Improving serializers. Adding serializers examples in the notebook

6172e4f0 · Marco Frailis · 7584f427 · 6172e4f0 · 6172e4f0
Commit 6172e4f0 authored 6 years ago by Marco Frailis
--- a/imagedb/serializers.py
+++ b/imagedb/serializers.py

-from composite_field.rest_framework_support import CompositeFieldSerializer
 from rest_framework import serializers
+from composite_field.rest_framework_support import CompositeFieldSerializer


 from imagedb.models import Instrument, NispDetector, Astrometry, NispRawFrame
@@ -17,14 +17,13 @@ class AstrometrySerializer(serializers.ModelSerializer):
  
  class Meta:
    model = Astrometry
-    exclude = ('ctype1_coordinateType',
-               'ctype1_projectionType',
-               'ctype2_coordinateType',
-               'ctype2_projectionType')    
+    exclude = [f.name for g in Astrometry._meta.get_fields() 
+               if hasattr(g, 'subfields') 
+               for f in g.subfields.values()] 

    
 class NispDetectorSerializer(serializers.ModelSerializer):
-  astrometry = AstrometrySerializer(read_only = True)
+  astrometry = AstrometrySerializer()

  class Meta:
    model = NispDetector
@@ -38,12 +37,9 @@ class NispRawFrameSerializer(serializers.ModelSerializer):

  class Meta:
    model = NispRawFrame
-    exclude = ('commandedPointing_rightAscension',
-               'commandedPointing_declination',
-               'commandedPointing_orientation',
-               'imageType_category',
-               'imageType_firstType',
-               'imageType_secondType')
+    exclude = [f.name for g in NispRawFrame._meta.get_fields() 
+               if hasattr(g, 'subfields') 
+               for f in g.subfields.values()]
    depth = 2
    
    
--- a/imagedb_objects.ipynb
+++ b/imagedb_objects.ipynb
@@ -285,12 +285,50 @@
    "obj.delete()"
   ]
  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Serializers\n",
+    "\n",
+    "Let's see some differences between the plain Django serializers and the ModelSerializer class provided by the Django REST framework.\n",
+    "The first example uses the Django core serializers"
+   ]
+  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
-   "source": []
+   "source": [
+    "from django.core import serializers\n",
+    "\n",
+    "data = serializers.serialize('json',NispRawFrame.objects.filter(observationId=53877, \n",
+    "                            filterWheelPosition='Y').order_by('ditherNumber'))\n",
+    "\n",
+    "print(data)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "The following example, instead, uses the Django REST framework ModelSerializer class. In particular, see the file imagedb/serializers.py"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from imagedb.serializers import NispRawFrameSerializer\n",
+    "import json\n",
+    "\n",
+    "frame = NispRawFrameSerializer(NispRawFrame.objects.get(id=1))\n",
+    "print(json.dumps(frame.data, indent=2))\n",
+    "\n"
+   ]
  }
 ],
 "metadata": {

 %% Cell type:markdown id: tags:

 # Data insertion and retrieval with Django models

 In the following we show some examples in order to perform insertions and retrievals of metadata

 %% Cell type:code id: tags:

 ``` python
 from imagedb.models import Instrument

 instrument = Instrument.objects.get(instrumentName='NISP')

 print(instrument.telescopeName)
 ```

 %% Cell type:markdown id: tags:

 ## Creating new objects

 In the following we will create a NispRawFrame object. Since the NispRawFrame must have also a DataCotainer (i.e. a file to reference to), we first create a DataContainer instance.

 We can see also that the fields that we have defined as composite fields provide some synctactic sugar when we initialize them with simple dictionaries.

 %% Cell type:code id: tags:

 ``` python
 from imagedb.models import ImageType, Pointing, NispDetector, DataContainer, NispRawFrame

 from datetime import datetime

 dataFile = DataContainer(
  fileFormat = 'fits',
  formatIdentifier = 'le1.nisprawframe',
  formatVersion = '1.0',
  url = "http://ia2-owncloud.oats.inaf.it/fake/7ff2f203/data/EUC_LE1_NISP_53892-Y-1_20170712T155430.1Z_00.00.fits"
 )

 # We have to save the data container to the DB before assigning it to a NispRawFrame
 dataFile.save()

 image = NispRawFrame(exposureTime = 105,
                     imgNumber = 16,
                     naxis1 = 2040,
                     naxis2 = 2040,
                     imageType = {'category':'SCIENCE',
                                  'firstType':'OBJECT',
                                  'secondType':'STD'},
                     observationDateTime = datetime.strptime("2025-06-21T18:27:23.000001",
                                                             "%Y-%m-%dT%H:%M:%S.%f"),
                     observationId = 53892,
                     ditherNumber = 1,
                     instrument = instrument,
                     commandedPointing = {'rightAscension':8.48223045516,
                                          'declination':8.48223045516,
                                          'orientation':64.8793517547},
                     filterWheelPosition = "Y",
                     grismWheelPosition = "OPEN"
                    )



 image.frameFile = dataFile
 ```

 %% Cell type:markdown id: tags:

 Before saving an object, its surrogate key is still empty, i.e. equal to None

 %% Cell type:code id: tags:

 ``` python
 print(image.id)
 image.save()
 print(image.id)
 ```

 %% Cell type:code id: tags:

 ``` python
 # We can start creating a detector

 d11 = NispDetector(detectorId = "11", gain = 1.0, readoutNoise = 0.0, rawFrame = image)
 d11.save()

 # Or we can use the create() in order to create and save immediately the new object
 NispDetector.objects.create(detectorId = "12", gain = 1.0, readoutNoise = 0.0, rawFrame = image)

 # or we can create the detector starting from the NispRawFrame, using the reversed relationship,
 # using again the create method

 image.detectors.create(
  detectorId = "13",
  gain = 1.0,
  readoutNoise = 0.0
 )
 ```

 %% Cell type:markdown id: tags:

 ## Objects retrieval

 To retrieve objects from your database, construct a **QuerySet** via a **Manager** on your model class.

