models: fix EventRecord default saved_at timestamp type

CHANGELOG.rst

@@ -5,6 +5,7 @@ Changelog
 -------------------
 
 - Aggregator field on the Application admin was wrongly required.
+- Fix default `saved_at` for event records
 
 
 0.6.14 (2019-10-18)

mds/migrations/0057_pre_event_record_auto_now.py

@@ -0,0 +1,18 @@
+# Generated by Django 2.1.5 on 2019-10-23 14:04
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('mds', '0056_post_compliance_saved_at_not_nullable'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='eventrecord',
+            name='saved_at',
+            field=models.DateTimeField(auto_now=True, db_index=True),
+        ),
+    ]

mds/models.py

@@ -7,7 +7,6 @@
 from django import forms
 from django.contrib.gis.db import models as gis_models
 from django.contrib.postgres import fields as pg_fields
-from django.contrib.postgres import functions as pg_functions
 from django.core.exceptions import ValidationError
 from django.db import models
 from django.db.models import Count, Prefetch, Q
@@ -248,8 +247,7 @@ def gps_point_as_geojson(self):
 class EventRecord(models.Model):
     timestamp = models.DateTimeField(db_index=True)
     point = gis_models.PointField(blank=True, null=True)
-    # For synchronisation purposes (polling on this field)
-    saved_at = models.DateTimeField(default=pg_functions.TransactionNow, db_index=True)
+    saved_at = models.DateTimeField(auto_now=True, db_index=True)
     # For KPIs, know when the event was seen by an aggregator the first time
     first_saved_at = models.DateTimeField(blank=True, null=True)
     source = UnboundedCharField(