Hi,
Based on some posts I was able to find scouring Google, I was trying
to implement a custom type (GeometryType) for the PostGIS "GEOMETRY"
column.
Now, I should point out that I am not using sqlalchemy to build the
DDL, since the geometry columns are indirectly created by invoking
stored procedures (and I couldn't really figure out a clean way to
handle that). I am, however, using these Geometry types in my Table
instances [mapping to already-created tables].
The problem is that I'd like to have sqlalchemy return KML for all
geometry types by default, but I don't know how to setup my type to
specify a SQL function that needs to be applied to the column in the
select clause. Is this possible? Alternatively, it would be
*perfect* to have additional *_kml properties added to the result
objects (one for each GEOMETRY column), but this seems even more
complex (?).
Here is my simple type class:
class GeometryType(sa.types.TypeEngine):
def __init__(self, SRID, typeName, dimension):
super(GeometryType, self).__init__()
self.mSrid = SRID
self.mType = typeName.upper()
self.mDim = dimension
def __repr__(self):
return "%s:%s-%s(%s)" % (self.__class__.__name__, self.mType,
self.mDim, self.mSrid)
def get_col_spec(self):
return "GEOMETRY"
def convert_bind_param(self, value, engine):
if not value:
return None
else:
return 'GeomFromText(\'%s\',%s)' % (value, self.mSrid)
def convert_result_value(self, value, engine):
return 'AsKml(%s)' % value
I was expecting my convert_result_value method to operate on the SQL,
but I am assuming from looking at the generated SQL that this method
is actually going to operate on the raw data that was returned from
SQL. So, is there a way to accomplish what I want?
Thanks in advance!
Hans
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