Thanks for the reply. I had implemented this feature about two months ago,
and I had forgotten myself. I had originally used this:
def rand_hex_str():
return '%016x' % random.getrandbits(64)
# using event listener to force foreign key definitions to use 'alter
statements'
def fk_constraint_name(const, table):
fk_name = 'fk_' + rand_hex_str() # generates a foreign key constraint
like: fk_ABC0234DEF
const.name = fk_name
const.use_alter = True # generate alter statements.
event.listen(ForeignKeyConstraint, "before_parent_attach",
fk_constraint_name)
Later, I replaced the sqlalchemy.ForiegnKey class with this wrapper
function before the model definitions start using foreign key relationships:
orig_fkey_class = sqlalchemy.ForeignKey
def use_alter_fkey_func(*args, **kwargs):
if 'name' not in kwargs:
kwargs['name'] = 'fk_' + rand_hex_str()
if 'use_alter' not in kwargs:
kwargs['use_alter'] = True
return orig_fkey_class(*args, **kwargs)
sqlalchemy.ForeignKey = use_alter_fkey_func
Is there a drawback to replacing the sqlAlchemy ForeignKey class with this
wrapper function instead of using an event?
On Wednesday, August 27, 2014 5:20:35 AM UTC-7, Michael Bayer wrote:
>
> you can alter how MetaData things are built up using the
> after_parent_attach event:
>
>
> http://docs.sqlalchemy.org/en/rel_0_9/core/events.html?highlight=after_parent_attach#sqlalchemy.events.DDLEvents.after_parent_attach
>
>
> apply the event to ForeignKey and set use_alter=True for all of them as
> they come in.
>
>
> On Aug 26, 2014, at 10:03 PM, Bala Ramakrishnan <bal...@gmail.com
> <javascript:>> wrote:
>
> To generate an 'alter table ' statement for foreign key constraints, we
> have to specify use_alter=True for the ForeignKey class.
>
> Is there a global setting or via setting up some kind of event call back
> to generate the alter statements by default for all foreign key constraints
> instead of setting them for each relationship?
>
> I am trying to find a comparable setting with Java Hibernate.
>
> -Bala
>
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