Hey,
I have a model which monitors the prices of certain items at certain
markets daily.
precios/models:
...
class Prueba(Approvable):
mercado = models.ForeignKey(Mercado)
producto = models.ForeignKey(Producto)
fecha = models.DateField()
minimo = models.DecimalField(max_digits=10,decimal_places=2)
maximo = models.DecimalField(max_digits=10,decimal_places=2)
...
Now I want to be able to get the monthly average prices over a certain
period of time. At first I tried this (using postgresql):
queryset=PrecioPrueba.objects.filter(producto=producto).filter
(mercado=mercado).filter(fecha__range[start_date,end_date]).extra
(select={'fecha':"date_trunc('"+frecuencia+'",fecha)"}).values
('fecha','producto','mercado','maximo','minimo').annotate(maximo=Avg
('maximo'),minimo=Avg('minimo')).order_by('fecha')
but that just gave me all the values with the date set to the first of
the month, so I figured django isn't up for the job yet. Instead I
tried doing it this way:
...
from django.db import connection
cursor = connection.cursor()
cursor.execute("select producto_id as producto, mercado_id as mercado,
date_trunc('month',fecha) as fecha, avg(maximo) as maximo, avg(minimo)
as minimo from precios_prueba where producto_id = %s and mercado_id =
%s group by date_trunc('month',fecha), producto_id, mercado_id order
by fecha;", [producto,mercado])
queryset=[]
for row in cursor.fetchall():
row_dic={'fecha':row[2],'maximo':row[3],'minimo':row
[4],'producto':row[0],'mercado':row[1]}
queryset.append(row)
...
This works in the shell, but using it on a real live site I get the
error:
can't adapt
without any additional infos, other than that it originates from the
psycopg2-connection.
Any clues?
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