On 08/12/2011 04:46 PM, Michael Bayer wrote:
On Aug 12, 2011, at 9:04 AM, werner wrote:
On 08/12/2011 02:18 PM, werner wrote:
I can't figure out how I could adapt the pk_col function on this page
http://www.sqlalchemy.org/trac/wiki/UsageRecipes/NamingConventions to handle
the Sequence definition needed for e.g. Firebird.
At the point when Column is instantiated I don't have access to "table.name"
and I can't figure it out either how to do it in on_table_attach.
Would appreciate any tips on this.
Did a bit more searching and trying and came up with this:
def pk_col(cls, **kw):
"""Produce a primary key column for a table.
e.g.::
pk_col()
is equivalent to::
Column("id", sa.BigInteger,
doc = "Primary key column for<tablename>",
primary_key=True,
sequence=sa.Sequence('<tablename>_id')
)
"""
kw['primary_key'] = True
c = sa.Column(sa.BigInteger(), sa.Sequence('seq_%s_%s' % (cls.__tablename__,
dbg.pkId)), **kw)
@sa.event.listens_for(c, "before_parent_attach")
def on_table_attach(column, table):
column.name = column.key = dbg.pkId
column.doc = "Primary key column for %r" % table.name
c._creation_order = 0 # forces it to the top when using declarative
return c
I.e. pass "cls" in so I can get to __tablename__.
Is this an o.k. way of doing it or is there a better/cleaner way?
you should be able to set the Sequence name directly in the attach event
(starting with a fake name). not sure how you're using pk_col() above (how it
gets at 'cls').
I had this as part of the declarative base.
@sad.declared_attr
def id(cls):
# use a method so that the pk_col() returned
# here is the one used instead of a copy
return pk_col(cls)
Its also possible to create + attach the Sequence to the Column after the fact
but I don't know that the public API is there for that quite yet. (i think
calling seq._set_parent(column) would be sufficient ...)
Yeap, great.
got this now:
@sa.event.listens_for(c, "before_parent_attach")
def on_table_attach(column, table):
column.name = column.key = dbg.pkId
column.doc = "Primary key column for %r" % table.name
seq = sa.Sequence('seq_%s_%s' % (table.name,
dbg.pkId))
seq._set_parent(column)
I guess I just have to watch out for whenever you provide a public API
for _set_parent.
Thanks
Werner
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