On Aug 16, 2010, at 11:21 AM, bekozi wrote:
> Is it possible to work with set-returning functions in SQLAlchemy
> without using raw SQL? For example, the PostgreSQL/PostGIS function
> ST_Dump (http://bit.ly/culek7) returns a “geometry_dump" set. Using
> ST_Dump in raw SQL goes something like:
>
> SELECT
> ST_Dump(ST_Intersection(data_table1.geom,data_table2.geom)).geom AS
> geom...
>
> In SQLAlchemy an attempt to construct this unsurprisingly yields an
> attribute error:
>
>
> session.query(func.ST_Dump(functions.intersection(Data1.geom,Data2.geom).geom.label('geom'))
> AttributeError: 'Function' object has no attribute 'geom'
any SQL you want can be made available with Python expressions using @compiles:
from sqlalchemy import *
from sqlalchemy.sql import ColumnElement, column
from sqlalchemy.ext.compiler import compiles
class geom(ColumnElement):
def __init__(self, base):
self.base = base
@compiles(geom)
def compile(expr, compiler, **kw):
return compiler.process(expr.base) + ".geom"
data1, data2 = column('data1'), column('data2')
print select([func.ST_Dump(
geom(func.intersection(geom(data1),geom(data2)))
).label('geom')])
> Curious if anyone knows a solution! A search for using set-returning
> functions in SQLAlchemy yielded no obvious solution...
any reason you aren't using GeoAlchemy ?
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