Using Django ArrayField to Store Dates and Value - django

Question

I'm currently having a hard time wrapping my head around Django's Array Field. What i'm hoping to do is have an array that looks something like this:
Price(close=[
[1/1/2018, 3.00],
[1/2/2018, 1.00],
])
It's basically an array that stores a date followed by a corresponding value tied to that date. However, thus far my model looks like this:
class Price(models.Model):
close = ArrayField(
models.DecimalField(max_digits=10, decimal_places=4),
size=365,
)
I am not certain how to create an array with two different types of fields, one DateTime, the other decimal. Any help would be much appreciated.

Answer 1

You can't mix types stored in the ArrayField. [1] I recommend you to change model schema (aka Database normalization [2]).
This is my suggestion:
from django.db import models
class Price(models.Model):
pass
class PriceItem(models.Model):
datetime = models.DateTimeField()
ammount = models.DecimalField(max_digits=10, decimal_places=4)
price = models.ForeignKey(Price, on_delete=models.CASCADE)
[1] https://stackoverflow.com/a/8168017/752142
[2] https://en.wikipedia.org/wiki/Database_normalization

Answer 2

It depends on how important it is to the model.
postgresql provides composite types
The generous contributor of psycopg2 (django's posgresql driver) is supporting it,
define this type in postgresql:
CREATE TYPE date_price AS (
start date,
float8 price
);
and using the methods described here to implement CompositeField
from django.db import models
from django.contrib.postgres.fields import ArrayField
from django.db import connection
from psycopg2.extras import register_composite
# register the composite
register_composite('date_price', connection.cursor().cursor)
# CompositeField implementation here . . . . . .
class DatePriceField(CompositeField):
'''
DatePriceField specifics
'''
pass
class Price(models.Model):
close = ArrayField(base_field=DatePriceField(), size=365,)
I am going to follow this route and update soon.