On Tuesday, February 23, 2016 at 5:44:45 PM UTC+1, Mike Bayer wrote:
Mike, thank you for your reply and help.
well the first thing is you definitely don't need
> UniqueConstraint('lang_id', 'text_id') because these columns are already
> in the primary key.
>
Noted.
> the next issue in this test at least is that you're referring to the
> primary key of a row in Lang but there is no Lang row being created
> here. SQLite will let you put the invalid primary key into lang_id but
> only because foreign keys aren't enforced by default.
>
I did not know foreign keys are not enforced by default by SQLite; thanks
for information.
Indeed I did not copy code which creates Lang objects to this test from my
project.
then the reason for the error is that TextValue objects are potentially
> being replaced but the mapping is not emitting a delete for the old
> TextValue, so you'd need to put cascade="all, delete-orphan" on the
> Text._values relationship so that when you assign a new dictionary
> value, the old TextValue objects are deleted.
>
That the old TextValue objects need to be deleted I understand. What I
don't see
is what makes SA specifically blank-out primary key column
'text_value.text_id'?
Asking differently; I would understand if I got some integrity errors while
SA
would be trying to insert new rows with the same keys without first deleting
old rows but I have no idea how SA "came up with the idea" to blank-out
primary key?
> In this specific example, marking the TextValue as deleted ends up gving
> you an UPDATE of TextValue, because the ORM converts an INSERT/DELETE of
> the same primary key into a single UPDATE. But if your dictionary
Is this an implementation detail or official semantics? It's very important
for me
to keep identity of existing TextValue objects and only update values in
their 'value' column.
(The reason it's important is that I'm using sqlalchemy-continuum extension
for automatic
versioning). Is there some preferred way to make sure identity is intact
and modifications
are done through UPDATE and not DELETE/INSERT?
Also, you say that in this specific example there is no DELETE needed yet
there's an error.
Does it mean SA tries to make sure DELETEs would be possible if they were
needed even if
in this specific example they are not needed?
Regards,
Piotr
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