feat: add field to track the latest advisory for an avid

Signed-off-by: Keshav Priyadarshi <git@keshav.space>

Author: keshav-space

vulnerabilities/models.py

@@ -2886,11 +2886,7 @@ def latest_for_avid(self, avid: str):
         )
 
     def latest_per_avid(self):
-        return self.order_by(
-            "avid",
-            F("date_collected").desc(nulls_last=True),
-            "-id",
-        ).distinct("avid")
+        return self.filter(is_latest=True)
 
     def latest_for_avids(self, avids):
         return self.filter(avid__in=avids).latest_per_avid()
@@ -3007,6 +3003,7 @@ class AdvisoryV2(models.Model):
         max_length=200,
         blank=False,
         null=False,
+        db_index=True,
         help_text="Unique ID for the datasource used for this advisory ." "e.g.: nginx_importer_v2",
     )
 
@@ -3090,6 +3087,14 @@ class AdvisoryV2(models.Model):
         help_text="UTC Date on which the advisory was collected",
     )
 
+    is_latest = models.BooleanField(
+        default=False,
+        blank=False,
+        null=False,
+        db_index=True,
+        help_text="Indicates whether this is the latest version of the advisory identified by its AVID.",
+    )
+
     original_advisory_text = models.TextField(
         blank=True,
         null=True,
@@ -3142,6 +3147,11 @@ class AdvisoryV2(models.Model):
     class Meta:
         unique_together = ["datasource_id", "advisory_id", "unique_content_id"]
         ordering = ["datasource_id", "advisory_id", "date_published", "unique_content_id"]
+        constraints = [
+            models.UniqueConstraint(
+                fields=["avid"], condition=Q(is_latest=True), name="unique_latest_per_avid"
+            )
+        ]
         indexes = [
             models.Index(
                 fields=["avid", "-date_collected", "-id"],