On Mon, Jul 22, 2019, at 10:51 PM, Jonathan Vanasco wrote:
>
>
> On Monday, July 22, 2019 at 9:36:10 PM UTC-4, Mike Bayer wrote:
>>
>> likely , the "create_constraint" flag should default to False for booleans
>> and enums. I think it was a mistake to default these to true, I think people
>> usually don't care.
>
> Everything you said was apparent to me, but I'm a seasoned SqlAlchemy user. I
> dove into the docs and didn't see warning dragons or anything that would
> suggest this happens alongside the Alembic or Boolean docs... this seemed
> like something that would trip up inexperienced users.
>
> I'm assuming I never saw this before on Postgres or MySql because sqlite
> requires a constraint to mimic boolean behaviors as there is no native type,
> but I usually reflect tables on those platforms so that could be the reason.
>
> Would it make sense to default the constraint name to something like
> "sa_autoname_xxxxx' where xxxx is a random hash?
I would say no, because you are asking SQLAlchemy to make a guess a a name when
the database would normally be doing this; however, that's not taking place
since you've explicitly told it about a naming convention you'd like to use! if
this naming convention should include "sa_autoname_xxxx" that should be
explicit within the naming convention.
this points to that, you probably don't want to be using %(constraint_name)s in
your convention. Probably some other kind of token, like
%({constraint_name:sa_autoname_12345})s or something, that is, some as-yet not
defined feature to add to naming convention that allows constraint_name to have
a fallback of some kind.
However, you can make this feature yourself, as naming conventions allow custom
callables:
https://docs.sqlalchemy.org/en/13/core/constraints.html#constraint-naming-conventions
it's near the end, and is a little weird in this case, but looks like:
def auto_constraint_name(constraint, table):
if constraint.name is None or constraint.name == "_unnamed_":
return "sa_autoname_%s" % str(uuid.uuid4())[0:5]
else:
return constraint.name
NAMING_CONVENTION = {
"auto_constraint_name": auto_constraint_name,
"ix": 'ix_%(column_0_label)s',
"uq": "uq_%(table_name)s_%(column_0_name)s",
"ck": "ck_%(table_name)s_%(auto_constraint_name)s",
"fk": "fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s",
"pk": "pk_%(table_name)s"
}
_metadata = sqlalchemy.MetaData(naming_convention=NAMING_CONVENTION)
as always, this is not well documented, especially the weirdness with
"_unnamed_" which is a default token of sorts, and if you have any time to help
at all creating an example and/or working out use cases to make this easier for
this as it should likely be the default for "ck", let me know.
>
>
>
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