CODEWITHSUNDEEP
djangodjango-rest-frameworkdjango-serializer
kh_one
kh_one

Reputation: 257

Serialized data from RetrieveAPIView arriving jumbled

I have a serializer that takes prices and matching transaction dates from a model and sends it on via RetrieveAPIView, to be picked up by a ChartJS price chart on the other end:

class MyPriceSerializer(serializers.Serializer):
    prices = serializers.SerializerMethodField()
    price_dates = serializers.SerializerMethodField()

    def get_prices(self, obj):
        return obj.prices.values_list('price', flat=True)

    def get_price_dates(self, obj):
        qs = obj.prices.all()
        qs = qs.extra(select={'datestr':"to_char(price_date, 'DD Mon HH24:MI')"})
        return qs.values_list('datestr', flat=True)

class ChartData(RetrieveAPIView):
    queryset = Market.objects.all().prefetch_related('prices')
    authentication_classes = []
    permission_classes = []
    serializer_class = MyPriceSerializer

My problem is that the data is arriving in a jumbled order, as can be seen from the price_dates here:

HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

{
    "prices": [
        0.55,
        0.57,
        0.5,
        0.43,
        0.45,
        0.57,
        0.55,
        0.48,
        0.4,
        0.52,
        0.6,
        0.52,
        0.45,
        0.43
    ],
    "price_dates": [
        "24 Jul 12:08",
        "24 Jul 12:08",
        "24 Jul 12:08",
        "24 Jul 12:09",
        "24 Jul 12:11",
        "24 Jul 12:08",
        "24 Jul 12:08",
        "24 Jul 12:08",
        "24 Jul 12:09",
        "24 Jul 12:08",
        "24 Jul 12:08",
        "24 Jul 12:08",
        "24 Jul 12:08",
        "24 Jul 12:09"
    ]
}

Why is that?

Further details: I've confirmed that the prices and price dates are in order in the model itself. For database, I'm using PostgreSQL11.

Upvotes: 0

Views: 46

Answers (1)

anjaneyulubatta505
anjaneyulubatta505

Reputation: 11675

You should use order_by on query to get results in correct order.

    def get_prices(self, obj):
        return obj.prices.order_by('price_date').values_list('price', flat=True)

    def get_price_dates(self, obj):
        qs = obj.prices.all().order_by('price_date')
        qs = qs.extra(select={'datestr':"to_char(price_date, 'DD Mon HH24:MI')"})
        return qs.values_list('datestr', flat=True)

Upvotes: 1

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