features attributes" window, I select the
attributes of the parcel A as attributes of the new/merged parcel. Like
that the new/merged parcel as the same primary key than the past parcel A.
Regarding the possibility to create triggers to clean the merge, I have
to think about it but seems a little bit complex given the number of
tables linked to parcel table (not only operation one) and also the fact
that during an editing session we can make multiple merge on the same time.
Regarding the type of foreign key, I have well "ON DELETE NO ACTION".
Defining the foreign key to "ON DELETE CASCADE" or "ON DELETE SET NULL"
is unfortunately not possible.
Best regards,
Thibaut.
2015-03-03 12:10 GMT+01:00 Bernhard Ströbl <[email protected]
<mailto:[email protected]>>:
Hi,
the question is how you define your foreign key [1], namely what you
put for "ON DELETE" (you have either NO ACTION or RESTRICT, which
throw the error you receive) If you set ON DELETE CASCADE the
operation would be deleted, too, probably not what you want. Maybe
you should set ON DELETE SET NULL (make sure that the field can be
NULL!). Afterwards you reconnect the operation and the new parcel.
Bernhard
[1]
http://www.postgresql.org/__docs/current/static/ddl-__constraints.html#DDL-__CONSTRAINTS-FK
<http://www.postgresql.org/docs/current/static/ddl-constraints.html#DDL-CONSTRAINTS-FK>
Am 03.03.2015 11:14, schrieb Thibaut Gheysen:
Hi,
I would like to have your opinion in order to simplify as much as
possible our current workflow.
We have a table parcel and a table operation. The table operation
include a foreign key to the table parcel. We have 2 parcels (A
and B)
but only parcel A has operations link on it. I would like to
merge the 2
parcels by keeping the attributes of the parcel A. The merge is
doing
properly but impossible to save the edit (Provider errors:
PostGIS error
while deleting feature: ERROR: update or delete table "parcel"
violates
foreign key constraint"fk_parcel" on table "operation"). I guess
this is
due to the fact the Qgis first delete the 2 parcels (A and B) before
creating a new one (merged one).
This behaviour oblige us to export the table parcel into a
shapefile and
make the modifications on it. Once done, we import the shapefile
into
PostGIS and update the parcel geometry base on it.
Is there any chance to find an easier workflow, without developing a
plug-in ?
Thank for your help.
Best regards,
Thibaut.
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