Fix cfbot CI status showing incorrect task counts

When cfbot retries failed tasks, it creates multiple tasks with the same `(branch_id, position)` but different `task_id` values. This caused the CI status display to show incorrect counts like "10/11" instead of "10/10".

This fix changes the unique constraint from `task_id` to `(branch_id, position)` and updates the cfbot ingestion logic to replace older tasks with newer ones when retries occur. The `INSERT ... ON CONFLICT` now uses the position-based constraint to keep only the most recent task for each position.

Author: JelteF

pgcommitfest/commitfest/migrations/0015_cfbot_duplicate_task_fix.py

@@ -0,0 +1,44 @@
+# Generated by Django 4.2.19 on 2025-08-17 16:29
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("commitfest", "0014_add_paused_cfbot_task_state"),
+    ]
+
+    operations = [
+        # Remove duplicate tasks keeping the one with the latest modified time
+        migrations.RunSQL(
+            """
+            DELETE FROM commitfest_cfbottask
+            WHERE id IN (
+                SELECT id FROM (
+                    SELECT id,
+                           ROW_NUMBER() OVER (
+                               PARTITION BY branch_id, position
+                               ORDER BY modified DESC
+                           ) as rn
+                    FROM commitfest_cfbottask
+                ) t
+                WHERE rn > 1
+            );
+            """,
+            reverse_sql="",
+        ),
+        # Remove unique constraint from task_id field
+        migrations.AlterField(
+            model_name="cfbottask",
+            name="task_id",
+            field=models.TextField(),
+        ),
+        # Add unique constraint on (branch_id, position)
+        migrations.AddConstraint(
+            model_name="cfbottask",
+            constraint=models.UniqueConstraint(
+                fields=["branch_id", "position"],
+                name="commitfest_cfbottask_branch_position_unique",
+            ),
+        ),
+    ]

pgcommitfest/commitfest/models.py

@@ -842,7 +842,7 @@ class CfbotTask(models.Model):
     # given that we might need to change CI providers at some point, and that
     # CI provider might use e.g. UUIDs, we prefer to consider the format of the
     # ID opaque and store it as text.
-    task_id = models.TextField(unique=True)
+    task_id = models.TextField()
     task_name = models.TextField(null=False)
     patch = models.ForeignKey(
         Patch, on_delete=models.CASCADE, related_name="cfbot_tasks"
@@ -853,3 +853,11 @@ class CfbotTask(models.Model):
     status = models.TextField(choices=STATUS_CHOICES, null=False)
     created = models.DateTimeField(auto_now_add=True)
     modified = models.DateTimeField(auto_now=True)
+
+    class Meta:
+        constraints = [
+            models.UniqueConstraint(
+                fields=["branch_id", "position"],
+                name="commitfest_cfbottask_branch_position_unique",
+            )
+        ]

pgcommitfest/commitfest/views.py

@@ -1457,8 +1457,11 @@ def cfbot_ingest(message):
                                                 position, status,
                                                 created, modified)
                         VALUES (%s, %s, %s, %s, %s, %s, %s, %s)
-                        ON CONFLICT (task_id) DO UPDATE
-                            SET status = EXCLUDED.status,
+                        ON CONFLICT (branch_id, position) DO UPDATE
+                            SET task_id = EXCLUDED.task_id,
+                                task_name = EXCLUDED.task_name,
+                                status = EXCLUDED.status,
+                                created = EXCLUDED.created,
                                 modified = EXCLUDED.modified
                         WHERE commitfest_cfbottask.modified < EXCLUDED.modified""",
                 (