 A **QuerySet** represents a collection of objects from your database. It can have zero, one or many filters. Filters narrow down the query results based on the given parameters. In SQL terms, a **QuerySet** equates to a **SELECT** statement, and a **filter** is a limiting clause such as **WHERE** or **LIMIT**.

 You get a **QuerySet** by using your model’s **Manager**. Each model has at least one Manager, and it’s called **objects** by default.

 The simplest way to retrieve objects from a table is to get all of them. To do this, use the **all()** method on a **Manager**:

 %% Cell type:code id: tags:

 ``` python
 len(NispRawFrame.objects.all())
 ```

 %% Cell type:markdown id: tags:

 But usually we want to filter the results. For this purpose we can use the **filter** method, both provided by the **Manager** and the **QuerySet**


 %% Cell type:code id: tags:

 ``` python
 # Retrieving all frames with observation id 53877 and filter Y
 # and ordering the results by the ditherNumber

 result = NispRawFrame.objects.filter(observationId=53877,
                                     filterWheelPosition='Y').order_by('ditherNumber')

 for obj in result:
    print(obj.observationId, obj.filterWheelPosition, obj.ditherNumber)
 ```

 %% Cell type:markdown id: tags:

 We can also limit the number of results of a **QuerySet**, using the Python array-slice syntax:

 %% Cell type:code id: tags:

 ``` python
 from datetime import datetime

 # Retrieving all NISP raw frames with observation date and time
 # greater then or equal to 2026-06-22T17:00
 len(NispRawFrame.objects.filter(observationDateTime__gte=datetime(2025,6,22,17,0)))
 ```

 %% Cell type:code id: tags:

 ``` python
 # Now limiting the result to 5 items

 len(NispRawFrame.objects.filter(observationDateTime__gte=datetime(2025,6,22,17,0))[:5])
 ```

 %% Cell type:markdown id: tags:

 Keyword argument queries – in filter(), etc. – are “AND”ed together. If you need to execute more complex queries (for example, queries with OR statements), you can use **Q objects**.

 %% Cell type:code id: tags:

 ``` python
 # Now retrieving all frames with observation ids 53877 and 54349 and filter H
 from django.db.models import Q

 result = NispRawFrame.objects.filter(Q(observationId=53877) | Q(observationId=54349),
                                     filterWheelPosition='H').order_by('observationId', 'ditherNumber')

 for obj in result:
    print(obj.observationId, obj.filterWheelPosition, obj.ditherNumber)
 ```

 %% Cell type:markdown id: tags:

 We can also traverse relations

 %% Cell type:code id: tags:

 ``` python
 # Getting all NispDetectors whose frame observation id is 53877 or 54349 and
 # filterWheelPosition is Y.
 # Notice that here we also use the 'in' operator

 result = NispDetector.objects.filter(rawFrame__observationId__in=[53877, 54349],
                                     rawFrame__filterWheelPosition='Y').order_by(
                                     'rawFrame__observationId', 'rawFrame__ditherNumber',
                                     'detectorId')

 for obj in result:
    print(obj.rawFrame.observationId, obj.rawFrame.ditherNumber, obj.detectorId)
 ```

 %% Cell type:code id: tags:

 ``` python
 # OR we can find the NispRawFrame whose referenced file url contains "LE1_NISP_52926-J-2"

 result = NispRawFrame.objects.filter(frameFile__url__contains="LE1_NISP_52926-J-2")

 for obj in result:
    print(obj.observationId, obj.frameFile.url)
 ```

 %% Cell type:markdown id: tags:

 In order to retrive a single object, instead of using **filter** we can use the **get** method. This method returns one object and raise exceptions if no object is found or if multiple objects satisfy the query

 %% Cell type:code id: tags:

 ``` python
 obj = NispRawFrame.objects.get(observationId=53892)

 # now we delete such object from the database

 obj.delete()
 ```

+%% Cell type:markdown id: tags:
+
+## Serializers
+
+Let's see some differences between the plain Django serializers and the ModelSerializer class provided by the Django REST framework.
+The first example uses the Django core serializers
+
+%% Cell type:code id: tags:
+
+``` python
+from django.core import serializers
+
+data = serializers.serialize('json',NispRawFrame.objects.filter(observationId=53877,
+                            filterWheelPosition='Y').order_by('ditherNumber'))
+
+print(data)
+```
+
+%% Cell type:markdown id: tags:
+
+The following example, instead, uses the Django REST framework ModelSerializer class. In particular, see the file imagedb/serializers.py
+
 %% Cell type:code id: tags:

 ``` python
+from imagedb.serializers import NispRawFrameSerializer
+import json
+
+frame = NispRawFrameSerializer(NispRawFrame.objects.get(id=1))
+print(json.dumps(frame.data, indent=2))
+
 ```